1. (a) When solid calcium nitrate is heated, brown fumes of nitrogen dioxide, NO2, are seen and

the solid remaining after decomposition is calcium oxide.

(i) Write a balanced equation for the thermal decomposition of calcium nitrate.

......................................................................................................................... (2)

(ii) Describe the changes you would see when cold water is added drop by drop to cold

calcium oxide and give the chemical equation for the reaction.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (3)

(iii) State whether barium nitrate will decompose more easily or less easily than

calcium nitrate on heating with a Bunsen burner.

......................................................................................................................... (1)

(iv) Account for the trend in the thermal stability of the nitrates of the elements in

group 2.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (3)

(b) The brown fumes in part (a) are not pure NO2 but a mixture of N2O4 and NO2.

N2O4(g) 2NO2(g)

Pale yellow dark brown

A transparent glass syringe was filled with the gaseous mixture of N2O4 and NO2 and its

tip sealed. When the piston of the syringe was rapidly pushed well into the body of the

syringe, thereby compressing the gas mixture considerably, the colour of the gas became

momentarily darker but them became lighter again.

(i) Suggest why compressing the gases causes the mixture to darken.

.........................................................................................................................

......................................................................................................................... (1)

(ii) Explain why the mixture turns lighter on standing.

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (2)

(iii) Write an expression for the equilibrium constant, Kp, for this equilibrium.

(1)

(iv) 1.0 mole of N2O4 was allowed to reach equilibrium at 400K. At equilibrium the

partial pressure of N2O4 was found to be 0.15 atm.

Given that the equilibrium constant Kp for this reaction is 48 atm, calculate the

partial pressure of NO2 in the equilibrium mixture.

(3)

(Total 16 marks)

2. Adrenalin is a hormone which raises blood pressure, increases the depth of breathing and delays

fatigue in muscles, thus allowing people to show great strength under stress.

Benzedrine is a pharmaceutical which stimulates the central nervous system in a similar manner

to adrenalin.

CH CH(CH ) NH2 2 2 33

HO

HO CH(OH) CH N

H

CH

Benzedrine Adrenalin

(a) (i) On the structure for benzedrine mark with a (*) any asymmetric carbon atom that

causes chirality. (1)

(ii) Suggest why adrenalin is more soluble in water than is benzedrine.

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(b) Give the structural formulae of the organic products obtained when benzedrine reacts

with:

(i) an aqueous acid such as dilute hydrochloric acid;

(1)

(ii) ethanoyl chloride in the absence of a catalyst;

(1)

(iii) excess ethanoyl chloride in the presence of the catalyst anhydrous aluminium

chloride.

(2)

(d) It is possible to eliminate a molecule of water from adrenalin which for the purpose of

this question may be represented as R–CH(OH)–CH2–NH–CH3. Draw the structural

formulae of the two stereoisomers produced.

(2)

(e) The mass spectra of both benzedrine and adrenalin have a peak at a mass/charge ratio of

44. Draw the structure of the species which give these peaks.

(i) in benzedrine;

(1)

(ii) in adrenalin.

(1)

(Total 11 marks)

3. (a) (i) Calculate the concentration, in mol dm–3

, of a solution of hydrochloric acid, HCl,

which has a pH of 1.13.

(1)

(ii) Calculate the concentration, in mol dm–3

, of a solution of chloric(l) acid, HOCl,

which has a pH of 4.23.

Chloric(l) acid is a weak acid with Ka = 3.72 × 10–8

mol dm–3

.

(4)

(b) The pH of 0.100 mol dm–3

sulphuric acid is 0.98.

(i) Calculate the concentration of hydrogen ions, H+, in this solution.

(1)

(ii) Write equations to show the two successive ionisations of sulphuric acid, H2SO4, in

water.

......................................................................................................................

...................................................................................................................... (2)

(iii) Suggest why the concentration of hydrogen ions is not 0.20 mol dm–3

in 0.100 mol

dm–3

sulphuric acid.

......................................................................................................................

...................................................................................................................... (1)

(c) Many industrial organic reactions produce hydrogen chloride as an additional product.

This can be oxidised to chlorine by the Deacon process:

4HCl(g) + O2(g) 2Cl2(g) + 2H2O(g) H = –115 kJ mol–1

.

0.800 mol of hydrogen chloride was mixed with 0.200 mol of oxygen in a vessel of

volume 10.0 dm3 in the presence of a copper(I) chloride catalyst at 400 ºC. At

equilibrium it was found that the mixture contained 0.200 mol of hydrogen chloride.

(i) Write an expression for the equilibrium constant Kc.

(1)

(ii) Calculate the value of Kc at 400 ºC.

(4)

(d) State and explain the effect, if any, on the position of equilibrium in (c) of:

(i) decreasing the temperature;

......................................................................................................................

......................................................................................................................

...................................................................................................................... (2)

(ii) decreasing the volume;

......................................................................................................................

......................................................................................................................

...................................................................................................................... (2)

(iii) removing the catalyst.

......................................................................................................................

......................................................................................................................

...................................................................................................................... (2)

(Total 20 marks)

4. This question concerns the three isomers A, B and C, each of which has a relative molecular

mass of 134.

C C

O

H

O

CH

CH CH OH

CH CHCH

CH

2

2

2 23

A B

C

(a) The mass spectrum of substance A is shown below. Identify the species responsible for

the peaks labelled 1, 2 and 3.

Peak 1 .........................................................................................................................

Peak 2 .........................................................................................................................

Peak 3 ......................................................................................................................... (3)

(b) The infra-red spectra of two of these substances were also measured.

(i) Use the table and the spectra below to identify which spectrum is that of

substance C.

Bond

Wavenumber

/ cm–1

Bond

Wavenumber

/ cm–1

C—H (arenes) 3000-3100 O––H (hydrogen bonded) 3200-3570

C—H (alkanes) 2850-3000 O––H (not hydrogen

bonded)

3580-3650

C==O 1680-1750 C==C (arenes) 1450-1600

The spectrum of substance C is spectrum number .......................................... (1)

(ii) Give one reason for your choice.

...................................................................................................................... (1)

(iii) Give one other reason why the other spectrum could not be that of substance C.

......................................................................................................................

...................................................................................................................... (1)

100

80

60

40

20

0

Rela

tive i

nte

nsi

ty

25 50 75 100 125m/e

1

2

3

100

50

04000 3000 2000 1500 1000

Wavenumber/cm–1

Tra

nsm

itta

nce

100

50

04000 3000 2000 1500 1000

Wavenumber/cm–1

Tra

nsm

itta

nce

(c) State which of the substances A, B and C will react with the following reagents and state

what would be observed.

(i) Bromine dissolved in hexane.

Substance(s) .....................................................................................................

Observation ...................................................................................................... (2)

(ii) A warm ammoniacal solution of silver nitrate.

Substance(s) .....................................................................................................

Observation ...................................................................................................... (2)

(iii) 2,4-dinitrophenylhydrazine solution.

Substance(s) .....................................................................................................

Observation ...................................................................................................... (3)

(iv) Give the structural formula of the organic product(s) obtained in (c)(i).

(1)

(v) Give the structural formula of the organic product(s) obtained in (c)(ii).

(1)

(Total 18 marks)

5. The kinetics of the hydrolysis of the halogenoalkane RCH2Cl with aqueous sodium hydroxide

(where R is an alkyl group) was studied at 50 ºC. The following results were obtained:

Experiment [RCH2Cl] [OH–] Initial rate/mol dm

–3 s

–1

1 0.050 0.10 4.0 × 10–4

2 0.15 0.10 1.2 × 10–3

3 0.10 0.20 1.6 × 10–3

(i) Deduce the order of reaction with respect to the halogenoalkane, RCH2Cl, and with

respect to the hydroxide ion, OH–, giving reasons for your answers.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................ (4)

(ii) Hence write the rate equation for the reaction.

................................................................................................................................ (1)

(iii) Calculate the value of the rate constant with its units for this reaction at 50 ºC.

(2)

(iv) Using your answer to part (ii), write the mechanism for this reaction.

(3)

(Total 10 marks)

6. The reaction between sulphur dioxide and oxygen is a dynamic equilibrium.

2SO2 + O2 2SO3 H = –196 kJmol–1

(a) Explain what is meant by dynamic equilibrium.

..................................................................................................................................

..................................................................................................................................

.................................................................................................................................. (2)

(b) In the table below state the effect on this reaction of increasing the temperature and of

increasing the pressure.

Effect on the rate of the

reaction

Effect on the position of

equilibrium

Increasing the

temperature

Increases

Increasing the pressure

(3)

(c) This reaction is one of the steps in the industrial production of sulphuric acid. The

normal operating conditions are a temperature of 450 °C, a pressure of 2 atmospheres

and the use of a catalyst.

Justify the use of these conditions.

(i) A temperature of 450 °C:

......................................................................................................................

......................................................................................................................

...................................................................................................................... (3)

(ii) A pressure of 2 atmospheres:

......................................................................................................................

......................................................................................................................

...................................................................................................................... (2)

(iii) A catalyst:

......................................................................................................................

......................................................................................................................

...................................................................................................................... (1)

(d) Give the name of the catalyst used.

.................................................................................................................................. (1)

(e) Give one large scale use of sulphuric acid.

.................................................................................................................................. (1)

(Total 13 marks)

7. (a) What is meant by the term weak acid?

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (2)

(b) A weak acid, represented by HA, dissociates in water according to the equation:

HA(aq) + H2O(l) H3O+(aq) + A–(aq)

Write an expression for the dissociation constant, Ka, for HA.

(1)

(c) 25 cm3 of 1.00 mol dm

–3 aqueous HA, was titrated with 1.00 mol dm

–3 aqueous sodium

hydroxide and the pH measured throughout. The titration curve is shown below.

14

12

10

8

6

4

2

010 20 30 40 50

Volume of sodium hydroxide added / cm

pH

3

Use the titration curve to find:

(i) the value of the pH at the end point of the titration.

............................................................................................................................ (1)

(ii) the pH of an aqueous solution of the salt NaA.

............................................................................................................................ (1)

(iii) the value of pKa for the acid HA and, hence the value Ka.

pKa ...................................................................................................................

Ka .....................................................................................................................

(2)

(d) Some of the solutions made during this titration would act as buffer solutions.

(i) What is meant by the term buffer solution?

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(ii) Use the titration curve to find:

the range of pH values over which this mixture acts as a buffer;

from .................................................... to .................................................... (1)

the pH of the most efficient buffer solution.

............................................................................................................................ (1)

(e) Suggest, with reasoning, whether methyl orange or phenolphthalein would be the better

indicator for this titration.

Choice ........................................................................................................................

Reasoning ..................................................................................................................

....................................................................................................................................

.................................................................................................................................... (3)

(f) Explain why, as the titration proceeds, the flask becomes warm but not as warm as it

would in a similar titration using 1.00 mol dm–3

solutions of hydrochloric acid and

sodium hydroxide.

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (3)

(g) A different monobasic weak acid has a dissociation constant of 1.8 × 10– 5 mol dm

–3.

(i) Define pH.

............................................................................................................................ (1)

(ii) Calculate the pH of a 1.00 mol dm–3

aqueous solution of this acid.

(3)

(Total 21 marks)

8. In the vapour phase sulphur trioxide dissociates:

2SO3(g) 2SO2(g) + O2(g)

(a) (i) Write an expression for Kp for this dissociation.

(1)

(ii) At a particular temperature, 75% of the sulphur trioxide is dissociated, producing a

pressure of 10 atm. Calculate the value of Kp at this temperature paying, attention

to its units.

(5)

(b) Solid vanadium(V) oxide, V2O5, is an effective catalyst for this reaction. State the effect

of using double the mass of catalyst on:

(i) the position of the equilibrium;

............................................................................................................................

............................................................................................................................ (1)

(ii) the value of Kp.

............................................................................................................................

............................................................................................................................ (1)

(Total 8 marks)

9. (a) (i) Define the term standard enthalpy of combustion.

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................ (3)

(ii) The values for the standard enthalpy of combustion of graphite and carbon

monoxide are given below:

Hc /kJ mol–1

C (graphite) –394

CO(g) –283

Use these data to find the standard enthalpy change of formation of carbon

monoxide using a Hess‘s law cycle.

C(graphite) + 2

1O2(g) CO(g)

(3)

(iii) Suggest why it is not possible to find the enthalpy of formation of carbon

monoxide directly.

............................................................................................................................

............................................................................................................................ (1)

(iv) Draw an enthalpy level diagram below for the formation of carbon monoxide from

graphite.

(1)

(b) Natural gas consists of methane, CH4. When methane burns completely in oxygen the

reaction occurs as shown in the equation

CH4(g) + 2O2(g) CO2(g) + 2H2O(l) Hc = –890 kJ mol–1

Methane does not burn unless lit.

Use this information to explain the difference between thermodynamic and kinetic

stability.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (4)

(Total 12 marks)

10. (a) An alcohol with the molecular formula C4H9OH is chiral.

(i) Explain what is meant by the term chiral.

............................................................................................................................

............................................................................................................................ (2)

(ii) Draw two diagrams to clearly represent the optical isomers that result from the

chirality of this alcohol.

(2)

(iii) Explain how you could distinguish between these two isomers experimentally.

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(b) Alcohols react with carboxylic acids to form esters.

(i) Write an equation for a typical esterification reaction.

............................................................................................................................ (1)

(ii) Suggest how this type of reaction could be used to form polyesters.

Experimental details are not required.

............................................................................................................................

............................................................................................................................

............................................................................................................................ (3)

(iii) Suggest, with reasoning, whether a laboratory coat made from a polyester might be

damaged by a spillage on it of hot concentrated aqueous sodium hydroxide

solution.

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(iv) Give another type of reagent that could be used to make an ester from an alcohol.

............................................................................................................................ (1)

(Total 13 marks)

11. (a) Methane reacts with steam in a reversible reaction. In industry this reaction, carried out at

a pressure of 30 atm, is used to produce hydrogen for the manufacture of ammonia

CH4(g) + H2O(g) CO(g) + 3H2(g) H = +210 kJ mol–1

(i) Define the term partial pressure as applied to a gas mixture.

............................................................................................................................

............................................................................................................................ (1)

(ii) Write an expression for the equilibrium constant, Kp, for this reaction.

(1)

(iii) State and explain the effect of increasing the total pressure on the position of this

equilibrium;

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(b) State the effect on the value of Kp for this equilibrium of the following.

(i) Increasing the total pressure.

............................................................................................................................ (1)

(ii) Increasing the temperature.

............................................................................................................................ (1)

(iii) Adding a catalyst.

............................................................................................................................ (1)

(c) There is a theory that methane, CH4, constantly leaks from the earth‘s crust. This is not

noticeable on land but at the bottom of a cold sea, such as off the Canadian coast, the

methane is trapped in a solid cage of water molecules.

CH4(g) + 6H2O(s) [CH4(H2O)6](s)

methane hydrate

At –29 °C the equilibrium pressure of the methane is 101.3 kPa.

(i) Write an expression for Kp for this equilibrium.

(1)

(ii) Deduce the value of Kp at –29 °C, stating its units.

(1)

(iii) At 0 °C the equilibrium pressure of methane rises to 2600 kPa. What does this tell

you about the effect of temperature change on the position of equilibrium and

about the enthalpy change for this reaction?

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(iv) Some people have suggested collecting the methane hydrate from the bottom of the

sea and allowing it to warm up to 0 °C on board a ship. Comment on whether this

would be a useful method for collecting methane.

............................................................................................................................

............................................................................................................................

............................................................................................................................ (1)

(Total 12 marks)

12. Ethanoic acid, CH3COOH, is a weak acid which can be used, with its salts, to make buffer

solutions.

(a) Explain what is meant by the term weak acid.

....................................................................................................................................

.................................................................................................................................... (1)

(b) Explain what is meant by the term buffer solution.

....................................................................................................................................

.................................................................................................................................... (2)

(c) An aqueous solution of ethanoic acid of concentration 1.00 mol dm–3

has a pH of 2.8.

Sketch, with care, how the pH changes during the titration of 25.0 cm3 1.00 mol dm

–3

aqueous ethanoic acid with aqueous sodium hydroxide of the same concentration.

14

12

10

8

6

4

2

00 10 20 30 40 50

Volume of alkali added/cm

pH

3 (4)

(d) Indicate on your sketch the portion of the curve where the mixture is behaving as a buffer. (1)

(e) (i) Write an expression for the dissociation constant, Ka, for ethanoic acid.

(1)

(ii) Explain how the pKa of ethanoic could be found from the graph.

............................................................................................................................

............................................................................................................................ (2)

(Total 11 marks)

13. In an experiment to determine the rate of the reaction between persulphate ions and iodide ions

in aqueous solution

S2O –28 + 2I

– 2SO –2

4 + I2

the following data were obtained:

Concentration/mol dm

S O

0.100

0.200

0.200

I

0.100 0.36

0.100 0.72

0.200 1.44

2 82–

–3

–3 –1–

Initial rate/mol dm s

(a) (i) Deduce the order of reaction with respect to each of the reagents and hence write

the rate equation for the reaction.

............................................................................................................................

............................................................................................................................

............................................................................................................................ (3)

(ii) With reference to this reaction state what is meant by the overall order of a

reaction.

............................................................................................................................

............................................................................................................................ (1)

(iii) Calculate the rate constant including units.

(2)

(iv) Explain why the rate equation cannot be written directly from the stoichiometric

equation for the reaction.

............................................................................................................................

............................................................................................................................ (1)

(b) (i) Suggest a suitable experimental technique that would enable you to determine the

rate of the reaction given opposite.

............................................................................................................................

............................................................................................................................ (1)

(ii) Suggest a necessary condition that would help to ensure accurate results.

............................................................................................................................ (1)

(iii) Suggest one advantage or disadvantage of your chosen experimental method.

............................................................................................................................

............................................................................................................................ (1)

(Total 10 marks)

14. (a) The first stage in the manufacture of sulphuric acid is the Contact Process.

2SO2 + O2 2SO3

At 400 °C the equilibrium constant Kp = 3.00 × 104 atm

–1. A catalyst of vanadium(V)

oxide is used. In a particular equilibrium mixture at 400 °C the partial pressures of

sulphur dioxide and of oxygen were 0.100 atm and 0.500 atm respectively. Show that the

yield of SO3 is about 95% of the equilibrium mixture.

(5)

(b) (i) Pure sulphuric acid is a viscous liquid with a high boiling temperature of

338 °C. It has the structure:

O

S

OHOH

O

Suggest in terms of the intermolecular forces in sulphuric acid why it has such a

high boiling temperature. (3)

(ii) Sulphuric acid dissolves in water in a highly exothermic reaction

May her rest be long and placid,

She added water to the acid;

The other girl did what we taught her,

And added acid to the water.

Suggest why sulphuric acid must always be added to water to dilute it rather than

the other way round. (2)

(c) Sulphuric acid dissociates in water according to the equations:

H2SO4 + H2O H3O+ + HSO –

4

HSO –4 + H2O H3O

+ + SO

–24

The dissociation constant for the first dissociation is very large; that for the second is 0.01

mol dm–3

at 25 °C.

(i) Calculate the pH of an aqueous solution containing 0.200 mol dm–3

hydrogen ions. (1)

(ii) The pH of 0.100 mol dm–3

sulphuric acid is 0.98. Explain why this is so close to

the pH of 0.100 mol dm–3

HCl which is 1.0. (3)

(d) Sulphuric acid is used as the electrolyte in the lead-acid battery found in cars. The

electrodes are made from lead and from lead(IV) oxide. As the cell discharges, the lead

and the lead(IV) oxide are both converted to lead(II) sulphate, and the sulphuric acid

concentration falls.

(i) Use the information above to deduce the two half equations occurring in the lead

acid battery. (3)

(ii) Hence write an equation to represent the overall process taking place as the cell

discharges. (1)

(Total 18 marks)

15. (a) Define the following terms.

(i) pH ..................................................................................................................... (1)

(ii) Kw ......................................................................................................................

(1)

(b) Explain the meaning of the term strong, as applied to an acid or a base.

………………...……………….……………………………………………………..

………………...……………….…………………………………………………….. (1)

(c) Calculate the pH of the following solutions.

(i) HCl(aq) of concentration 0.200 mol dm–3

.

(1)

(ii) NaOH (aq) of concentration 0.800 mol dm–3

(Kw = – 1.00 × 10–14

mol2 dm

–6).

(2)

(d) HA is a weak acid with a dissociation constant Ka = 5.62 × 10–5

mol dm–3

.

(i) Write an expression for the dissociation constant, Ka, of HA.

(1)

(ii) Calculate the pH of a 0.400 mol dm–3

solution of HA.

(3)

(e) A buffer solution contains HA(aq) at a concentration of 0.300 mol dm–3

, and its sodium

salt, NaA, at a concentration of 0.600 mol dm–3

. Calculate the pH of this buffer solution.

(3)

(Total 13 marks)

16. Consider the following equation:

2SO2 + O2 2SO3

2.0 moles of SO2 and 1.0 mole of O2 were allowed to react in a vessel of volume 60 dm3.

At equilibrium 1.8 moles of SO3 had formed and the pressure in the flask was 2 atm.

(a) (i) Write the expression for Kc for this reaction between SO2 and O2.

(1)

(ii) Calculate the value of Kc, with units.

(3)

(b) The reaction between SO2 and O2 is exothermic. State the effect on the following, if the

experiment is repeated at a higher temperature:

(i) Kc ……………………………………………………………………………..

(1)

(ii) the equilibrium position .................................................................................... (1)

(c) State the effect of a catalyst on:

(i) Kc ……………………………………………………………………………..

(1)

(ii) the equilibrium position .................................................................................... (1)

(d) (i) Write the expression for Kp for the reaction between SO2 and O2.

(1)

(ii) Calculate the mole fractions of SO2, O2 and SO3 at equilibrium.

(2)

(iii) Calculate the partial pressures of SO2, O2 and SO3 at equilibrium.

(1)

(iv) Calculate the value of Kp, with units.

(2)

(Total 14 marks)

17. (a) (i) Explain what is meant by the following terms.

Rate of reaction ………………………………………………………………

………………...……………….………………….…………………………..

………………...……………….………………….…………………………..

Overall order of a reaction ................................................................................

………………...……………….………………….…………………………..

………………...……………….………………….………………………….. (2)

(ii) Explain why the order of reaction cannot be deduced from the stoichiometric

equation for a reaction.

………………...……………….………………….…………………………..

………………...……………….………………….…………………………..

………………...……………….………………….………………………….. (1)

(b) Substitution reactions of halogenoalkanes, can proceed via an SN1 or SN2 mechanism.

When 1-bromobutane, CH3CH2CH2CH2Br, 2-bromobutane, CH3CH2CHBrCH3, and

2-bromo-2-methylpropane, (CH3)3CBr, are reacted separately with aqueous sodium

hydroxide solution each gives the corresponding alcohol.

(i) Give the mechanism for the SN1 reaction between 2-bromobutane and

hydroxide ions.

(3)

(ii) Explain why the product mixture is not optically active.

………………...……………….………………….…………………………..

………………...……………….………………….…………………………..

………………...……………….………………….………………………….. (2)

(iii) In an experiment designed to find the mechanism of the reaction between 2-bromo-

2-methylpropane and hydroxide ions the following data were obtained at constant

temperature.

Initial concentration of

2-bromo-2-methylpropane

/mol dm–3

Initial concentration of

OH– / mol dm

–3

Initial rate of reaction

/mol dm–3

s–1

0.10 0.10 1.2 × 10–2

0.20 0.10 2.4 × 10–2

0.30 0.20 3.6 × 10–2

Use the data to deduce the rate equation for the reaction of 2-bromo-2-

methylpropane with sodium hydroxide solution.

………………...……………….………………….…………………………..

………………...……………….………………….…………………………..

………………...……………….………………….………………………….. (3)

(c) Suggest, in outline, a method you could use to follow the progress of the reaction between

a bromoalkane and aqueous sodium hydroxide.

………………………...……………….………………….…………………………..

………………………...……………….………………….…………………………..

………………………...……………….………………….…………………………..

………………………...……………….………………….…………………………..

………………………...……………….………………….…………………………..

………………………...……………….………………….………………………….. (3)

(Total 14 marks)

18. The pain-relieving drug ibuprofen has the formula

CC CH

CHCH

CO HCH

HH

33

2

23

(a) A molecule of this compound is chiral. Explain, with the aid of diagrams, how two

optical isomers result from chiral a centre. Identify the chiral centre in such a molecule

and explain how these isomers could be distinguished from each other. (4)

(b) Compounds A and B, shown below, are used as intermediates in the manufacture of

ibuprofen.

C CC CCH CH

CH CHCH CH

OHCH CH

O HH H

3 33 3

2 2

3 3

A B

(i) Suggest how infra-red spectroscopy could be used to identify an impurity in a

sample of ibuprofen which is known to be one of these two compounds.

A table of infra-red absorbencies is given below.

Bond Assignment Wavenumbers/cm–1

C-H alkanes

alkenes, arenes

2850 - 2950

3000 - 3100

benzene ring arenes 1450 - 1650

C=O aldehydes, ketones, esters,

carboxylic acids

1680 - 1750

O-H free

hydrogen bonded in alcohols or phenols

hydrogen bonded in carboxylic acids

3580 - 3670

3230 - 3550

2500 - 3300

(3)

(ii) Suggest a simple chemical test which would distinguish between A and B. (2)

(iii) Treatment of either A or B if heated with a mixture of aqueous sodium hydroxide

and potassium manganate(VII) solution would produce the same compound.

Suggest the structure of this compound. (2)

(c) A tablet of ibuprofen contains a very small quantity of the drug and the remainder of the

tablet material is unreactive.

In an analysis 50 tablets were reacted with 100.0 cm3 of 1.00 mol dm

–3 aqueous sodium

hydroxide, an excess. The ibuprofen reacted as a weak acid. When the reaction was

complete, the remaining aqueous sodium hydroxide was titrated with 2.00 mol dm–3

hydrochloric acid. 25.75 cm3 of the acid were required for neutralisation.

(i) Calculate the mass, in mg, of ibuprofen in each tablet.

(Mr for ibuprofen = 206)

(5)

(ii) Calculate the number of molecules of ibuprofen that this tablet represents.

(Avogadro constant h = 6.023 × 1023

mol–1

) (2)

(d) Ibuprofen is almost insoluble in aqueous solutions at pH 3 but if the pH is raised to 8 then

the ibuprofen becomes reasonably soluble. Account for these observations. (4)

(e) Under the appropriate conditions ibuprofen reacts with ethanol to produce a substance

with a characteristic odour. Identify the functional group in ibuprofen that would react

with the ethanol. Suggest the conditions needed for the reaction to take place and identify

the product. (3)

(Total 25 marks)

19. Manganate(VII) ions react with ethanedioate ions in acidic solution.

2MnO4–(aq) + 16H

+(aq) + 5C2O4

2–(aq) 2Mn

2+(aq) + 8H2O(l) + 10CO2(g)

(a) In a particular experiment 200 cm3 of aqueous potassium manganate(VII), KMnO4,

of concentration 0.0500 mol dm–3

were mixed with 50.0 cm3 of ethanedioic acid,

HOOCCOOH, of concentration 0.500 mol dm–3

, and 80 cm3 of 1.0 mol dm

–3 sulphuric

acid.

(i) Show by calculation that the starting concentration of the manganate(VII) ions was

3.03 × 10–2

mol dm–3

. (1)

(ii) The concentration of the manganate(VII) ions was determined over a period

of time.

Time / s Concentration of manganate(VII) ions/ mol dm–

3

0 3.03 × 10–2

400 2.98 × 10–2

800 2.86 × 10–2

1200 2.75 × 10–2

1600 1.90 × 10–2

2000 7.50 × 10–3

2400 2.50 × 10–3

Plot a graph of the concentration of manganate(VII) ions against time and from it

determine the initial rate of the reaction and the rate at 1600 s. (5)

(b) A second experiment was set up involving the same chemicals in the same concentrations

as in experiment 1 but this time some solid manganese(II) sulphate was dissolved in the

ethanedioic acid before the potassium manganate (VII) solution was poured in. The plot

of the concentration of manganate(VII) ions against time is given below:

3.5 × 10

3.0 × 10

2.5 × 10

2.0 × 10

1.5 × 10

1.0 × 10

5.0 × 10

0

–2

–2

–2

–2

–2

–2

–3

0 400 800 1200 1600 2000 2400

time / s

–3

con

cen

trati

on

/m

ol

dm

(i) Determine the order of the reaction with respect to manganate(VII) ions by

considering the time taken for the concentration to fall by half, using the

concentrations at 0, 800 and 1600 s. (3)

(ii) Compare this graph with the one you plotted in (a) (ii) and give two pieces of

evidence that manganese(II) sulphate is a catalyst for this reaction. (2)

(c) (i) Carrying out a flame test on potassium manganate(VII) gives a lilac flame.

What does this show? (1)

(ii) Describe how aqueous sodium hydroxide solution could be used to show that

manganese(II) ions had been produced in the reaction between manganate (VII)

ions and ethanedioate ions in acidic solution. (2)

(Total 14 marks)

20. Thermochemical data, at 298 K, for the equilibrium between zinc carbonate, zinc oxide and

carbon dioxide is shown below.

ZnCO3(s) ZnO(s) + CO2(g) ∆Hο = +71.0 kJ mol

–1

Sο[ZnO(s)] = +43.6 J mol

–1 K

–1

Sο[ZnCO3(s)] = +82.4 J mol

–1 K

–1

Sο[CO2(g)] = +213.6 J mol

–1 K

–1

(a) (i) Suggest reasons for the differences between the three standard entropies.

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(ii) Calculate the entropy change for the system, ∆Sο

system, for this reaction. Include the

sign and units in your answer.

(2)

(b) Calculate the entropy change for the surroundings, ∆Sοsurroundings, at 298 K, showing your

method clearly.

(2)

(c) (i) Calculate the total entropy change for this reaction, ∆Sοtotal, at 298 K.

(1)

(ii) What does the result of your calculation in (c)(i) indicate about the natural

direction of this reaction at 298 K?

Justify your answer.

............................................................................................................................

............................................................................................................................ (1)

(d) (i) Write an expression for the equilibrium constant, Kp, for this reaction.

(1)

(ii) State how you would alter ONE condition to increase the yield of carbon dioxide

from this equilibrium reaction.

Justify your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 11 marks)

21. Hydrogen peroxide decomposes to form water and oxygen.

H2O2(aq) H2O(l) + 21 O2(g)

(a) Suggest a method for following the rate of this reaction.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(b) The reaction is first order with respect to hydrogen peroxide.

(i) Explain what is meant by the term first order.

............................................................................................................................

............................................................................................................................ (1)

(ii) The overall order of the reaction is one. Give the rate equation for the reaction.

Rate =

(1)

(iii) How would you use a graph of hydrogen peroxide concentration against time to

show that the reaction is first order?

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(c) The data in the table show the effect of temperature on the rate of this reaction.

T

/K

Rate

/ mol dm–3

s–1

1/T

/K–1

ln(rate)

293 1.6 ×10–6

3.41 ×10–3

–13.3

302 4.2 ×10–6

3.31 ×10–3

–12.4

314 14.4 ×10–6

3.19 ×10–3

–11.1

323 33.8 ×10–6

3.10 ×10–3

–10.3

(i) On the axes below, sketch graphs for two temperatures, T1 and T2, where T2 is

greater than T1, and use them to explain why increasing temperature has a dramatic

effect on the rate of this reaction.

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................ (4)

(ii) Plot a graph of ln(rate), on the vertical axis, against 1/temperature, on the

horizontal axis, on the grid below.

(3)

(iii) Use your graph and the equation below to calculate the activation energy, EA, for

this reaction.

ln(rate) = constant R

AE (1/T) where R = 8.31 J K

–1 mol

–1

You should include the sign and units with your answer which should be given to

two significant figures.

(3)

(Total 16 marks)

22. (a) Define the term partial pressure.

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (1)

(b) If phosphorus pentachloride is heated in a sealed tube the following equilibrium is set up

PCl5(g) PCl3(g) + Cl2(g)

(i) Write an expression for the equilibrium constant, Kp, for the above reaction.

(1)

(ii) At a given temperature T a sample of phosphorus pentachloride is 40.0%

dissociated, the total equilibrium pressure being 2.00 atm. Calculate the partial

pressures of each of the components of the equilibrium mixture, to three significant

figures. Hence calculate the value of Kp under these conditions.

(5)

(c) At a higher temperature, T + t, the equilibrium mixture in (b) contains a greater

proportion of phosphorus trichloride and chlorine.

(i) State, with a reason, whether the dissociation of phosphorus pentachloride is

exothermic or endothermic.

......................................................................................................................

......................................................................................................................

...................................................................................................................... (2)

(ii) How does Kp change when the temperature is increased?

...................................................................................................................... (1)

(d) If calcium carbonate is heated in a sealed vessel in the absence of air the following

equilibrium is set up:

CaCO3(s) CaO(s) + CO2(g)

(i) Write the expression for Kp for this equilibrium.

...................................................................................................................... (1)

(ii) At 1030 °C the total pressure in the vessel is 16 atm. What is the value of Kp?

...................................................................................................................... (1)

(Total 12 marks)

23. Propanoic acid is a weak acid which dissociates according to

CH3CH2COOH(aq) + H2O(l) CH3CH2COO–(aq) + H3O

+(aq)

(a) (i) Indicate, in the space provided below the equation, the two acid/base conjugate

pairs. (2)

(ii) Write the expression for the acid dissociation constant, Ka, for propanoic acid.

(1)

(iii) Calculate the pH of a 0.100 mol dm–3

solution of propanoic acid, for which

Ka = 1.3 × 10–5

mol dm–3

.

(3)

(iv) Calculate the concentration of hydroxide ions, OH–, in this same solution of

propanoic acid. Kw = 1.00 × 10–14

mol2 dm

–6 at the temperature of the solution.

(3)

(b) If sodium propanoate is dissolved in water, the pH of the resulting solution is not 7, but is

near to 8. By writing the equation for the reaction occurring suggest why this is so.

................................................................................................................................

................................................................................................................................

................................................................................................................................ (2)

(c) A mixture of sodium propanoate and propanoic acid behaves as a buffer solution.

(i) What is meant by a buffer solution?

......................................................................................................................

......................................................................................................................

...................................................................................................................... (2)

(ii) Calculate the pH of a buffer solution that is made by mixing equal volumes of

0.0500 mol dm–3

propanoic acid and 0.100 mol dm–3

sodium propanoate.

(3)

(Total 16 marks)

24. (a) In a rate of reaction experiment between two substances, A and B, the overall order of the

reaction was found to be 2. Write three possible rate equations for such a second order

reaction between A and B.

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (3)

(b) At a certain temperature the rate of reaction between nitrogen monoxide, NO, and

hydrogen, H2, was investigated. The following data were obtained.

[NO]/mol dm–3

[H2]/mol dm–3

Rate/mol dm–3

s–1

1.0 1.0 0.02

1.0 3.0 0.06

3.0 1.0 0.18

(i) Use the data above to deduce the rate equation for this reaction.

(3)

(ii) Use your answer to (b)(i) above to calculate the value of the rate constant, with

units.

(2)

(c) The investigation described in part (b), above, was repeated, but at a higher temperature,

and the rate of the reactions increased. Explain, in terms of particles, why an increase in

temperature increases the rate of a reaction.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (3)

(d) State the effect of an increase in temperature on the value of the rate constant, k.

............................................................................................................................... (1)

(e) Explain the effect of a catalyst on the rate of a reaction.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (3)

(Total 15 marks)

25. (a) The equation below shows the reaction which occurs when ammonia is dissolved in

water.

NH3(g) + H2O(1) NH 4 (aq) + OH

–(aq)

(i) Explain why water is classified as an acid in this reaction.

..........................................................................................................................

.......................................................................................................................... (1)

(ii) The ammonia is acting as a weak base in this reaction.

What is the difference between a weak base and a strong base?

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (1)

(b) Ammonia reacts with oxygen to form the gases nitrogen(II) oxide and steam.

(i) Complete the Hess cycle below so that ΔHreaction can be calculated using standard

enthalpy changes of formation. Include state symbols.

(2)

(ii) Calculate ΔHreaction for this reaction using the following data.

ΔHf [NH3(g)] = – 46.1 kJ mol–1

ΔHf [NO(g)] = + 90.2 kJ mol–1

ΔHf [H2O(g)] = – 241.8 kJ mol–1

Include a sign and units in your answer and give your answer to three significant

figures.

(3)

(Total 7 marks)

26. The reaction between solid barium hydroxide and solid ammonium chloride can be

represented by the equation below.

Ba(OH)2(s) + 2NH4Cl(s) BaCl2(s) + 2NH3(g) + 2H2O(l) ΔHο = +51.1 kJ mol

–1

The standard entropies, at 298 K, for the reactants and products are:

Sο[Ba(OH)2(s)] = + 99.7 J mol

–1K

–1

Sο[NH4Cl(s)] = + 94.6 J mol

–1K

–1

Sο[BaCl2(s)] = + 123.7 J mol

–1K

–1

Sο[NH3(g)] = + 192.3 J mol

–1K

–1

Sο[H2O(l)] = + 69.9 J mol

–1K

–1

(a) Why is the standard entropy of ammonia more positive than the standard entropy of

barium chloride?

....................................................................................................................................

.................................................................................................................................... (1)

(b) Use the values given to calculate the standard entropy change, ΔSοsystem, for this reaction.

Include the sign and units in your answer.

(2)

(c) Calculate the standard entropy change of the surroundings, ΔSοsurroundings, at 298 K for

this reaction.

(2)

(d) Use your answers to (b) and (c) to show that this reaction is feasible at 298 K.

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (1)

(e) Calculate the minimum temperature, in kelvin, at which the reaction is spontaneous.

(2)

(Total 8 marks)

27. This question is about propanal, CH3CH2CHO, propanone, CH3COCH3, and propanoic acid,

CH3CH2CO2H.

(a) Explain why all three compounds are soluble in water.

....................................................................................................................................

.................................................................................................................................... (1)

(b) Propanal and propanone contain the carbonyl group.

State a chemical test for the presence of this group. Give the result of a positive test.

Test ...........................................................................................................................

Result ........................................................................................................................ (2)

(c) Propanal can be distinguished from propanone by its oxidation to propanoic acid.

(i) Name an oxidising agent you would use.

.........................................................................................................................

......................................................................................................................... (1)

(ii) State the colour change you would observe during the oxidation.

From ...................................................... to ...................................................... (1)

(iii) State how propanone can be distinguished from propanal using infra-red spectra.

You are not expected to give actual absorption values, but you should indicate the

bonds in the molecules which would give rise to the distinguishing absorptions.

.........................................................................................................................

......................................................................................................................... (1)

(d) A useful test for carboxylic acids is that they will neutralise sodium carbonate solution.

Write a balanced equation, including state symbols, for the neutralisation of sodium

carbonate solution by propanoic acid.

(2)

(e) Give the names of TWO other inorganic chemicals that could be used to make sodium

propanoate from propanoic acid.

....................................................................................................................................

.................................................................................................................................... (2)

(Total 10 marks)

28. A saturated solution of calcium hydroxide, Ca(OH)2(aq), has a pH of 9.6.

(a) Write an expression linking hydrogen ion concentration and pH. Use this to calculate the

concentration of hydrogen ions in this solution.

(3)

(b) (i) The ionisation constant for water, Kw = 1.0 × 10–14

mol2 dm

–6.

Write the expression for Kw.

Kw =

(1)

(ii) Calculate the concentration of hydroxide ions in the saturated solution of calcium

hydroxide.

(1)

(iii) Calculate the concentration of calcium hydroxide in the saturated solution.

(1)

(iv) Calculate the solubility of calcium hydroxide in g dm–3

.

Give your answer to three significant figures.

(1)

(v) Suggest why your calculated value may differ significantly from the value in

chemistry reference books.

.........................................................................................................................

......................................................................................................................... (1)

(c) An alternative method for finding the solubility of calcium hydroxide is to titrate 100 cm3

of the saturated solution with hydrochloric acid of concentration 0.00100 mol dm–3

.

Ca(OH)2 (aq) + 2HCl (aq) CaCl2 (aq) + 2H2O (l)

(i) Calculate the pH of the hydrochloric acid.

(1)

(ii) Use your answer to (b)(iii) and the information above to calculate the volume of

hydrochloric acid needed to neutralise 100 cm3 of the saturated calcium

hydroxide solution.

(3)

(iii) Sketch the titration curve for this reaction.

(2)

(iv) Suggest why phenolphthalein is not a suitable indicator for this reaction.

..........................................................................................................................

.......................................................................................................................... (1)

(Total 15 marks)

29. This question is about the hydrolysis of 2-bromo-2-methylbutane.

C5H11Br + H2O C5H11OH + HBr

(a) 15 cm3 of water was mixed with 15 cm

3 of ethanol. 1.0 cm

3 of 2-bromo-2-methylbutane

was added to this mixture. The conductivity of this mixture was measured and rose from

0 to 200 microsiemens in 600 s.

The experiment was repeated using equal volumes of water and ethanol, with 2.0 cm3 of

2-bromo-2-methylbutane in the 31 cm3 of mixture. The conductivity of the mixture rose

from 0 to 400 microsiemens in 600 s.

(i) Explain why the conductivity of the mixture increases during these reactions.

..........................................................................................................................

.......................................................................................................................... (1)

(ii) Why was an ethanol/water mixture used for this reaction rather than water on its

own?

..........................................................................................................................

.......................................................................................................................... (1)

(iii) What is the effect on the rate of the reaction of doubling the concentration of

2-bromo-2-methylbutane?

.......................................................................................................................... (1)

(iv) Deduce the order of the reaction with respect to 2-bromo-2-methylbutane.

.......................................................................................................................... (1)

(v) Explain why this is the order of reaction with respect to 2-bromo-2-methylbutane

and not the overall order of the reaction.

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (1)

(b) The table below shows the results from another experiment where a solution of

2-bromo-2-methylbutane is reacted with varying concentrations of hydroxide ions.

A few drops of an acid-alkali indicator are added to the mixture and the time for the

indicator to change to the acidic colour is measured.

[C5H11Br]

/10–2

mol dm–3

[OH–]

/10–3

mol dm–3

Time

/s

1.5 0.75 5

1.5 1.50 9

1.5 2.25 14

(i) Calculate the rate of the reaction, in mol dm–3

s–1

, for each concentration of

hydroxide ions.

(2)

(ii) What effect does doubling the concentration of hydroxide ions have on the rate of

the reaction?

.......................................................................................................................... (1)

(iii) What is the order of the reaction with respect to the hydroxide ions?

.......................................................................................................................... (1)

(c) When 2-bromo-2-methylbutane reacts with water, or hydroxide ions, the mechanism for

the reaction is the same.

(i) Use your answers to (a)(iv) and (b)(iii) to write the rate equation for the reaction

with hydroxide ions.

Rate =

(1)

(ii) Write a mechanism for the reaction which is consistent with your rate equation.

(2)

(Total 12 marks)

30. (a) Ammonia reacts with water as below:

NH3(aq) + H2O(l) NH4+(aq) + OH

–(aq)

A 0.100 mol dm–3

solution of ammonia has a pH of 11.13.

(i) Identify the Bronsted–Lowry acid/base conjugate pairs in the equation. Clearly

label which are acids and which are bases.

.....................................................................................................................................

..................................................................................................................................... (2)

(ii) Draw, on the axes below, a graph to show how the pH of the solution varies as

40 cm3 of 0.100 mol dm

–3 hydrochloric acid (a strong acid) is added slowly to

20 cm3 of the ammonia solution.

14

12

10

8

6

4

2

010 20 30 40 50

Volume of HCl solution / cm 3

pH

(4)

(iii) Select, from the following list, the indicator which would be the most suitable for

this titration. Give a reason for your choice.

Indicator pKind Range

methyl red 5.1 4.2–6.3

bromothymol blue 7.0 6.0–7.6

phenolphthalein 9.3 8.2–10.0

Indicator: ....................................................................................................................

Reason: ......................................................................................................................

..................................................................................................................................... (2)

(b) Nitrous acid, HNO2, is a weak acid with an acid dissociation constant

Ka = 4.70 × 10–4

mol dm–3

at 4 °C.

HNO2(aq) + H2O(l) H3O+(aq) + NO2

–(aq)

(i) Write the expression for Ka.

(1)

(ii) Calculate the pH of a 0.120 mol dm–3

solution of nitrous acid.

(3)

(iii) Calculate the pH of a buffer solution made by adding 1.38 g of sodium nitrite,

NaNO2, to 100 cm3 of the 0.120 mol dm

–3 solution of nitrous acid

(Ka = 4.70 × 10–4

mol dm–3

).

(4)

(iv) Suggest why a mixture of nitrous acid and sodium nitrite can act as a buffer

solution whereas a solution of sodium nitrite on its own does not.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 18 marks)

31. In an acidic solution, propanone reacts with iodine as follows:

CH3COCH3 + I2 CH3COCH2I + HI

The rate of this reaction can be followed by removing portions of the reaction mixture at known

times, adding them to a solution of sodium hydrogen carbonate to stop the reaction and then

titrating the mixture with standard sodium thiosulphate solution.

(a) (i) Write the ionic equation for the reaction of thiosulphate ions with iodine in

aqueous solution.

..................................................................................................................................... (2)

(ii) State which indicator is used in this titration, and describe what you would see at

the end point.

.....................................................................................................................................

..................................................................................................................................... (2)

(b) Use the following data to deduce the rate equation for the reaction of propanone with

iodine in acidic solution, given that the order with respect to [H+] is one.

[CH3COCH3]

/mol dm–3

[I2]

/mol dm–3

Initial rate

/mol dm–3

s–1

1.0 0.10 3.2 × 10–3

1.0 0.20 3.2 × 10–3

2.0 0.10 6.4 × 10–3

(3)

(c) What is meant by:

(i) order of reaction with respect to a particular reactant

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(ii) overall order of reaction.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(d) What does the rate equation in (b) tell you about the involvement of iodine in the rate-

determining step, and hence about the least number of steps in the reaction?

...............................................................................................................................................

...............................................................................................................................................

............................................................................................................................................... (2)

(e) Sodium hydroxide cannot be used to stop the reaction, because very alkaline conditions

cause another reaction to occur between propanone and iodine.

Write the equation for this reaction.

............................................................................................................................................... (3)

(Total 14 marks)

32. This question is about the kinetics of the reaction in which ammonium cyanate, NH4CNO, turns

into urea, NH2CONH2, in aqueous solution.

NH4CNO(aq) ΝΗ2CONH2(aq)

The table below shows the mass of urea, mt, which formed at different times in a solution of

ammonium cyanate of known starting concentration.

When the reaction stopped the mass of urea, mfinal, was 20.3 g.

Time / min Mass of urea, mt /g mfinal – mt/g

0 0 20.3

25 12.5 7.8

50 15.7 4.6

75 17.1 3.2

100 17.5 2.8

150 18.7 1.6

200 19.1

300 20.0

(a) Complete the final column of the table. (1)

(b) Plot a graph of mfinal – mt (on the vertical axis) against time (on the horizontal axis).

(2)

(c) The graph can be used to work out a rate equation for the reaction.

What term in the rate equation for the reaction is proportional to mfinal – mt?

………......................................................................................................................... (1)

(d) (i) Show THREE successive half-life measurements on your graph, and give their

values.

1. ........................................................... 2. ...........................................................

3. ........................................................... (2)

(ii) Use the half-lives to decide whether the reaction is zero order, first order or second

order. Explain how you decided the order.

Order of reaction ..............................................................................................

Explanation .......................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(iii) Suggest a possible rate equation for the reaction.

.......................................................................................................................... (1)

(e) A student thought that water might take part in the rate-determining step of the reaction.

(i) What is meant by the rate-determining step?

.......................................................................................................................... (1)

(ii) The solution of ammonium cyanate used in the experiment initially contained 0.35

moles of ammonium cyanate in approximately 1 dm3 (55.5 moles) of water.

Is the order you calculated in (d)(ii) an order with respect to ammonium cyanate, or

could it include the water as well? Explain your answer.

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(Total 12 marks)

33. When dinitrogen tetroxide, N2O4, dissociates, the following equilibrium is established.

N2O4(g) 2NO2(g)

(a) State a property which could be measured to follow the progress of this reversible

reaction.

.................................................................................................................................... (1)

(b) Write an expression for the equilibrium constant, Kc, for this reaction.

(1)

(c) When a sample of 0.0370 moles of gaseous dinitrogen tetroxide is allowed to dissociate at

25 °C in a container of volume 1 dm3, 0.0310 moles of N2O4(g) remain in the equilibrium

mixture.

Complete the table below, and use the data to calculate Kc for the reaction. Include a unit

in your answer.

N2O4 NO2

Number of moles at start 0.0370 0

Number of moles in 1 dm3

at equilibrium 0.0310

Kc calculation:

(3)

(d) The reaction was repeated at a higher pressure, maintaining the temperature at 25 °C.

(i) How does this increase in pressure affect the amount of nitrogen dioxide, NO2(g),

in the equilibrium mixture?

.......................................................................................................................... (1)

(ii) How does this increase in pressure affect the value of Kc?

.......................................................................................................................... (1)

(e) The reaction was repeated at the original pressure, but the temperature was increased to

75 °C. The value of Kc was approximately twenty times greater.

How does this information show that the reaction is endothermic?

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (1)

(f) Predict the sign of ΔSsystem for the reaction, giving a reason for your answer.

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (2)

(g) Write the equation for the relationship between ΔSsurroundings and ΔH for the reaction.

(1)

(h) The magnitude of ΔSsystem for the reaction is greater than the magnitude of ΔSsurroundings.

Explain why this must be the case.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (2)

(Total 13 marks)

34. This question is about the chemistry of benzoic acid, C6H5CO2H.

The scheme below shows some reactions of benzoic acid.

(a) (i) What type of reaction is Reaction 1?

.......................................................................................................................... (1)

(ii) Suggest a reagent which could be used to convert the —CO2H group to the

—CH2OH group without affecting the benzene ring.

.......................................................................................................................... (1)

(iii) Suggest why the reactant you chose in (ii) does not attack the benzene ring.

..........................................................................................................................

.......................................................................................................................... (1)

(b) (i) Suggest a structural formula for A.

(1)

(ii) Name the type and mechanism of this reaction.

Type ................................................... Mechanism .................................................. (2)

(c) (i) Give the structural formula and state the name for B.

Name ................................................................................................................ (2)

(ii) Give ONE use for the class of compounds to which B belongs.

.......................................................................................................................... (1)

(d) (i) Give the name for C6H5COCl.

.......................................................................................................................... (1)

(ii) C6H5COCl reacts more readily than benzoic acid with ethanol, also forming B as

the product. Explain this difference in reactivity.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

.......................................................................................................................... (2)

(e) Hydrogen can add to the benzene ring in benzoic acid, but only under conditions of high

temperature and pressure in the presence of a catalyst. Explain why these severe

conditions are necessary for this addition reaction to occur.

....................................................................................................................................

.................................................................................................................................... (2)

(Total 14 marks)

35. (a) Benzoic acid is a weak acid. What is meant by a weak acid?

....................................................................................................................................

.................................................................................................................................... (1)

(b) Write an expression for the acid dissociation constant, Ka, for benzoic acid.

(1)

(c) Ka for benzoic acid has value 6.3 × 10–5

mol dm–3

. Use this data to calculate the pH of a

solution of benzoic acid of concentration 0.050 mol dm–3

.

(3)

(d) In a titration, 40.0 cm3 of 0.050 mol dm

–3 sodium hydroxide was added from a burette to

20.0 cm3 of 0.050 mol dm

–3 benzoic acid. Sketch a curve on the grid below to show how

the pH of the solution would change as the sodium hydroxide was added. Detailed

calculations are not required.

(3)

(e) Name a suitable indicator to detect the end-point of this titration.

.................................................................................................................................... (1)

(f) A mixture of benzoic acid and sodium benzoate can act as a buffer solution.

In what proportion must solutions of benzoic acid and sodium benzoate, of the same

concentration, be mixed to produce a buffer solution of pH 4.5?

You may use the equation pH = –log Ka –log [base]

[acid].

Ka for benzoic acid has value 6.3 × 10–5

mol dm–3

.

(2)

(g) Suggest a salt which would make a buffer solution with pH greater than 7 when mixed

with aqueous ammonia.

.................................................................................................................................... (1)

(Total 12 marks)

36. (a) (i) Use an equation to define the term pH.

..................................................................................................................................... (1)

(ii) Explain how some solutions can have a negative pH.

.....................................................................................................................................

..................................................................................................................................... (1)

(b) The concentration of propanoic acid can be found by titrating a sample with standard

sodium hydroxide solution.

(i) Calculate the pH of 0.100 mol dm–3

propanoic acid at 25 C; the value of the

dissociation constant for the acid, Ka, is 1.30 × 10–5

mol dm–3

.

(3)

(ii) Sketch with reasonable accuracy the titration curve that you would expect if

25.0 cm3 of 0.100 mol dm

–3 propanoic acid were to be titrated with 0.100 mol dm

–3

sodium hydroxide solution.

14

12

10

8

6

4

2

010 20 30 40 50

Volume of 0.100 mol dm–3 sodium hydroxide solution/cm3

(iii) What is the significance of the pH of the mixture when 12.5 cm3 of sodium

hydroxide had been added to the propanoic acid?

..................................................................................................................................... (1)

(Total 10 marks)

37. Alanine, 2-aminopropanoic acid, is the simplest chiral amino acid found in nature and is

optically active.

H

C C

O

O H

H N2

CH3

(a) (i) Explain the meaning of the term chiral.

.....................................................................................................................................

..................................................................................................................................... (1)

(ii) How is optical activity detected experimentally?

.....................................................................................................................................

..................................................................................................................................... (2)

(iii) If alanine is made from propanoic acid the product mixture does not show optical

activity. Explain why this is so.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(b) Alanine reacts with both acids and bases. Give the structural formulae of the compounds

you would expect if alanine reacts with

hydrochloric acid

sodium hydroxide

(2)

(c) Alanine has a high melting temperature of 300 °C, much higher than would be expected

for the structure given at the start of the question.

Draw the structure that is actually present in the solid, and explain why the melting

temperature is so high.

............................................................................................................................................

...........................................................................................................................................

............................................................................................................................................ (2)

(d) Polyamides are made from a diacid dichloride and a diamine; they are condensation

polymers.

(i) Explain the term condensation polymer.

.....................................................................................................................................

..................................................................................................................................... (1)

(ii) Suggest the structural formula of a diacid dichloride and a diamine that could be

reacted to form a polyamide.

(2)

(iii) Draw sufficient of the polymer chain that would result from the reaction of the

compounds in (ii) to make the structure of the polymer clear.

(2)

(iv) Alanine could be converted to CH3CH(NH2)COCl which on its own could

polymerise to a polyamide. Draw the structure of the polymer chain showing three

alanine repeating units and all the bonds in the amide links.

(2)

(Total 16 marks)

38. This question concerns the equilibrium

2NO(g) N2(g) + O2(g) H = –180 kJ mol–1

(a) Define the term partial pressure.

............................................................................................................................................

............................................................................................................................................ (1)

(b) (i) Write the expression for Kp for the above reaction.

(1)

(ii) At 1600 C and 1.5 atm pressure NO is 99 % dissociated at equilibrium. Calculate

the value of Kp under these conditions.

(4)

(c) State and explain the effect on Kp and hence on the position of equilibrium of decreasing

the temperature at constant pressure.

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................

............................................................................................................................................ (3)

(d) The reaction

Ni(s) + 4CO(g) Ni(CO)4(g)

is used to purify nickel.

(i) Write the expression for Kp for this system.

(1)

(ii) In order to achieve a high equilibrium yield of Ni(CO)4 should a low or a high

partial pressure of carbon monoxide be used? Explain your answer in terms of Kp.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 12 marks)

39. (a) The ester methyl ethanoate reacts with water as follows:

CH3COOCH3 + H2O CH3COOH + CH3OH

An experiment to investigate the kinetics of this hydrolysis showed that the concentration

of methyl ethanoate varied as shown in the graph below.

The water in this reaction is not only a reagent but is also the solvent and is therefore in

large excess.

00

0.05

0.10

0.20

0.25

0.30

0.35

0.5 1.0 1.5 2.0 2.5 3.0

[ester] / mol dm

Time / hr

–3

(i) Show, under these conditions, that the reaction is first order in methyl ethanoate.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(ii) Explain with a reason whether or not the overall order of reaction must also be one.

.....................................................................................................................................

..................................................................................................................................... (1)

(iii) Assuming the reaction is first order, use the graph to calculate the rate constant, k.

Include the units in your answer.

(3)

(iv) Suggest a method by which the progress of the reaction could be followed.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(b) The Arrhenius equation

ln k = ln A – Ea/RT

relates the rate constant k to the activation energy Ea for a reaction. A is a constant, R is

the gas constant.

(i) Comment on the relative values of the rate constant k at a given arbitrary

temperature T for two reactions, one of which has an activation energy of about

180 kJ mol–1

, the other of which has an activation energy of about 50 kJ mol–1

. No

calculation is expected.

.....................................................................................................................................

..................................................................................................................................... (1)

(ii) Suppose that these two different values of activation energy were for the same

overall reaction at the same temperature. Suggest a way in which the conditions

are different for the two reactions.

.....................................................................................................................................

..................................................................................................................................... (1)

(Total 11 marks)

40. Butan-1-ol, a primary alcohol, can be oxidised to form the aldehyde, butanal.

(a) Give the name or formula of an oxidising agent used in this reaction and of the other

reagent required.

Oxidising Agent

.....................................................................................................................................

Other Reagent

..................................................................................................................................... (2)

(b) A possible by-product of this reaction is butanoic acid, CH3CH2CH2CO2H, which is

classified as a weak acid.

Explain what is meant by a weak acid.

Acid ............................................................................................................................

.....................................................................................................................................

Weak ...........................................................................................................................

..................................................................................................................................... (2)

(Total 4 marks)

41. X and Y are isomers with the molecular formula C7H6O2.

(a) Complete the table with the observations you would make when separate samples of X

and Y are warmed gently in test-tubes with the following solutions.

Solution Observation with X Observation with Y

sodium carbonate

Brady‘s reagent

(2,4-dinitrophenylhydrazine)

potassium dichromate(VI) +

sulphuric acid

(6)

(b) Both X and Y can take part in reactions in which esters are formed.

(i) Complete the structural formula of the ester which forms when X reacts with

methanol.

(1)

(ii) Y reacts with ethanoyl chloride to form an ester.

Draw the displayed formula of ethanoyl chloride.

(1)

(iii) Complete the displayed formula of the ester which forms when Y reacts with

ethanoyl chloride.

(2)

(iv) When X forms an ester with methanol, a catalyst is needed for the reaction to

proceed at a reasonable speed when heated gently.

Name a suitable catalyst for the esterification reaction.

........................................................................................................................... (1)

(v) Explain why ethanoyl chloride is reactive enough to form an ester with Y at a

reasonable speed without a catalyst and without heating.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(c) The benzene ring in Y reacts readily with bromine in a substitution reaction.

(i) Name the type of reagent which attacks a benzene ring in substitution reactions.

........................................................................................................................... (1)

(ii) Give the formula of the species which attacks the benzene ring when it reacts with

bromine in a substitution reaction.

............................................................................................................................. (1)

(iii) Suggest a structural formula for an organic product of the reaction of bromine with

Y.

(1)

(iv) Y reacts with bromine more readily than benzene does. Suggest a reason for this.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(Total 17 marks)

42. 2-bromo-2-methylpropane reacts with aqueous sodium hydroxide as shown in the equation

below.

(CH3)3CBr + NaOH (CH3)3COH + NaBr

A series of experiments was carried out to investigate the kinetics of this reaction.

Initial concentration of

(CH3)3CBr

/mol dm3

Initial concentration of

NaOH

/mol dm3

Initial rate of reaction

/mol dm3

s1

5.0 × 104

2.0 × 102

1.5 × 104

1.5 × 103

2.0 × 102

4.5 × 104

1.5 × 103

4.0 × 102

4.5 × 104

(a) (i) Give the order of the reaction with respect to

2-bromo-2-methylpropane ...............................................................................

sodium hydroxide ............................................................................................. (2)

(ii) Write the rate equation for this reaction.

........................................................................................................................... (1)

(b) Use one set of the data to calculate the rate constant for this reaction. Include the unit of

the rate constant in your answer.

(2)

(c) The slowest step of the mechanism is the following reaction

(CH3)3CBr (CH3)3C+

+Br

Is your rate equation consistent with this information? Explain your answer.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

.................................................................................................................................... (1)

(d) In another series of experiments, the rate of the reaction was measured at different

temperatures. Complete the missing numbers in the table below.

temperature (T)

/K

1/temperature (1/T)

/K–1

rate

/mol dm3

s1

ln(rate)

300 3.33 × 10–3

3.35 × 104

8.00

310 3.23 × 10–3

7.47 × 104

7.20

320 3.13 × 10–3

1.66 × 103

6.40

330 3.03 × 10–3

4.09 × 103

5.50

340 2.94 × 10–3

9.10 × 103

4.70

350 1.66 × 102

(2)

(e) On the axes below plot a graph of ln(rate) on the vertical axis against 1/T on the

horizontal axis.

(2)

(f) Use the Arrhenius equation

ln(rate) = constant – R

EA (1/T)

to calculate the value of the activation energy, EA, for the reaction.

[R = 8.31 J K–1

mol–1

].

Show your working clearly and give your answer to 2 significant figures.

(2)

(Total 12 marks)

43. The equation below shows a possible reaction for producing methanol.

CO(g) + 2H2(g) CH3OH(l) ΔHο = 129 kJ mol

–1

(a) The entropy of one mole of each substance in the equation, measured at 298 K, is shown

below.

Substance

Sο

/J mol1

K1

CO(g) 197.6

H2(g) 130.6

CH3OH(l) 239.7

(i) Suggest why methanol has the highest entropy value of the three substances.

.............................................................................................................................

............................................................................................................................. (1)

(ii) Calculate the entropy change of the system, ΔSοsystem, for this reaction.

(2)

(iii) Is the sign of ΔSοsystem as expected? Give a reason for your answer.

.............................................................................................................................

.............................................................................................................................

............................................................................................................................. (1)

(iv) Calculate the entropy change of the surroundings ΔSοsurroundings, at 298 K.

(2)

(v) Show, by calculation, whether it is possible for this reaction to occur spontaneously

at 298 K.

(2)

(b) When methanol is produced in industry, this reaction is carried out at 400 ºC and 200

atmospheres pressure, in the presence of a catalyst of chromium oxide mixed with zinc

oxide. Under these conditions methanol vapour forms and the reaction reaches

equilibrium. Assume that the reaction is still exothermic under these conditions.

CO(g) + 2H2(g) CH3OH(g)

(i) Suggest reasons for the choice of temperature and pressure.

Temperature ........................................................................................................

.............................................................................................................................

.............................................................................................................................

.............................................................................................................................

Pressure ...............................................................................................................

.............................................................................................................................

............................................................................................................................. (3)

(ii) The catalyst used in this reaction is heterogeneous. Explain this term.

.............................................................................................................................

............................................................................................................................. (1)

(iii) Write an expression for the equilibrium constant in terms of pressure, Kp, for this

reaction.

CO(g) + 2H2(g) CH3OH(g)

(1)

(iv) In the equilibrium mixture at 200 atmospheres pressure, the partial pressure of

carbon monoxide is 55 atmospheres and the partial pressure of hydrogen is 20

atmospheres.

Calculate the partial pressure of methanol in the mixture and hence the value of the

equilibrium constant, Kp. Include a unit in your answer.

(2)

(c) The diagram below shows the distribution of energy in a sample of gas molecules in a

reaction when no catalyst is present. The activation energy for the reaction is EA.

(i) What does the shaded area on the graph represent?

............................................................................................................................. (1)

(ii) Draw a line on the graph, labelled EC, to show the activation energy of the

catalysed reaction. (1)

(Total 17 marks)

44. (a) Calculate the pH of a solution of sodium hydroxide of concentration 0.600 mol dm–3

,

assuming it is a strong base.

The ionisation constant for water, Kw, is 1.00 × 10–14

mol2 dm

–6.

(2)

(b) Calculate the pH of a solution of ethanoic acid of concentration 0.600 mol dm–3

.

The acid dissociation constant, Ka, for ethanoic acid is 1.70 × 10–5

mol dm–3

.

(3)

(c) A 100 cm3 sample of sodium hydroxide of concentration 0.600 mol dm

–3 is mixed with

200 cm3 of ethanoic acid of concentration 0.600 mol dm

–3.

(i) Write an equation for the reaction which occurs.

(1)

(ii) Calculate the number of moles of unreacted ethanoic acid remaining in the

resulting mixture.

(2)

(iii) Calculate the concentration, in mol dm3

, of the unreacted ethanoic acid in the

resulting mixture.

(1)

(iv) The mixture which forms is a buffer. Why does the pH of the mixture remain

constant when small quantities of solutions containing H+ or OH

– ions are added?

You may find it helpful to use equations in your explanation.

Addition of solution containing H+ ions. ...........................................................

.............................................................................................................................

.............................................................................................................................

Addition of solution containing OH– ions. .........................................................

.............................................................................................................................

............................................................................................................................. (3)

(v) The concentration of sodium ethanoate in the mixture is 0.200 mol dm3

. Calculate

the pH of the mixture, using your answer to (iii).

You may use the equation

pH = – log Ka – log [base]

[acid]

(2)

(Total 14 marks)

45. Pentanoic acid, C4H9COOH, is a weak acid with an acid dissociation constant,

Ka = 1.5 × 10–5

mol dm–3

.

(i) What is meant by the term weak in a weak acid?

.....................................................................................................................................

..................................................................................................................................... (1)

(ii) Write the expression for the Ka of C4H9COOH.

(1)

(iii) Calculate the pH of a 0.100 mol dm–3

solution of C4H9COOH.

(3)

(iv) On the grid below sketch the change in pH during the addition of 50.0 cm3 of

0.100 mol dm–3

sodium hydroxide solution to 25 cm3 of 0.100 mol dm

–3 pentanoic acid

solution.

14

12

10

8

6

4

2

0 10 20 30 40 50

Volume of sodium hydroxide added / cm3

pH

(4)

(v) Suggest, with reasoning, a suitable indicator for the titration in (iv).

Indicator pKind

Bromophenol blue 4.0

Methyl red 5.1

Thymol blue 8.9

Alizarin yellow 12.5

Indicator .....................................................................................................................

Reason ........................................................................................................................

..................................................................................................................................... (2)

(Total 11 marks)

46. This question is about the kinetics of the reaction between 2-bromo-2-methylpropane and

sodium hydroxide in a suitable solvent.

(CH3)3CBr + NaOH (CH3)3COH + NaBr

Equal volumes of 0.200 mol dm–3

solutions of the two reactants were mixed together and

maintained at a constant temperature of 30 C. The concentration of hydroxide ions was

determined at different times. The results are shown in the table below.

[OH–]

/mol dm–3

Time

/s

0.100 0

0.071 120

0.052 240

0.035 360

0.024 480

0.018 600

(a) Describe how the concentration of hydroxide ions could be determined during the

reaction.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

...................................................................................................................................... (3)

(b) (i) Plot a graph of hydroxide ion concentration (vertical axis) against time (horizontal

axis) on the grid below.

(2)

(ii) Mark on your graph TWO consecutive half-lives. Measure their values and write

them below.

First half-life ..........................................................................................................

Second half-life ..................................................................................................... (1)

(iii) What is the order of the reaction? Explain how you used your half-lives to arrive at

your answer.

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (1)

(iv) Explain why your answer to (iii) is an overall order.

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (1)

(v) Suggest a rate equation for this reaction.

Rate = (1)

(c) (i) What mechanism is likely to be operating in this reaction? Justify your answer.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (2)

(ii) Write equations to show the steps involved in your chosen mechanism for this

reaction.

(2)

(Total 13 marks)

47. The reaction between nitrogen and hydrogen can be used to produce ammonia.

N2(g) + 3H2(g) 2NH3(g) ΔH

ο = – 92.2 kJ mol

–1

Standard entropies are given below

Sο [N2(g)] = +191.6 J mol

–1 K

–1

Sο [H2(g)] = +130.6 J mol

–1 K

–1

Sο [NH3(g)] = +192.3 J mol

–1 K

–1

(a) Calculate the entropy change of the system, ΔSοsystem, for this reaction. Include a sign and

units in your answer.

(2)

(b) Calculate the entropy change of the surroundings, ΔSοsurroundings, at 298 K. Include a sign

and units in your answer.

(2)

(c) (i) Calculate the total entropy change, ΔSοtotal, at 298 K. Include a sign and units in

your answer.

(1)

(ii) Is this reaction feasible at 298 K? Justify your answer.

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (1)

(d) In industry the reaction is carried out at about 700 K using an iron catalyst and high

pressures.

(i) The yield of ammonia produced at equilibrium is less at 700 K than at 298 K, if the

pressure remains constant. In terms of entropy, explain why this happens.

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (1)

(ii) Higher pressures increase the yield of ammonia at equilibrium. Suggest a reason

why pressures greater than 300 atmospheres are not routinely used.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (1)

(iii) Iron is a heterogeneous catalyst. Explain what is meant by heterogeneous.

...............................................................................................................................

............................................................................................................................... (1)

(Total 9 marks)

48. Study the reaction scheme below, then answer the questions that follow.

(a) (i) Butanal contains a carbonyl group. State a chemical test for a carbonyl group and

describe the result of the test.

Test .........................................................................................................................

Result ..................................................................................................................... (2)

(ii) An isomer of butanal also possesses a carbonyl group, but cannot be oxidised by

acidified sodium dichromate(VI). Give the structural formula of this isomer and

its name.

Structural formula ..................................................................................................

Name ...................................................................................................................... (2)

(iii) Another isomer of butanal contains a carbonyl group and can be oxidised by

acidified sodium dichromate(VI). Draw the displayed formula of this isomer.

(1)

(b) Compound X is a colourless liquid that smells of pineapples.

(i) To what class of compounds does X belong?

............................................................................................................................... (1)

(ii) Ethanol, C2H5OH, reacts with butanoic acid to form compound X. Complete the

diagram below to show the structural formula of X and the other product.

(1)

(iii) Give the name of compound X.

............................................................................................................................... (1)

(iv) What type of attacking species is ethanol in this reaction?

............................................................................................................................... (1)

(c) Describe what you would expect to see during Reaction 2.

......................................................................................................................................

......................................................................................................................................

...................................................................................................................................... (1)

(d) Explain why Reaction 4 is far more vigorous than Reaction 3.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

...................................................................................................................................... (2)

(Total 12 marks)

49. This question is about butanoic acid, CH3CH2CH2CO2H.

(a) Butanoic acid can be described as a weak acid. Explain what is meant by weak as used in

this context.

......................................................................................................................................

......................................................................................................................................

...................................................................................................................................... (1)

(b) The acid dissociation constant, Ka, for butanoic acid is 1.50 10–5

mol dm–3

.

(i) Write the expression for Ka.

(1)

(ii) Calculate the pH of a 0.0100 mol dm–3

solution of the acid.

(2)

(c) A buffer solution can be made by mixing aqueous solutions of butanoic acid and sodium

butanoate.

Explain what is meant by a buffer solution.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

...................................................................................................................................... (2)

(d) The following equilibrium reactions are present in the buffer solution.

A CH3CH2CH2CO2H(l) CH3CH2CH2CO2

–(aq) + H

+(aq)

B H+(aq) +OH

–(aq) H2O(l)

(i) Which TWO of the substances behave as Brønsted–Lowry bases?

............................................................................................................................... (1)

(ii) Use the two equations, A and B, to explain how the buffer solution responds to the

addition of a solution containing hydroxide ions.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (2)

(iii) The pH of a buffer solution is given by the equation

pH = 1g Ka 1g [base]

[acid]

Using this equation, calculate the pH of a buffer solution made by mixing 100 cm3

of 0.0100 mol dm–3

butanoic acid solution with 300 cm3 of 0.00500 mol dm

–3

sodium butanoate solution.

[The Ka for butanoic acid is 1.50 × 10–5

mol dm–3

.]

(2)

(Total 11 marks)

50. (a) Propanoic acid, CH3CH2COOH, can be prepared from carbon dioxide and an organic

reagent.

Name this organic reagent and state the conditions for the preparation.

Reagent ........................................................................................................................

Conditions ....................................................................................................................

...................................................................................................................................... (3)

(b) Describe what you would see and write the equations for the reactions of propanoic acid

with:

(i) a solution of sodium carbonate

Observation ........................................................................................................

Equation ............................................................................................................. (2)

(ii) solid phosphorus pentachloride.

Observation ........................................................................................................

Equation ............................................................................................................. (2)

(c) Propanoic acid can also be prepared from propanal, CH3CH2CHO. State the reagents for

this conversion.

Reagents ...................................................................................................................... (2)

(d) 1-aminobutan-2-ol, CH3CH2CH(OH)CH2NH2, is an active ingredient in some deodorant

sprays.

It can be prepared from propanal by the following two-step process.

Step

1

Step

2

CH3CH2

C

H

O

CH3CH2CH(O

H

)

C

N

CH3CH2CH(OH)C

H2

N

H2

(i) For Step 1

State the reagents and conditions.

............................................................................................................................

............................................................................................................................

Name the type of reaction.

............................................................................................................................ (3)

(ii) For Step 2

State the reagents and conditions.

............................................................................................................................

............................................................................................................................

Name the type of reaction.

............................................................................................................................ (3)

(e) Write the structural formula of the organic product formed when 1-aminobutan-2-ol

reacts with:

(i) ethanoyl chloride, CH3COCl

(2)

(ii) hydrochloric acid.

(1)

(f) 1-aminobutan-2-ol exists as two isomers with the same structural formula.

Identify the type of isomerism and draw the TWO isomers, showing clearly the

difference between them.

Type of isomerism .......................................................................................................

(3)

(Total 21 marks)

51. (a) When silver carbonate is heated, it decomposes into silver oxide and carbon dioxide.

Ag2CO3(s) Ag2O(s) + CO2(g)

At 227 °C, the value of the equilibrium constant, Kp, is 1.48 atm.

(i) Write the expression for the equilibrium constant, Kp.

(1)

(ii) What is the pressure of carbon dioxide gas when silver carbonate is heated to a

temperature of 227 °C in a closed vessel?

(1)

(b) When nitrosyl chloride, NOCl, is heated, it dissociates reversibly into nitric oxide, NO,

and chlorine, Cl2, according to the equation

2NOCl(g) 2NO(g) + Cl2(g) ∆H = +75.6 kJ mol–1

(i) Write the expression for the equilibrium constant, Kp, for this reaction.

(1)

(ii) 1.00 mol of nitrosyl chloride was placed in a sealed container and heated to 500 °C.

Equilibrium was reached when 22.0% of the nitrosyl chloride had dissociated. The

pressure in the vessel was 5.00 atm.

Calculate the value of Kp at this temperature, stating its units.

(5)

(iii) State the effect of an increase in temperature on the value of the equilibrium

constant, Kp. Justify your answer.

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(iv) Hence suggest in which direction the position of equilibrium moves when the

temperature is increased. Justify your answer.

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(Total 12 marks)

52. (a) The first step in the esterification of ethanoic acid, CH3COOH, by ethanol in the presence

of a small quantity of concentrated sulphuric acid, is the reaction

CH3COOH + H2SO4 → CH3COOH2+ +

4HSO

In the space below the equation, identify the two acid base conjugate pairs. (2)

(b) Ethanoic acid, CH3COOH, is a weak acid and dissociates in water according to the

equation

CH3COOH(aq) + H2O(l) H3O+(aq) + CH3COO

–(aq)

Its acid dissociation constant, Ka, is

Ka = COOH][CH

]COO][CHO[H

3

–33

= 1.74 × 10–5

mol dm–3

(at 25 °C)

(i) The concentration of a solution of ethanoic acid can be determined by titrating a

25.0 cm3 sample in a conical flask against a standard solution of sodium hydroxide.

State whether the pH at the end point is less than 7, 7, or more than 7, and hence

name a suitable indicator for this titration.

pH at end point ..................................................................................................

Indicator ............................................................................................................. (2)

(ii) Ethanoic acid is only about 1% ionised in dilute solutions. Its enthalpy of

neutralisation is –55 kJ mol–1

, whereas the enthalpy of neutralisation of a strong

acid, such as hydrochloric acid, is –57 kJ mol–1

.

Explain why there is so little difference between these two values.

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................ (3)

(iii) Calculate the pH of a 0.140 mol dm–3

solution of ethanoic acid, clearly showing the

TWO assumptions that you have made.

Calculation

Assumptions

............................................................................................................................

............................................................................................................................

............................................................................................................................ (4)

(iv) To 50.0 cm3 of the solution in (III) , an equal volume of a 0.200 mol dm

–3 solution

of potassium ethanoate was added. Calculate the pH of the buffer solution

obtained.

(3)

(Total 14 marks)

53. (a) Define the terms

(i) Overall order of reaction

............................................................................................................................

............................................................................................................................ (1)

(ii) Rate constant

............................................................................................................................

............................................................................................................................ (1)

(b) In a kinetic study of the reaction

CH3I + OH– → CH3OH + I

–

At a certain temperature the following data were obtained:

Experiment [CH3I]

/mol dm–3

[OH–]

/mol dm–3

Initial rate

/mol dm–3

s–1

1 0.1 0.1 1 × 10–5

2 0.2 0.1 2 × 10–5

3 0.1 0.2 2 × 10–5

(i) State the order of reaction with respect to CH3I and with respect to OH– ions.

Give your reasons.

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................ (2)

(ii) Write the rate equation for the reaction.

............................................................................................................................ (1)

(iii) Calculate the value of the rate constant for this reaction, stating its units.

(2)

(c) The reaction

CH3CH2Br + OH– → CH3CH2OH + Br

–

has an SN2 mechanism that proceeds through a transition state.

(i) Draw the mechanism, showing the structure of the transition state.

(3)

(ii) Draw a reaction profile for this exothermic reaction. Show the energy level of the

transition state on the profile.

(2)

(Total 12 marks)

54. Persulphate ions, S2O –2

8 slowly oxidise arsenic(III) acid, H3AsO3 in aqueous solution according

to the equation

S2O –2

8 + H3AsO3 + H2O → 2SO –2

4 + H3AsO4 + 2H+

25 cm3 of a 1.0 mol dm

–3 solution of potassium persulphate was mixed with 25 cm

3 of a

solution of arsenic(III) acid of the same concentration.

At timed intervals, small potions of the reation mixture were analysed to determine the

concentration of persulphate ion, [S2O –2

8 ].

The results are shown below.

Time

/ minutes

[ 282OS ]

/ mol dm–3

0 1.0

5 0.76

10 0.62

15 0.52

20 0.44

30 0.35

(a) (i) On the grid below, plot a graph of the concentration of persulphate ions against

time.

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.30 5 10 15 20 25 30

Time / min

[S O ]/ mol dm–3

2–2 8

(2)

(ii) Draw a tangent to the curve at the point where [S2O –28 ] = 0.50 mol dm

–3 and use it

to calculate the slope of the curve at that point. Give your answer to two significant

figures.

Slope: .............................. (4)

(b) The rate of the reaction at a particular concentration of reactant can be measured from the

slope of the graph at that concentration.

The initial rate, which is the rate when the concentrations of persulphate ions, S2O –2

8 ,

and arsenic(III) acid, H3AsO3, are both 1.0 mol dm–3

, was found to be 0.060 mol dm–

3 min

–1.

(i) Use your answer to (a)(ii) to show that the ratio of the initial rate to the rate when

[S2O –2

8 ] and [H3AsO3] are 0.50 mol dm–3

is approximately 4:1. Use this ratio to

deduce the overall order of reaction.

(3)

(ii) Suggest TWO rate equations that agree with the order of the reaction that you have

deduced in (i). How could the experiment be adapted to distinguish between these

two rate equations?

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................ (5)

(Total 14 marks)

55. (a) (i) Give the formula of the ion which causes an aqueous solution to be alkaline.

........................................................... (1)

(ii) Explain why a 0.1 mol dm–3

solution of ammonia has a lower pH than a

0.1 mol dm–3

solution of sodium hydroxide.

................................................................................................................................

................................................................................................................................

................................................................................................................................ (1)

(b) Using the letters P, Q and R arrange the following in order of increasing pH

de-ionised water 0.1 mol dm–3

0.1 mol dm–3

ethanoic acid hydrochloric acid

P Q R

.................................................................. (1)

(Total 3 marks)

56. (a) The distribution of the energy of particles in a gas at temperature T1 is shown below.

(i) On the diagram above, draw the distribution of energy of particles at a lower

temperature, T2. (2)

(ii) Use the diagram to explain why the rate of a reaction increases with an increase in

temperature.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

............................................................................................................................... (3)

(iii) Explain fully why a catalyst increases the rate of a reaction.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................ (2)

(b) The fermentation of glucose is an exothermic reaction and is catalysed by enzymes in

yeast.

C6H12O6(aq) → 2C2Η5ΟΗ(aq) + 2CO2(g)

The reaction is slow at room temperature.

(i) Describe, with the aid of a diagram, an experiment you could do to follow the

progress of this reaction at different temperatures.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................ (4)

(ii) Would you expect ∆Ssystem to be positive or negative for this reaction? Justify your

answer with TWO pieces of evidence.

................................................................................................................................

...............................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................ (2)

(iii) Deduce the sign of ∆Ssurroundings. Show your reasoning.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................ (2)

(Total 15 marks)

57. Maleic acid has the structure shown below.

It is a dioic acid and is one of a pair of geometric isomers.

(a) What is the systematic name for maleic acid?

....................................................................................................................................... (2)

(b) Write the equation for the reaction of sodium hydroxide with maleic acid,

HO2CCH=CHCO2H, to form disodium maleate (state symbols are not required).

(2)

(c) Maleic acid has two acid dissociation constants with the following values

Ka1 = 1.48 × 10–2

mol dm–3

Ka2 = 8.51 × 10–7

mol dm–3

(i) Explain why maleic acid has two different Ka values.

................................................................................................................................

................................................................................................................................

................................................................................................................................ (2)

(ii) Complete an equation for the first dissociation of maleic acid.

HO2CCH=CHCO2H

(1)

(iii) Maleic acid is a weak acid. Calculate the pH of a solution of maleic acid of

concentration 0.0100 mol dm–3

using the value of Ka1 but not Ka2.

(2)

(iv) Both carboxylic acid groups in maleic acid do dissociate. Suggest how your answer

in (c)(iii) might be affected if you consider Ka2 in addition to Ka1?

................................................................................................................................

................................................................................................................................ (1)

(Total 10 marks)

58. In the first stage of an industrial process for purifying nickel, carbon monoxide is passed over

impure nickel at 323 K. Gaseous nickel tetracarbonyl, Ni(CO)4, is formed.

Ni(s) + 4CO(g) Ni(CO)4(g) ∆Hο = –191 kJ mol

–1

(a) (i) Calculate ∆Sοsystem for this reaction given the following standard entropy values.

Substance

Sο

/J mol–1

K–1

Ni(s) +29.9

CO(g) +197.6

Ni(CO)4(g) +313.4

Include a sign and units in your answer.

(2)

(ii) Refer to the equation above and comment on the sign of your answer.

................................................................................................................................

................................................................................................................................

................................................................................................................................ (1)

(iii) Calculate ∆Sοsurroundings at 323 K. Include a sign and units in your answer.

(2)

(iv) Deduce the direction of this reaction at 323 K. Justify your answer.

................................................................................................................................

................................................................................................................................ (1)

(b) (i) Write the expression for the equilibrium constant, Kp, for this reaction.

(1)

(ii) 100 moles of gaseous carbon monoxide is mixed with excess solid nickel at 323 K

in a vessel kept at 1.00 atmosphere pressure. At equilibrium, 1.00 mole of the

carbon monoxide has reacted.

Complete the table below and then calculate the value of Kp at this temperature.

Include the units of Kp in your answer.

Substance Moles at start Moles at

equilibrium

Partial pressure, peq

/atm

Ni(CO)4 0

CO 100 99.0

(4)

(iii) As Kp has such a small value, suggest THREE ways in which this industrial

process could be improved to increase profitability. Justify each of your

suggestions.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................ (3)

(c) The second stage of this process is to recover the nickel from the nickel tetracarbonyl,

Ni(CO)4. By considering your calculations of the entropy changes, suggest how this

could be done. Justify your suggestion.

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

.......................................................................................................................................

....................................................................................................................................... (2)

(Total 16 marks)

59. (a) State Hess‘s Law.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(b) Methane burns in oxygen.

CH4(g) + 2O2(g) CO2(g) + 2H2O(g)

(i) Calculate the enthalpy change for this reaction, using the bond enthalpies

given below.

Bond enthalpy

/ kJ mol–1

C – H +435

O = O +498

C = O +805

H – O +464

(3)

(ii) State the name of this enthalpy change.

........................................................................................................................... (1)

(iii) The value of this enthalpy change, under standard conditions, is –890 kJ mol–1

.

State the meaning of standard conditions.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(iv) Suggest, with a reason, why the enthalpy change calculated in (i) is different from

the standard value quoted in (iii).

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(c) Although the reaction between methane and oxygen is exothermic, it does not occur

unless the mixture is ignited.

Use these facts to explain the difference between thermodynamic and kinetic stability.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (4)

(Total 14 marks)

60. The weak acid methanoic acid, HCOOH, sets up the following equilibrium in water at 298 K:

HCOOH(aq) + H2O(l) H3O+(aq) + HCOO

–(aq)

The acid dissociation constant, Ka, for methanoic acid at 298 K is 1.78 × 10–4

mol dm–3

.

(a) A 0.200 mol dm–3

solution of methanoic acid has a pH of 2.2 at 298 K.

20.0 cm3 of this solution is titrated with 0.100 mol dm

–3 sodium hydroxide solution until

excess alkali has been added.

On the grid below, sketch the titration curve you would expect for this reaction.

pH

14

12

10

8

6

4

2

0

10 20 30 40 50 60

Volume of sodium hydroxide solution/ cm3

(4)

(b) Equal volumes of 0.500 mol dm–3

methanoic acid and 0.250 mol dm–3

sodium

methanoate solution are mixed to make a buffer solution.

(i) Define the term buffer solution.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) Calculate the pH of this buffer solution.

(3)

(iii) Explain, with the aid of equations, how this mixture acts as a buffer solution.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (4)

(Total 13 marks)

61. 2-bromo-2-methylbutane reacts with aqueous sodium hydroxide in a substitution reaction.

CH

C

3

C H2 5

Br

CH3 + OH

CH

C

3

C H2 5 CH3

OH

+ Br– –

(a) The rate of reaction can be followed by measuring the concentration of 2-bromo-2-

methylbutane at various times.

In one such experiment, a known amount of 2-bromo-2-methylbutane was added to a

large excess of aqueous sodium hydroxide. The following results were obtained.

Time/min Concentration of 2-bromo-2-methylbutane/mol dm–3

0 0.96

10 0.61

20 0.38

30 0.24

40 0.15

50 0.10

(i) Plot a graph of the concentration of 2-bromo-2-methylbutane on the y (vertical)

axis against time on the x (horizontal) axis.

1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

0 10 20 30 40 50 60

Time / min

Con

centr

atio

n o

f 2-b

rom

o-2

-met

hylb

uta

ne

/ m

ol

dm

–3

(2)

(ii) Show TWO successive half-life measurements on your graph and write their values

below.

First half-life ............................................................

Second half-life ............................................................ (2)

(iii) What is the order of reaction with respect to 2-bromo-2-methylbutane?

Give a reason for your answer.

Order .........................................................

Reason ...............................................................................................................

............................................................................................................................ (2)

(b) When the reaction is repeated using equal concentrations of 2-bromo-2-methylbutane and

aqueous sodium hydroxide, the same results are obtained.

(i) What is the order of reaction with respect to hydroxide ions?

........................................................................................................................... (1)

(ii) Write the rate equation for the reaction.

........................................................................................................................... (1)

(iii) Write a mechanism for the reaction which is consistent with your rate equation.

(3)

(c) The reaction between 2-bromobutane, C2H5CHBrCH3, and aqueous sodium hydroxide

proceeds by the same mechanism as in (b)(iii).

Use the mechanism to explain why the reaction of a single optical isomer of 2-

bromobutane produces a mixture that is no longer optically active.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 14 marks)

62. Potassium hydroxide solution, KOH(aq), is used to peel peaches commercially. The peaches are

placed in a 7% solution (7.00 g per 100 cm3 of solution) for 3 minutes. The peaches are then

washed, cut in half and frozen.

(a) (i) Calculate the concentration, in mol dm–3

, of the potassium hydroxide solution.

(2)

(ii) Calculate the pH of this solution.

[Kw = 1.00 × 10–14

mol2 dm

–6]

(2)

(b) The concentration of the potassium hydroxide solution must not fall below

1.00 mol dm–3

. This is checked at intervals by the titration of 25.0 cm3 of the solution

with 0.750 mol dm–3

sulphuric acid.

(i) Write a balanced equation for the complete neutralisation of sulphuric acid with

potassium hydroxide.

(1)

(ii) Calculate the lowest acceptable titration value before more potassium hydroxide

must be added to the solution.

(2)

(iii) Sketch a graph showing how the pH changes when 30 cm3 (an excess) of 0.750

mol dm–3

sulphuric acid is added to 25.0 cm–3

of 1.00 mol dm–3

potassium

hydroxide.

16

12

8

4

0

–40 10 20 30

Volume of 0.750 mol dm sulphuric acid added/cm–3 3

pH

(4)

(iv) Suggest a suitable indicator to use for this titration. Use your graph to justify your

choice.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(c) Suggest a safety check that should be made before the peaches are frozen. Why is this

check necessary?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 15 marks)

63. One step in the manufacture of nitric acid is the reaction between nitrogen(II) oxide and oxygen

to form nitrogen(IV) oxide.

2NO(g) + O2(g) 2NO2(g) ΔH = –114 kJ mol–1

(a) (i) Use the equation to suggest the sign of ΔSsystem for the forward reaction. Justify

your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) What is the sign of ΔSsurroundings for the forward reaction? Justify your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(b) (i) Write the expression for Kp for this reaction.

What are the units of Kp in this reaction?

Units .............................................. (2)

(ii) Suggest how the temperature and pressure could be altered to make nitrogen(IV)

oxide more economically. Justify your suggestions by considering both yield and

rate.

Temperature

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Pressure

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (4)

(c) (i) What property would allow you to follow the progress of this reaction? Justify your

answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) In a series of experiments, the following results were obtained.

Experiment [NO(g)]

/mol dm–3

[O2(g)]

/mol dm–3

Initial rate

/mol dm–3

s–1

1 1.0 × 10–3

1.0 × 10–3

8.0 × 10–6

2 2.0 × 10–3

1.0 × 10–3

3.2 × 10–5

3 2.0 × 10–3

2.0 × 10–3

6.4 × 10–5

What is the order of the reaction with respect to NO(g)? Justify your answer.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

What is the order of the reaction with respect to O2(g)?

........................................................................................................................... (1)

(iii) What is the rate equation for this reaction?

(1)

(iv) What is the overall order for this reaction?

.................................................................................... (1)

(v) Calculate the rate constant, k, for this reaction. Include units with your answer.

(2)

(d) Suggest why this reaction takes place quickly at room temperature and pressure.

..................................................................................................................................... (1)

(Total 20 marks)

64. This question is about compounds with the molecular formula C4H8O.

(a) (i) Draw the displayed formulae of TWO isomers, A and B, which are both aldehydes.

Give their systematic names.

A B

Name ....................................................... ....................................................... (4)

(ii) Suggest an instrumental method by which these isomers, A and B, could be

distinguished.

Outline how the results would differ.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(b) Substance C, butanone, is another isomer of C4H8O.

(i) Name a reagent which results in the same observation when it reacts with all three

isomers, A, B and C.

Reagent .............................................................................................................

...........................................................................................................................

Observation ......................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) Name a reagent where the resulting observation for C would be different from that

for A and B.

Reagent .............................................................................................................

...........................................................................................................................

Observation with C ...........................................................................................

...........................................................................................................................

...........................................................................................................................

Observation with A and B ................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(c) (i) Suggest structural formulae for TWO more isomers of C4H8O, D and E, which are

cyclic and react with sodium to give off hydrogen.

D E (2)

(ii) Both A and B can be oxidised to carboxylic acids. These acids will then react with

either of the isomers D or E in the presence of a strong acid as a catalyst.

What is the name given to the products of this type of reaction?

........................................................................................................................... (1)

(iii) For one of the carboxylic acids formed from A or B and one of the isomers D or E,

draw a displayed formula of the product formed when they react together.

(2)

(Total 16 marks)

65. (a) (i) Calculate the pH of 0.050 mol dm–3

hydrochloric acid.

(1)

(ii) Calculate the concentration of hydroxide ions, in mol dm–3

, in this solution.

At this temperature, Kw = 1.00 × 10–14

mol2 dm

–6.

(1)

(b) Phosphoric(V) acid, H3PO4, is a weak acid, forming the following equilibrium in water:

H3PO4(aq) + H2O(l) H2PO4–(aq) + H3O

+(aq)

(i) Write an expression for the acid dissociation constant, Ka, for phosphoric(V) acid.

(1)

(ii) Given that a 0.500 mol dm–3

solution of phosphoric(V) acid has a pH of 1.20,

calculate the value of Ka, stating its units.

Assume that there is no further dissociation of the H2PO4– ion.

(4)

(c) The H2PO4– ion formed when phosphoric(V) acid is added to water can dissociate further

into HPO42–

.

H2PO4–(aq) + H2O(l) HPO4

2–(aq) + H3O

+(aq)

.................. .................. .................. ..................

(i) In the spaces below the equation, identify the acid base conjugate pairs. (2)

(ii) Explain why very little dissociation of the H2PO4– ion occurs in solutions of

phosphoric(V) acid.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(d) The change in pH when 25.0 cm3 of 0.100 mol dm

–3 phosphoric(V) acid is titrated with

sodium hydroxide solution of the same concentration can be seen on the graph below.

7

6

5

4

3

2

110 20 30

pH

Volume of 0.100 mol dm sodiumhydroxide solution added/ cm 3

–3

From the list below, select a suitable indicator for this titration. Justify your choice.

pKIn

bromocresol green 4.7

bromothymol blue 7.0

phenolphthalein 9.3

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 12 marks)

66. Hydrogen sulphide, H2S, is partially decomposed when heated.

2H2S(g) 2H2(g) + S2(g) ∆H = +170 kJ mol–1

0.500 mol of gaseous H2S were placed in a flask of volume 20.0 dm3 and heated until

equilibrium was reached.

(a) Write an expression for the equilibrium constant, Kc, for this reaction.

(1)

(b) When equilibrium was established, there were 0.350 moles of hydrogen sulphide in the

flask.

Calculate the value of Kc at this temperature to two significant figures. State its units.

(5)

(c) The pressure in the reaction vessel was increased. By considering any change in Kc,

explain the effect on the equilibrium position.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(d) State the effect, if any, on the value of Kc of:

(i) adding a catalyst,

...........................................................................................................................

........................................................................................................................... (1)

(ii) increasing the temperature.

...........................................................................................................................

........................................................................................................................... (1)

(Total 11 marks)

67. (a) Explain what is meant by the following terms.

Rate of reaction ...........................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Overall order of a reaction ..........................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(b) Two gases, A and B, react according to the equation

A + 3B AB3

A series of experiments carried out at 298 K gave the following results.

Experiment Initial

concentration of

A

/ mol dm–3

Initial

concentration of

B

/ mol dm–3

Initial rate of

reaction

/ mol dm–3

min–1

1 0.100 0.100 0.00200

2 0.100 0.200 0.00798

3 0.200 0.100 0.00399

(i) State the order of reaction with respect to each of the reactants. Justify your

answer.

Reactant A ........................................................................................................

...........................................................................................................................

...........................................................................................................................

Reactant B ........................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(ii) Write the rate equation for the reaction between A and B.

........................................................................................................................... (1)

(iii) Use the experimental data from Experiment 1 to calculate the rate constant,

including units.

(2)

(iv) Suggest a possible mechanism for the reaction between A and B, leading to the

formation of AB3. Identify the rate-determining step.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(c) The rae constant, k, for the reaction in (b) was measured at different temperatures.

The following data were obtained.

log10 k T

1/K

–1

–2.70 0.00303

–3.39 0.00315

–4.09 0.00327

–4.43 0.00333

(i) Plot a graph of log10 k against T

1, on the grid below.

–5.0

–4.0

–3.0

–2.0

0.00300 0.00310 0.00320 0.00330

log k10

/K–11

T

(2)

(ii) The Arrhenius equation can be written

log10 k = constant

TR

E 1

30.2

a

where R = 8.31 J mol–1

K–1

.

A graph of log10 k against T

1 has a gradient of

R

E

30.2

a.

Calculate the gradient of the graph and hence calculate the value of activation

energy, Ea.

(2)

(Total 15 marks)

68. This question is about the reaction between calcium carbonate and hydrochloric acid.

CaCO3(s) + 2HCl(aq) CaCl2(aq) + CO2(g) + H2O(l)

One method of studying the kinetics of this reaction is to measure the volume of carbon dioxide

given off at various timed intervals when using an excess of calcium carbonate.

(a) Suggest TWO other methods for following this reaction. Explain your choices.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(b) Suggest why the volume of carbon dioxide given off in the first few seconds of the

reaction is an unreliable measure of the initial rate of the reaction.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(c) In an experiment, the following results were obtained.

Time

/ s

Volume of CO2

Vt/cm3

(Vfinal – Vt)

/ cm3

5 3 85

35 42 46

65 62 26

95 72

125 79

155 84

185 87

(i) What was the final volume, Vfinal?

............................................................................ (1)

(ii) Complete the table. (1)

(iii) To what is (Vfinal – Vt) proportional?

........................................................................................................................... (1)

(iv) Plot these results on the grid below.

100

80

60

40

20

00 100 200

time / s

(V –V )/ cm

final t3

(2)

(v) On your graph measure and record THREE successive half-lives. Deduce the order

of the reaction. Justify your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(vi) Give the rate equation for this reaction.

(1)

(vii) What are the units of the rate constant?

.............................................................. (1)

(d) What would you expect the signs of Ssystem and Stotal to be for the reaction between

calcium carbonate and hydrochloric acid? Justify your answers.

Ssystem ..........................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Stotal ............................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (4)

(Total 17 marks)

69. For each of the following reactions, give the names of all of the organic products.

Also give the type or mechanism as indicated for each reaction,

(a) CH3CO2H + NaOH CH3CO2Na + H2O

Name of organic product ..........................................................................................

Type of reaction .......................................................................................... (2)

(b) O CH3

+ ICl + HCl

O CH3

I

Name of organic product .........................................................................................

Type of reaction ......substitution...............................................................

Mechanism ......................................................................................... (2)

(c) CH3COCl + 2NH3 CH3CONH2 + NH4Cl

Name of organic product .........................................................................................

Type of reaction ......substitution...............................................................

Mechanism ......................................................................................... (2)

(d) CH2—O—CO(CH2)8CH3 CH2OH

CH—O—CO(CH2)8CH3 + 3H2O (aq)H

CHOH + 3CH3(CH2)8CO2H

CH2—O—CO(CH2)8CH3 CH2OH

Names of products .........................................................................................

.........................................................................................

Type of reaction ......................................................................................... (3)

(Total 9 marks)

70. This question is about a compound, A, used as a food flavouring. It has the molecular formula,

C9H8O.

(a) For each of the following pieces of information, state what can be deduced about the a

structure of A.

(i) A burns with a very sooty flame.

........................................................................................................................... (1)

(ii) A reacts with Brady‘s Reagent (2,4-dinitrophenylhydrazine) to give an orange

precipitate.

........................................................................................................................... (1)

(iii) When A is heated with Benedict‘s solution, a red precipitate forms.

........................................................................................................................... (1)

(iv) A decolorises bromine water.

........................................................................................................................... (1)

(v) A is the cis isomer.

...........................................................................................................................

........................................................................................................................... (1)

(vi) Use all of the above information to draw the displayed formula of A.

(2)

(b) Compound A can be converted to benzoic acid, C6H5CO2H, which is formed as a white

precipitate.

(i) The precipitate can be purified by recrystallisation, using water as the solvent.

Describe how you would carry out this recrystallisation, explaining the reason for

each step in your method.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (5)

(ii) How would you check that the purification had been successful?

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(c) (i) Write the equation for the reaction which occurs when solid benzoic acid is added

to sodium carbonate solution. Include state symbols in your equation.

(2)

(ii) Benzoic acid is slightly soluble in water. Write the equation for the dissociation of

benzoic acid and hence the expression for the acid dissociation constant, Ka.

(2)

(iii) Calculate the pH of a 0.00100 mol dm–3

solution of benzoic acid.

[Ka for benzoic acid is 6.30 × 10–5

mol dm–3

.]

(3)

(d) Give the name or formula of an organic compound which, when mixed with a solution of

benzoic acid, forms a buffer solution.

(1)

(Total 21 marks)

71. Dichloroethanoic acid reacts with pent-1-ene as shown by the following equation:

CHCl2CO2H(l) + C5H10(l) CHCl2CO2C5H11(l)

(a) Give the name of the product of this reaction and also the name for the new functional

group it contains.

.....................................................................................................................................

..................................................................................................................................... (2)

(b) In an experiment to determine the equilibrium constant, 1.00 mol of dichloroethanoic acid

was mixed with 2.30 mol of pent-1-ene. The total volume remained at 300 cm3

throughout. When equilibrium had been reached, it was found that 0.40 mol of

dichloroethanoic acid was left.

(i) List the steps in the experiment you would carry out to determine the concentration

of dichloroethanoic acid present at equilibrium.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (4)

(ii) Give the expression for the equilibrium constant, Kc, for this reaction.

(1)

(iii) Complete the table for the number of moles and concentrations at equilibrium.

Substance Number of

moles at start

Number of moles

at equilibrium

Concentration at

equilibrium

/mol dm–3

CHCl2COOH 1.00 0.40 1.33

C5H10 2.30

CHCl2COOC5H11 0

(3)

(iv) Calculate the value of Kc, and give its units.

(3)

(Total 13 marks)

72. (a) Define the term standard enthalpy of formation.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(b) In the Haber process, ammonia is manufactured from nitrogen and hydrogen as shown in

the equation.

N2(g) + 3H2(g) 2NH3(g)

(i) Use the bond enthalpies below to calculate the standard enthalpy of formation of

ammonia.

Bond Bond enthalpy / kJ mol–1

N≡N in N2 +945

H–H in H2 +436

N–H in NH3 +391

(4)

(ii) Draw a labelled enthalpy level diagram for the formation of ammonia in the Haber

process.

Enthalpy

(2)

(iii) State the temperature used in the Haber process and explain in terms of the rate of

reaction and position of equilibrium, why this temperature is chosen.

Temperature .......................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(iv) Identify the catalyst used in the Haber process and state what effect, if any, it has

on the equilibrium yield of ammonia.

Catalyst ................................................................

Effect on yield ................................................................................................... (2)

(v) Explain why it is necessary to use a catalyst in this process.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(c) The pressure used in the Haber process is 250 atmospheres.

(i) State and explain an advantage of increasing the pressure to 1000 atmospheres.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) Suggest a disadvantage of using a pressure of 1000 atmospheres.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(Total 18 marks)

73. (a) Methanoic acid, HCOOH, is a weak acid. Explain what is meant by the terms weak and

acid.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(b) Write a balanced equation, including state symbols, for the reaction between aqueous

solutions of methanoic acid and sodium carbonate.

..................................................................................................................................... (2)

(c) The following equilibrium is set up when methanoic acid dissociates in water:

HCOOH(aq) + H2O(1) HCOO–(aq) + H3O

+(aq)

(i) There are two conjugate acid-base pairs in the above equation.

Identify them by completing the sentences below:

Formula of one acid is .......................................................... .

The formula of its conjugate base is .......................................................... . (1)

Formula of the other acid is .......................................................... .

The formula of its conjugate base is .......................................................... . (1)

(ii) Write the expression for the acid dissociation constant, Ka, for methanoic acid.

(1)

(iii) Calculate the pH of a 0.100 mol dm–3

solution of methanoic acid at 298 K.

[Ka for methanoic acid is 1.60 × 10–4

mol dm–3

at 298 K]

(3)

(d) A buffer solution is made up by mixing equal volumes of 0.100 mol dm–3

methanoic acid

and 0.400 mol dm–3

sodium methanoate.

(i) Calculate the pH of the buffer solution obtained.

(3)

(ii) Explain why the pH of this mixture of methanoic acid and sodium methanoate

remains almost constant when a small quantity of an acidic solution, containing

hydrogen ions, or a small quantity of an alkaline solution, containing hydroxide

ions, is added.

In your explanation include equations to show the effect of adding hydrogen ions

and of adding hydroxide ions.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(Total 16 marks)

74. One stage in the manufacture of sulphuric acid is

2SO2(g) + O2(g) 2SO3(g)

The equilibrium constant Kp =

22

3

O2SO

2SO

pp

p

(a) 10.0 mol of SO2 and 5.00 mol of O2 were allowed to react. At equilibrium, 90.0% of the

SO2 was converted into SO3.

(i) Calculate the number of moles of SO2, O2 and SO3 present in the equilibrium

mixture.

(2)

(ii) Calculate the mole fractions of SO2, O2 and SO3 at equilibrium.

(1)

(iii) Assuming that the total pressure of the equilibrium mixture was 2.00 atm, calculate

the partial pressures of SO2, O2 and SO3 at equilibrium.

(1)

(iv) Calculate the value of Kp.

(2)

(b) The reaction between sulphur dioxide and oxygen is exothermic.

(i) State the effect, if any, on Kp of increasing the temperature at constant pressure.

........................................................................................................................... (1)

(ii) Use your answer to (i), and the expression Kp =

22

3

O2SO

2SO

pp

p

to explain the effect

on the position of equilibrium of increasing the temperature at constant pressure.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(c) The reaction was repeated at a higher pressure whilst maintaining a constant temperature.

(i) State the effect, if any, of an increase in the total pressure on the value of Kp.

............................................................................... (1)

(ii) State the effect, if any, of this increase in pressure on the amount of sulphur

trioxide in the equilibrium mixture.

............................................................................... (1)

(d) State the effect, if any, of a catalyst on:

(i) Kp

............................................................................... (1)

(ii) the equilibrium position.

............................................................................... (1)

(Total 13 marks)

75. (a) What is the formula of the ion found in all acidic solutions?

..................................................................................................................................... (1)

(b) Which of the following substances would form an acidic solution in water?

A CH4 B NaOH C HCO2H

D NH3 E HNO3

..................................................................................................................................... (2)

(Total 3 marks)

76. When barium nitrate is heated it decomposes as follows:

Ba(NO3)2(s) → BaO(s) + 2NO2(g) + ½O2(g) ΔH = +505.0 kJ mol–1

(a) Use the following data when answering this part of the question.

Substance Standard entropy,

Sο / J mol

–1 K

–1

Ba(NO3)2(s) + 213.8

BaO(s) + 70.4

NO2(g) + 240.0

O2(g) + 205.0

(i) Explain why:

• Sο [NO2(g)] is greater than S

ο [BaO(s)]

...........................................................................................................................

...........................................................................................................................

• Sο [Ba(NO3)2(s)] is greater than S

ο [BaO(s)].

...........................................................................................................................

........................................................................................................................... (2)

(ii) Calculate the entropy change of the system, ΔSοsystem, for this reaction. Include a

sign and units in your answer.

(2)

(b) Calculate the entropy change of the surroundings, ΔSοsurroundings, for the reaction at 298 K.

Include a sign and units in your answer. (2)

(c) Calculate ΔSοtotal, and explain the significance of the sign for this value.

..................................................................................................................................... (2)

(d) Calculate the minimum temperature at which the decomposition of barium nitrate should

occur.

You can assume that ΔH and ΔSsystem are not affected by a change in temperature.

(2)

(Total 10 marks)

77. This question is about butanal, CH3CH2CH2CHO, and several related compounds.

(a) What would you see when Brady‘s reagent is added to a sample of butanal?

..................................................................................................................................... (1)

(b) F, G and H are three isomers of butanal which are each tested with sodium, Benedict‘s

reagent and Brady‘s reagent. The results are shown in the table below.

Key: = positive result

= negative result

Sodium Benedict‘s reagent Brady‘s reagent

F

G

H

Suggest structural formulae for F, G and H.

F

G

H

(3)

(c) An ester with the formula, CH3CH2CH2CO2CH2CH3, is heated under reflux with aqueous

sodium hydroxide.

(i) Give ONE advantage of ―heating under reflux‖, rather than simply boiling the two

liquids together in a beaker.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(ii) Name the ester.

........................................................................................................................... (1)

(iii) Name the TWO products of this reaction.

........................................................................................................................... (2)

(iv) What type of reaction is taking place?

........................................................................................................................... (1)

(Total 9 marks)

78. The reaction between peroxodisulphate and iodide ions occurs as follows:

aq)(Iaq)(SO2aq)(2Iaq)(OS 224

282

Initial rates for this reaction can be determined by a method known as an ‗iodine clock‘.

A mixture of potassium iodide, sodium thiosulphate and starch is made up, and a clock started

when a solution of potassium peroxodisulphate is added. When enough iodine has been formed

to react with all the sodium thiosulphate, the excess iodine suddenly forms a blue-black

complex with the starch. At this point the clock is stopped, and the time taken.

(a) In one particular experiment, the volumes of the reactants used were as follows:

Volume of

K2S2O8(aq)

/ cm3

Volume of

KI(aq) / cm3

Volume of

Na2S2O3(aq)

/ cm3

Volume of

starch solution /

cm3

Volume of

water / cm3

Time taken

/ s

10.0 10.0 5.0 1.0 14.0 5

(i) The concentration of the sodium thiosulphate used was 0.010 mol dm–3

. Calculate

the number of moles of thiosulphate ions, 232OS , in the mixture.

(1)

(ii) Iodine reacts with thiosulphate ions as shown below:

aq)(OSaq)(I2(aq)O2Saq)(I 264

2322

Calculate the number of moles of iodine which had reacted when the clock was

stopped.

(1)

(iii) Calculate the rate of formation of iodine in mol dm–3

s–1

.

(2)

(b) Further experiments were carried out and the results are shown below.

Experiment [ 282OS (aq)] / mol dm

–3 [I

–(aq)] / mol dm

–3 Rate / mol dm

–3 s

–1

1 0.0100 0.0200 2.74 × 10–5

2 0.0100 0.0400 5.47 × 10–5

3 0.0300 0.0800 3.28 × 10–4

(i) What is the order of reaction with respect to iodide ions, I–?

........................................................................................................................... (1)

(ii) Deduce the order of reaction with respect to peroxodisulphate ions, 282OS .

Show how you arrived at your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(iii) Use your answers to (i) and (ii) to write an overall rate equation for the reaction.

(1)

(iv) Use the data from experiment 1 to calculate the rate constant for this reaction.

Give the units for the rate constant.

(2)

(Total 9 marks)

79. 10.0 cm3 of a solution of butanoic acid, CH3CH2CH2CO2H, of concentration 0.00660 mol dm

–3,

was titrated with a solution of aqueous ammonia using a pH probe.

The pH was recorded throughout, and the results were plotted as shown below.

11

10

9

8

7

6

5

4

3

2

1

0

pH

0 10 20 30 40 50 60

Volume of ammonia added / cm 3

X

Y

(a) (i) Using the pH of butanoic acid from the graph, calculate the initial hydrogen ion

concentration.

(2)

(ii) Write the expression for the acid dissociation constant, Ka, for an aqueous solution

of butanoic acid.

(1)

(iii) Calculate the value of Ka making the usual assumptions. Give your answer to two

significant figures.

(2)

(b) (i) Write an equation for the reaction between butanoic acid and ammonia. State

symbols are not required.

(1)

(ii) Name the two compounds, apart from water, which are present in the mixture

between X and Y shown on the graph.

........................................................................................................................... (2)

(iii) What type of mixture is present between X and Y? What evidence is there for your

answer by reference to the graph?

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(iv) Explain why it is not possible to carry out this titration using an indicator.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(v) Use the graph to estimate the end-point of the titration. Hence calculate the

concentration of the ammonia solution.

(2)

(Total 13 marks)

80. (i) Define the term enthalpy of hydration, ΔHhyd, of an ion.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(ii) The table below gives some information about the sulphates of the Group 2 elements

magnesium and barium.

sulphate lattice energy

/ kJ mol–1

hydration

enthalpy of cation

/ kJ mol–1

solubility

/ mol dm–3

MgSO4 –2874 –1920 1.83

BaSO4 –2374 –1360 9.43 × 10–6

Use the lattice energy and hydration enthalpy values to explain the difference in the

solubility of the two salts.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (4)

(Total 6 marks)

81. (a) Sketch the titration curve that you would expect if 25.0 cm3 of 0.100 mol dm

–3

hydrochloric acid, HCl, is titrated with 40.0 cm3 of 0.100 mol dm

–3 ammonia solution,

NH3.

14

12

10

8

6

4

2

0

10 20 30 40

Volume of 0.100 mol dmammonia solution / cm3

–3

pH

(4)

(b) Using your answer to (a), select a suitable indicator for this titration. Put a tick in the

appropriate box in the table below.

Indicator pKInd ( )

thymol blue 1.7

bromocresol green 4.7

phenol red 7.9

phenolphthalein 9.3

(1)

(c) Suggest why there is no suitable indicator for the titration of ethanoic acid with ammonia.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 7 marks)

82. Methanoic acid and ethanol react together to form ethyl methanoate, HCOOC2H5, and water.

This reaction is reversible and can be allowed to reach equilibrium.

HCOOH(l) + C2H5OH(l) HCOOC2H5 (l) + H2O(l) ΔH = +45 kJ mol–1

(a) Draw the full structural formula of ethyl methanoate, showing all bonds.

(1)

(b) What type of organic compound is ethyl methanoate?

..................................................................................................................................... (1)

(c) In an experiment, 3.00 mol methanoic acid, HCOOH, and 6.25 mol ethanol, C2H5OH,

were mixed together. A small quantity of catalyst was added. The mixture was left for

several days in a water bath to reach equilibrium at constant temperature.

(i) Complete the table.

Number of moles in the reaction mixture

HCOOH C2H5OH HCOOC2H5 H2O

at start of

experiment 3.00 6.25 0.00 0.00

at equilibrium 0.50

(2)

(ii) Write an expression for the equilibrium constant, Kc, for the reaction.

(1)

(iii) Calculate Kc for the reaction at the temperature of the experiment. The total volume

of the equilibrium mixture was 485 cm3.

(2)

(iv) State and explain whether Kc for this reaction has units.

...........................................................................................................................

........................................................................................................................... (1)

(d) (i) The temperature of this equilibrium mixture is lowered.

Explain the effect of this on the value of the equilibrium constant and hence on the

yield of ethyl methanoate.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (4)

(ii) A student added more catalyst to the mixture.

State, giving a reason, what would happen to the composition of the equilibrium

mixture.

...........................................................................................................................

........................................................................................................................... (1)

(Total 13 marks)

83. A chemist has synthesised a compound W believed to be

HO CH CH CH C

Cl O

OH

(a) State and explain what you would see if W is reacted with:

(i) sodium carbonate solution

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) bromine water.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(b) W shows both types of stereoisomerism.

(i) How many stereoisomers of W are there? Briefly explain your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) Explain why W shows optical isomerism.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(c) Describe how you would show that W contains chlorine.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (5)

(Total 14 marks)

84. Two gases, A and B, react according to the equation

A(g) + 2B(g) → AB2(g)

A series of kinetics experiments performed at constant temperature gave the following results:

Experiment Initial concentration of

A /mol dm–3

Initial concentration of

B /mol dm–3

Initial rate

/mol dm–3

s–1

1 0.0500 0.100 1.00 ×10–4

2 0.0500 0.200 3.92 ×10–4

3 0.1000 0.100 1.95 ×10–4

(a) (i) Calculate, showing your working, the order of reaction with respect to A and to B.

(3)

(ii) Write the rate equation for the reaction.

........................................................................................................................... (1)

(iii) Calculate the rate constant, k, for the reaction in experiment 3, stating its units. (2)

(b) (i) Explain, in terms of collision theory, why the rate of reaction increases with an

increase in temperature.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(ii) Suggest, with an explanation, the least number of steps which is likely to exist in

the mechanism of the reaction between A and B.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(c) The variation of the rate constant, k, with change in temperature is given by the Arrhenius

equation:

ln k = ATR

Ea ln1

where A is a constant.

In a series of experiments performed at various temperatures T to determine the rate

constant, k, for the decomposition of a gas X, a graph of ln k against 1/T gave a straight

line of slope R

Ea:

–5

–6

–7

–8

–9

–10

–11

–12

ln k

0.0029 0.0030 0.0031 0.0032 0.0033 0.0034

1T

/ K –1

Use the graph to calculate the value of the activation energy, in kJ mol–1

, for the

decomposition of X. The value of the gas constant R = 8.31 J K–1

mol–1

.

(4)

(Total 15 marks)

85. When solid lead(II) sulphate is added to a solution of sodium iodide, the following equilibrium

is established:

PbSO4(s) + 2I– (aq) PbI2(s) + SO4

2– (aq)

The equilibrium constant, Kc, for this reaction may be found by adding an excess of solid

lead(II) sulphate to a known volume of a standard solution of sodium iodide. The mixture is left

to reach equilibrium at a constant temperature, T.

Ice-cold water is added to freeze the position of equilibrium and the mixture is then titrated with

standard silver nitrate solution.

In a typical experiment, excess lead(II) sulphate was added to 50.0 cm3 of 0.100 mol dm

–3

sodium iodide solution. The whole equilibrium mixture required 31.0 cm3 of 0.100 mol dm

–3

silver nitrate solution to react with the aqueous iodide ions.

The expression for Kc for this reaction is

Kc = 2

2

4

]I[

]SO[

(a) Why is it not necessary to know the mass of the lead(II) sulphate used in the experiment?

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(b) Give the ionic equation for the reaction between silver nitrate solution and aqueous iodide

ions to produce a precipitate of silver iodide, AgI.

..................................................................................................................................... (1)

(c) From the data given above, calculate the equilibrium amounts of the iodide and of the

sulphate ions in solution. Hence calculate the equilibrium concentration of these ions, and

the value of Kc for the reaction at temperature T, including the units, if any.

(8)

(Total 10 marks)

86. This question concerns the reactions of some compounds of nitrogen.

(a) The ammonium ion reacts with water and behaves as an acid.

NH4+(aq) + H2O(l) NH3(aq) + H3O

+(aq)

(i) Identify the TWO conjugate acid-base pairs in the spaces provided.

acid 1 ................................... base 1 ...................................

acid 2 ................................... base 2 ................................... (1)

(ii) Write the expression for the acid dissociation constant, Ka, of the ammonium ion.

(1)

(iii) A solution of ammonium chloride has a pH of 5.00 at 25°C.

Ka for the ammonium ion is 5.62 × 10–10

mol dm–3

at 25°C.

Calculate the concentration of this solution. State any assumptions you have made.

(4)

(iv) Use the following table and your answer from part (iii) to suggest a suitable

indicator for the titration of ammonia solution with hydrochloric acid. Justify your

answer.

Indicator pKIn

thymol blue 1.7

methyl red 5.1

phenolphthalein 9.3

...........................................................................................................................

........................................................................................................................... (2)

(b) Hydrogen cyanide is a weak acid in aqueous solution.

Write an equation to show why aqueous solutions of cyanide ions are alkaline.

..................................................................................................................................... (1)

(c) Hydrogen cyanide reacts with propanal as follows:

CH3CH2CHO + HCN → CH3CH2CH(OH)CN

Propanal is reacted with a solution of potassium cyanide, KCN, containing a little dilute

sulphuric acid.

(i) What type of reaction is this?

........................................................................................................................... (1)

(ii) Give the mechanism for the reaction.

(3)

(iii) It is important that the pH is neither too acidic nor too alkaline if a good yield of

the product is to be obtained. Explain why this is so.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(d) In an investigation of the kinetics of the nucleophilic substitution reaction between 1-

chloropropane and potassium cyanide in aqueous ethanolic solution, the reaction was

found to be first order with respect to 1-chloropropane and first order with respect to

cyanide ions.

(i) Give the rate equation for the reaction.

........................................................................................................................... (1)

(ii) Write a mechanism for the reaction that is consistent with this rate equation.

(3)

(Total 19 marks)

87. In the presence of hydrogen ions, H+, glucose, C6H12O6, can be oxidised by a solution of

potassium manganate(VII), KMnO4, which is purple in colour.

A series of experiments was carried out to determine the rate of reaction and the results are

shown below.

Experiment

Initial

concentration

of C6H12O6

/ mol dm–3

Initial

concentration

of KMnO4

/ mol dm–3

Initial

concentration

of H+

/ mol dm–3

Rate of

reaction

/ mol dm–3

s–1

1 1.0 0.01 0.5 2.0 × 10–5

2 1.0 0.005 0.5 1.0 × 10–5

3 0.5 0.005 0.5 1.0 × 10–5

4 1.0 0.02 1.0 8.0 × 10–5

(a) Describe how the rate of this reaction may have been measured.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(b) (i) Give the order of reaction with respect to each reactant. In the case of potassium

manganate(VII) and hydrogen ions explain how you arrived at your answer.

Glucose ................................................

Potassium manganate(VII) ...............................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Hydrogen ions ..................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(ii) Write the rate equation for this reaction.

........................................................................................................................... (1)

(iii) Using the data from experiment 1, calculate the rate constant for the reaction.

Include the units of the rate constant in your final answer.

(2)

(c) Additional experiments were carried out to investigate the effect of temperature on the

rate of reaction.

(i) Complete the missing data in the table below.

Temperature (T)

/ K

1/ temperature (1/T)

/ K–1

Rate constant ln (rate constant)

295 3.39 × 10–3

2.88 × 10–3

–5.85

305 3.28 × 10–3

1.01 × 10–2

–4.60

311 1.83 × 10–2

320 3.13 × 10–3

4.98 × 10–2

–3.00

333 3.00 × 10–3

2.02 × 10–1

–1.60

(1)

(ii) Plot a graph of ln (rate constant) on the vertical axis against 1/T on the horizontal

axis using the axes below.

(2)

(iii) Use the Arrhenius equation ln (rate) = T

1

R

E A

+ constant, together with your

graph to calculate a value of the activation energy, EA, for this reaction.

Show all steps in your working. Include units in your final answer, which should be

given to two significant figures.

[Gas constant, R = 8.31 J K–1

mol–1

]

(2)

(Total 13 marks)

88. Ammonia can be oxidised to form nitrogen(II) oxide and water according to the equation

4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g) ∆Hο = –905.6 kJ mol

–1.

In industry, the reaction is carried out at 1123 K with a platinum/rhodium catalyst.

The standard entropy of one mole of each substance in the equation, measured at 298 K, is

shown in the table below.

Substance Sο/ J mol

–1 K

–1

NH3 (g) +192.3

O2 (g) +205.0

NO (g) +210.7

H2O (g) +188.7

(a) (i) Use the values given to calculate the standard entropy change of the system,

∆Sοsystem, for this reaction. Include the sign and units in your final answer.

(2)

(ii) Is the sign for your value for ∆Sοsystem what you expected? Justify your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(iii) Calculate the entropy change of the surroundings, ∆Ssurroundings, at 1123 K for this

reaction. Include the sign and units in your final answer.

(2)

(iv) Calculate the total entropy change, ∆Stotal, for this reaction at 1123 K. Include the

sign and units in your final answer. You may assume that ∆Ssystem is unchanged at

high temperatures.

(1)

(v) What does your answer to (iv) tell you about the extent of the reaction at 1123 K?

Justify your answer.

...........................................................................................................................

........................................................................................................................... (1)

(vi) An energy profile was proposed to illustrate the effect of the catalyst on this

reaction. The proposal has two errors. Draw a corrected version on the axes below.

Progress of reaction

Energy

Uncatalysed

pathway

4NH3(g) +

5O (g)2

4NO(g) +

6H2O(g)

Catalysed

pathway

Proposal

4NH3(g) +

5O (g)2Energy

Corrected version

Progress of reaction (2)

(b) The oxidation of nitrogen(II) oxide leads to the following equilibrium

2NO(g) + O2(g) 2NO2(g)

The number of moles of each gas in a reaction mixture at equilibrium, at a pressure of

1.5atm, was found to be

Substance Number of moles

at equilibrium

NO (g) 0.025

O2 (g) 0.025

NO2 (g) 4.95

(i) Write the expression for the equilibrium constant, Kp, for this reaction.

(1)

(ii) Calculate the mole fraction of each gas and hence the value of the equilibrium

constant, Kp, for this mixture. Include units, if required, in your answer.

(4)

(iii) What does your answer to (ii) tell you about the position of the equilibrium?

Justify your answer.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(iv) If the total pressure of the reaction mixture was increased, describe what would

happen to the value of the equilibrium constant, Kp, and the partial pressure of

NO2(g). In each case justify your answer.

Equilibrium constant, Kp.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Partial pressure of NO2(g).

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 17 marks)

89. (a) The table below shows the acid dissociation constants, Ka, of three carboxylic acids.

Acid Structural formula Ka/ mol dm–3

Chloroethanoic CH2ClCO2H 1.3 × 10–3

Dichloroethanoic CHCl2CO2H 5.0 × 10–2

Trichloroethanoic CCl3CO2H 2.3 × 10–1

(i) Write an expression for the acid dissociation constant, Ka, of chloroethanoic acid.

(1)

(ii) Calculate the pH of a 0.0010 mol dm–3

solution of chloroethanoic acid, making the

usual assumptions.

(3)

(iii) Which acid would have the lowest pH at a concentration of 0.0010 mol dm–3

?

Use both the data and the structure of the acids to justify your answer. No further

calculation is required.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(b) Chloroethanoic acid, CH2ClCO2H, reacts with methanol, CH3OH, in the presence of a

sulphuric acid catalyst.

(i) Draw the displayed formula and give the name of the organic product formed.

Displayed Formula

Name ................................................................................................................. (3)

(ii) What name is given to the functional group formed in this organic product?

........................................................................................................................... (1)

(iii) What type of reagent is methanol in this reaction? Explain why it is able to behave

in this way and describe how it attacks the chloroethanoic acid.

You may find it helpful to draw a diagram.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(iv) How would you convert the organic product of the reaction between

chloroethanoic acid and methanol back into the original compounds?

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 15 marks)

90. This question is about ammonia, NH3, which is produced as shown in the following equation.

N2(g) + 3H2(g) 2NH3(g)

(a) Use oxidation numbers to explain why this is a redox reaction.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(b) (i) Use the average (mean) bond enthalpy data to calculate a value for the enthalpy

change for this reaction. You are reminded to show all your working.

Bond Average bond enthalpy

/ kJ mol–1

N≡N 944

H—H 436

N—H 388

(3)

(ii) The actual standard enthalpy change for this reaction is –92 kJ mol–1

. Explain why

the value you calculated in (b)(i) is not the same as this.

...........................................................................................................................

........................................................................................................................... (1)

(iii) At room temperature, a mixture of nitrogen and hydrogen is thermodynamically

unstable with respect to ammonia, but is kinetically stable.

Use the data in (b)(i) and (ii) to help you explain why this mixture is

thermodynamically unstable

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

kinetically stable

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(c) The manufacturer of ammonia would like to achieve a high rate of reaction and a high

equilibrium yield of product.

(i) State and explain, in terms of collision theory, TWO ways to increase the rate of

the reaction. An increase in pressure does not alter the rate in this process.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (6)

(ii) State and explain TWO ways to increase the equilibrium yield of ammonia.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (4)

(Total 19 marks)

91. Consider the following compounds.

H—C—C—C—C

H

H

H

H

H

H O—C—H

H

H

O

H—–C—–C—–C—–C

H

OH

H

H

H

H

H

O

C

H

H

H

OH

C—–C—–H

H

H

H

Compound X

Compound Y

Compound Z

C

(a) Name the functional groups present in the three compounds X, Y and Z.

Compound Functional groups present

X

Y

Z

(3)

(b) Compounds X, Y and Z are heated separately with alkaline ammoniacal silver nitrate

solution.

Draw the full structural formula, showing all bonds, of any organic product formed.

If a reaction does not occur, write ‘no reaction’.

Product from X

Product from Y

Product from Z

(3)

(c) Draw the formulae of the organic products formed by the reaction of

(i) X, CH3CH2CH2COOCH3, with aqueous sodium hydroxide solution.

(2)

(ii) Z, CH2(OH)CH2CH2CHO, with hydrogen cyanide.

(1)

(Total 9 marks)

92. (a) The equilibrium between hydrogen iodide, hydrogen and iodine was investigated by

sealing hydrogen iodide in glass tubes and heating the tubes at 698 K until equilibrium

was reached.

2HI(g) H2(g)+ I2(g) ΔH = + 9.4 kJ mol–1

The glass tubes were cooled rapidly and then opened in a solution of potassium iodide so

that the concentration of iodine at equilibrium could be determined by titration.

(i) Suggest why the reaction mixture was cooled rapidly.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) The expression for the equilibrium constant, Kc, for the above reaction is

Kc = 2

22

HI(g)][

)]g(I)][(H[ g

One of the tubes was found to contain iodine at a concentration of

5.0 × 10–4

mol dm–3

.

Calculate the equilibrium concentration of hydrogen iodide, in mol dm–3

.

The equilibrium constant, Kc, for the above reaction is 0.019 at 698 K.

(3)

(b) In a different experiment, 1.0 mol of hydrogen and 1.0 mol of iodine were allowed to

reach equilibrium at 698 K.

H2(g) + I2(g) 2HI(g)

At equilibrium, 80% of the hydrogen was converted to hydrogen iodide at a total pressure

of 1.1 atm.

(i) Write an expression for the equilibrium constant, Kp, for the reaction as shown.

(1)

(ii) Calculate the value of Kp.

(4)

(iii) Explain why, in this case, Kp has no units.

...........................................................................................................................

........................................................................................................................... (1)

(Total 11 marks)

93. This question is about propanoic acid, CH3CH2COOH.

(a) Propanoic acid is a weak acid which dissociates as follows

CH3CH2COOH(aq) + H2O(l) CH3CH2COO–(aq) + H3O

+(aq)

(i) In the above equation there are two conjugate acid-base pairs.

Identify them by completing the sentences below

Formula of one acid is ......................................................................................

The formula of its conjugate base is .................................................................

Formula of the other acid is ..............................................................................

The formula of its conjugate base is ................................................................. (2)

(ii) Propanoic acid is a weak acid. Explain what is meant by the term weak acid.

Weak

...........................................................................................................................

...........................................................................................................................

Acid

...........................................................................................................................

........................................................................................................................... (2)

(b) The acid dissociation constant, Ka, for propanoic acid is 1.30 × 10–5

mol dm–3

at 298 K.

(i) Write the expression for the acid dissociation constant, Ka, for propanoic acid.

(1)

(ii) A solution of propanoic acid has a pH of 3.44 at a temperature of 298 K.

Calculate the concentration, in mol dm–3

, of the propanoic acid solution. Show

clearly two assumptions you have made.

Calculation:

Assumptions:

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (5)

(c) A mixture of sodium propanoate and propanoic acid acts as a buffer solution.

(i) What is meant by a buffer solution?

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) Calculate the pH of a buffer solution made by mixing 100 cm3 of 0.0100 mol dm

–3

propanoic acid solution with 300 cm3 of 0.00500 mol dm

–3 sodium propanoate

solution at 298 K.

[Ka for propanoic acid is 1.30 × 10–5

mol dm–3

at 298 K]

(3)

(Total 15 marks)

94. Name the following organic compound

HCHO

............................................................................................................................................... (Total 1 mark)

95. (a) Draw the displayed formula of a branched chain ketone containing five carbon atoms.

(2)

(b) Give the systematic name for this ketone.

..................................................................................................................................... (1)

(c) What is the molecular formula of the alcohol this ketone could be made from?

..................................................................................................................................... (1)

(d) An alcohol can be converted into a ketone by oxidation with sodium dichromate(VI) and

sulphuric acid.

Explain why refluxing the mixture first, rather than immediately distilling the product

over from the beginning, results in a higher yield of the ketone.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(Total 5 marks)

96. This question is about the reaction between barium hydroxide and ammonium chloride:

Ba(OH)2(s) + 2NH4Cl(s) → BaCl2.2H2O(s) + 2NH3(g) ΔH = +21.2 kJ mol–1

(a) Standard entropies of the reactants and products are shown below:

Substance Standard entropy, S

ο

/ J mol–1

K–1

Ba(OH)2(s) + 99.7

NH4Cl(s) + 94.6

BaCl2.2H2O(s) +202.9

NH3(g) +192.3

Calculate the standard entropy change for the system, ΔSοsystem, for this reaction.

Include a sign and units in your answer.

(2)

(b) Calculate the entropy change for the surroundings, ΔSοsurroundings, at 298 K. Give your

answer to 3 significant figures and include a sign and units in your answer.

(2)

(c) (i) Use your answers to (a) and (b) to explain why this reaction is spontaneous at 298

K.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(ii) When these two solids are mixed together in a beaker, no reaction is observed.

What explanation can be given for this, in view of the fact that the process is

spontaneous?

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(iii) Apart from heating the mixture, suggest what might be done to encourage the

reaction to take place. Explain why your suggestion is likely to work.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 8 marks)

97. The principal reaction occurring when 2-bromo-2-methylpropane reacts with aqueous sodium

hydroxide is as follows:

CH 3 3 3C(CH )CH + NaOH CH C(CH )CH3 3 3 + NaBr

Br OH

Several experiments were carried out in order to follow the kinetics of this alkaline hydrolysis.

A few drops of phenolphthalein were added to a sample of sodium hydroxide, and, after the

addition of a measured amount of 2-bromo-2-methylpropane, the mixture was vigorously

shaken and a clock was immediately started. The time was taken when the pink colour due to

the indicator disappeared.

This experiment was repeated twice using different concentrations of the two reactants.

All experiments were carried out at the same temperature.

The results are shown in the table below.

Experiment 2-bromo-2-methylpropane

/ mol dm–3

Sodium hydroxide

/ mol dm–3

Time /s

A 0.011 8.0 × 10–4

33

B 0.022 8.0 × 10–4

16

C 0.022 1.2 × 10–3

24

(a) (i) Identify the attacking species responsible for this alkaline hydrolysis.

........................................................................................................................... (1)

(ii) Assuming that the final concentration of sodium hydroxide is zero, calculate the

average rates of reaction in mol dm–3

s–1

for experiments A and B.

A ................. mol dm–3

s–1

B ................. mol dm–3

s–1

(2)

(iii) Deduce the order of reaction with respect to 2-bromo-2-methylpropane. Justify

your answer.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(iv) By comparing the average rates of reaction between experiments B and C, deduce

the order of reaction with respect to sodium hydroxide.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(v) Write the rate equation for the reaction.

Rate = (1)

(vi) From your rate equation, suggest how this reaction proceeds by giving a possible

mechanism.

(3)

(b) Explain briefly why 1-bromobutane, an isomer of 2-bromo-2-methylpropane, reacts by a

different mechanism when it is hydrolysed.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 12 marks)

98. The equation below shows the equilibrium existing between nitrogen, oxygen and nitrogen

monoxide.

N2(g) + O2(g) 2NO(g)

The equilibrium constant, Kp, at 298 K is 5.0 ×10–31

(a) (i) Write an expression for the equilibrium constant, Kp, in terms of the partial

pressures of the three gases.

(1)

(ii) Why does the value for Kp have no units?

...........................................................................................................................

........................................................................................................................... (1)

(b) An equilibrium mixture of these three gases was found to contain nitrogen, at a partial

pressure of 0.87 atm, and oxygen, at a partial pressure of 0.23 atm.

(i) Calculate the partial pressure exerted by the nitrogen monoxide.

(2)

(ii) Deduce the value of the total pressure of the equilibrium mixture of gases.

(1)

(iii) Assuming that the total pressure on the mixture of gases is doubled, what, if any,

would be the effect on the

• partial pressure of nitrogen monoxide

.....................................................................................................................................

.

.....................................................................................................................................

.

• equilibrium constant, Kp?

.....................................................................................................................................

.

.....................................................................................................................................

. (2)

(c) Inside a car engine, air (a mixture of nitrogen and oxygen) is drawn in and, under the high

temperatures operating, the value of Kp increases dramatically.

This increase is also accompanied by an increase in the value of ΔStotal. Typical values of

Kp and ΔStotal are shown in the table below.

Temperature / K Kp ΔStotal / J mol–1

K–1

298 5.0 × 10–31

–580

1500 1.0 × 10–5

– 96

Although the value of ΔSsystem is unlikely to alter very much, the value for ΔSsurroundings

will change significantly.

(i) At a temperature of 1500 K, ΔStotal is negative.

Does this mean that the reaction between nitrogen and oxygen cannot occur at this

temperature? Explain your reasoning.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(ii) Why is the value for ΔSsystem for this equilibrium approximately constant when the

temperature rises above 298 K?

...........................................................................................................................

........................................................................................................................... (1)

(iii) What is the sign of ΔSsurroundings for an endothermic reaction? Justify your answer.

...........................................................................................................................

........................................................................................................................... (1)

(iv) Explain why an endothermic reaction results in an increase in the value of ΔStotal as

the temperature increases.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(d) A student used the value for Kp at 1500 K to calculate the partial pressure of nitrogen

monoxide inside a working car engine.

Why might the actual partial pressure be lower than the calculated answer?

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(Total 12 marks)

99. Calculate the pH of the buffer solution formed by mixing 10 cm3 of aqueous benzoic acid of

concentration 0.010 mol dm–3

with 40 cm3 of aqueous sodium benzoate of concentration 0.020

mol dm–3

.

For benzoic acid, the acid dissociation constant, Ka, is 6.3 × 10–5

mol dm–3

.

You may find it helpful to use the relationship pH = – log Ka – [base]

acid][log

(Total 3 marks)

100. Compound V, the structure of which is shown below, is found in human sweat.

C C

HCH3

CCH3 CH2 CH2

OH

O

Compound V

(a) Compound V contains two functional groups.

Identify both functional groups and state a chemical test for each. The result of each test

should also be included in your answer.

One functional group in V ...........................................................................................

Test and result .............................................................................................................

.....................................................................................................................................

.....................................................................................................................................

The other functional group in V .................................................................................

Test and result .............................................................................................................

.....................................................................................................................................

..................................................................................................................................... (4)

(b) Compound V can be converted into two carbonyl compounds W and X, shown below.

C C

OH

O OH

W

CH

CH CH CH

3

3 2 2 C

O

X

(i) Which of the compounds W or X would react when warmed with Fehling‘s

solution to give a red precipitate? Justify your answer.

...........................................................................................................................

........................................................................................................................... (1)

(ii) Compound W can be reduced in two steps to compound Y of molecular formula

C2H6O2.

Identify Y.

........................................................................................................................... (1)

(iii) Compound W can be oxidised to compound Z of molecular formula C2H2O4.

Identify Z.

........................................................................................................................... (1)

(c) The compounds Y and Z react together under suitable conditions to form a polymer.

(i) Draw the structural formula of the repeating unit for the polymer formed.

(2)

(ii) What type of polymerisation reaction occurs between compounds Y and Z?

........................................................................................................................... (1)

(Total 10 marks)

101. Consider the equilibrium

N2O4(g) 2NO2(g) ΔH = +58 kJ mol–1

(a) Write the expression for the equilibrium constant, Kp, for the above reaction.

(1)

(b) (i) An equilibrium mixture contains a mole fraction of dinitrogen tetroxide,

N2O4 = 0.20, and nitrogen dioxide, NO2 = 0.80. The total pressure of this mixture

is 1.1 atm.

Calculate Kp at this temperature, stating its units.

(3)

(ii) Calculate the total pressure required to reduce the mole fraction of N2O4 to 0.10.

(3)

(c) (i) What is the effect on Kp, if any, of raising the temperature?

........................................................................................................................... (1)

(ii) Use your answer to (c)(i) to explain the effect of increasing the temperature on the

position of equilibrium.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 10 marks)

102. (i) Use the data below to calculate a value for the enthalpy change of solution, ΔHsolution, for

silver fluoride.

Value

/kJ mol–1

lattice energy of AgF (s) –958

enthalpy of hydration of Ag+ (g) –464

enthalpy of hydration of F– (g) –506

(2)

(ii) Use your answer to part (c)(i) to suggest whether you would expect silver fluoride, AgF,

to be soluble or insoluble in water at room temperature.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 4 marks)

103. (a) The values of the ionic product of water, Kw, at two different temperatures are shown in

the table below.

Temperature /°C Kw

/ mol2 dm

–6

25 1.00 × 10–14

50 5.48 × 10–14

(i) Write an equation to represent the ionisation of water.

........................................................................................................................... (1)

(ii) Write the expression for Kw.

........................................................................................................................... (1)

(iii) Define the term pH.

...........................................................................................................................

........................................................................................................................... (1)

(iv) Calculate the pH of pure water at 50 °C.

(2)

(v) Explain why pure water at 50 °C is neutral despite the fact that its pH is not 7.

...........................................................................................................................

........................................................................................................................... (1)

(b) The pH curve shown below was obtained when a 0.100 mol dm–3

solution of sodium

hydroxide was added to 25.0 cm3 of a 0.100 mol dm

–3 solution of ethanoic acid.

14

12

10

8

6

4

2

00 10 20 30 40

pH

Volume 0.100 mol dm NaOH / cm3–3

(i) What volume of sodium hydroxide solution is required to neutralise half of the

ethanoic acid in this reaction?

Volume added = ..............................................................cm3

(1)

(ii) Use the graph to determine the pH when the volume of sodium hydroxide you have

stated in part (i) has been added.

pH is ..................................................................................... (1)

(iii) Write an expression for the acid dissociation constant, Ka, of ethanoic acid,

CH3COOH.

(1)

(iv) Use your answers to parts (ii) and (iii) to determine the value of Ka for ethanoic

acid at the temperature of the titration. Give your answer to two significant figures.

(2)

(c) Phenolphthalein is a suitable indicator for a titration between ethanoic acid and sodium

hydroxide solutions whereas methyl orange is not a suitable indicator.

Explain why this is so.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 13 marks)

104. Ethanal, CH3CHO, can be converted into 2-hydroxypropanoic acid, CH3CH(OH)COOH.

State the reagents and conditions needed for each step in this synthesis.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

............................................................................................................................................... (Total 4 marks)

105. This question concerns the reaction between nitrogen monoxide and oxygen:

2NO(g) + O2(g) → 2NO2(g)

(a) In a series of experiments designed to find the rate equation for this reaction, the

following data were obtained. In each experiment the partial pressure of oxygen was the

same.

30

0

25

20

15

10

5

00.05 0.1 0.15 0.2

Square of the partial pressure of NO/atm 2

Initial rate /atm s –1

(i) What is the order of reaction with respect to nitrogen monoxide?

Justify your answer.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) A new series of readings is taken with the partial pressure of oxygen doubled.

The gradient of the line doubles.

State, with a reason, the order of reaction with respect to oxygen.

...........................................................................................................................

........................................................................................................................... (1)

(iii) Hence write the rate equation for the reaction.

........................................................................................................................... (1)

(iv) State the units of the rate constant.

........................................................................................................................... (1)

(b) The rate of the decomposition of nitrous oxide

2N2O(g) → 2N2(g) + O2(g)

has been studied at different temperatures. The rate constant k was determined at each

temperature.

The relationship between the rate constant and the temperature T is given by the

Arrhenius equation:

TR

EAk

1lnln a

where Ea is the activation energy for the reaction, R is the gas constant, and k is the rate

constant at temperature T.

(i) Given values of k at different temperatures T, what graph would you plot and how

would you use it to determine the activation energy?

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) A plot of the data gave a straight line with gradient – 2.95 × 104 K

–1.

Find the activation energy for the reaction, in kJ mol–1, to three significant

figures.

[The value of R is 8.314 J K–1

mol–1

]

(2)

(iii) What is the oxidation number of nitrogen in nitrous oxide, N2O?

Put a cross ( ) in the box of the correct answer. If you change your mind about an

answer, put a line through the box ( ) and then mark your new answer with a

cross ( ).

A +2

B +1

C –1

D –2

(1)

(Total 10 marks)

106. Cyanide ions react with 2-bromo-2-methylpropane in the following way:

(CH3)3CBr + CN– → (CH3)3CCN + Br

–

The rate equation for this reaction is

rate = k[(CH3)3CBr]

(i) What information does this rate equation give about the mechanism of this reaction?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(ii) Give the mechanism for this reaction consistent with the rate equation.

(3)

(Total 5 marks)

107. The enthalpy change for some reactions cannot be determined directly.

One such reaction is the thermal decomposition of potassium hydrogencarbonate, which in a

closed system at 200 °C is an equilibrium reaction.

2KHCO3 K2CO3 + H2O + CO2

However, by determining the enthalpy change for the neutralisation of the two potassium salts

with hydrochloric acid, ΔH for the reaction above can be found. The equations for the

neutralisation reactions are:

K2CO3 + 2HCl → 2KCl + H2O + CO2 ΔH1

KHCO3 + HCl → KCl + H2O + CO2 ΔH2

ΔH1 and ΔH2 for the neutralisation reactions were determined as follows:

• 30 cm3 of 2 mol dm

–3 hydrochloric acid (an excess) was placed in a polystyrene cup, and

its temperature measured to the nearest 0.1°C.

• A weighed quantity of the potassium salt (either the carbonate or the hydrogencarbonate)

was added to the acid with rapid stirring, and the temperature measured again when the

reaction was complete.

For the neutralisation using potassium carbonate, the results were as follows:

Amount of potassium carbonate used = 0.0187 mol

Initial temperature = 23.7 °C

Final temperature = 30.1 °C

(a) State Hess‘s Law.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(b) Use the data for the neutralisation of potassium carbonate to calculate the value of ΔH1 to

two significant figures. Remember to include a sign and units in your answer.

[Assume that the heat capacity of the solution is 4.18 J g–1

°C–1

, and that it has a mass of

30 g.]

(3)

(c) (i) Show how the two equations for the neutralisation reactions and their ΔH values

can be combined to find a value of ΔH for the thermal decomposition of potassium

hydrogencarbonate.

Calculate this enthalpy change using your value for ΔH1 from part (b), given that

ΔH2 = + 29.3 kJ mol–1

.

(3)

(ii) Explain why you would need to include the enthalpy of vaporisation of H2O(l), in

order to obtain an accurate value of the enthalpy of decomposition of potassium

hydrogencarbonate.

2KHCO3(s) K2CO3(s) + H2O(g) + CO2(g)

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(d) State and explain the effect of a decrease in temperature on the value of the equilibrium

constant for the decomposition reaction and hence on the composition of the equilibrium

mixture.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 10 marks)

108. (i) Draw the shape of a water molecule. Justify your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(ii) Water has intermolecular hydrogen bonds, but hydrogen sulphide, H2S, does not.

Explain how these arise in water and why they do not occur in hydrogen sulphide.

Give ONE resulting difference in physical properties of water and hydrogen sulphide.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 5 marks)

109. (a) Name the homologous series to which the compound CH3CH2CHO belongs.

..................................................................................................................................... (1)

(b) Describe what you would see if a sample of CH3CH2CHO was warmed with Benedict‘s

solution.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 3 marks)

110. This question is about the reaction of iodine with propanone.

CH3COCH3(aq) + I2(aq) → CH3COCH2I(aq) + H+(aq) + I

–(aq)

(a) Suggest, in outline, THREE different methods for following the rate of this reaction.

State which of the reactants or products could be measured by each method you choose.

Method 1

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Method 2

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Method 3

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(b) The reaction is extremely slow at room temperature in the absence of H+ ions as a

catalyst.

Suggest how you would quench the reaction before carrying out a titration method to

determine the concentration of iodine at different times.

Justify your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(c) A series of experiments was carried out, varying the concentrations of the reactants and

the catalyst. The following results were obtained.

Experiment [CH3COCH3]

/mol dm–3

[I2]

/mol dm–3

[H+]

/mol dm–3

Initial rate

/mol dm–3

s–1

1 1.00 0.010 0.10 2.8 ×10–6

2 1.00 0.010 0.20 5.6 ×10–6

3 1.50 0.010 0.20 8.4 ×10–6

4 1.50 0.020 0.10 4.2 ×10–6

The reaction is first order with respect to hydrogen ions, H+.

(i) Deduce the order of the reaction with respect to propanone, CH3COCH3. Justify

your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(ii) Deduce the order of the reaction with respect to iodine, I2.

........................................................................................................................... (1)

(iii) Hence give the rate equation for this reaction.

(1)

(iv) Which species are involved in the rate-determining step?

...........................................................................................................................

........................................................................................................................... (1)

(v) Suggest an equation for the reaction between the species in the rate-determining

step.

Explain why this step is likely to take place.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 13 marks)

111. One of the alarm pheromones for ants, compound Q, has the molecular formula C6H10O.

(a) State what can be deduced about compound Q from each of the following pieces of

information.

(i) Q, C6H10O, is a non-cyclic organic compound. When saturated it would contain 14

hydrogen atoms.

...........................................................................................................................

........................................................................................................................... (1)

(ii) Compound Q does not react with sodium.

...........................................................................................................................

........................................................................................................................... (1)

(iii) One mole of compound Q reacts with one mole of bromine molecules, Br2, in the

absence of sunlight.

...........................................................................................................................

........................................................................................................................... (1)

(iv) Compound Q gives a yellow precipitate with Brady‘s reagent, 2,4-

dinitrophenylhydrazine.

........................................................................................................................... (1)

(v) When compound Q is warmed with Benedict‘s solution, a red precipitate is

formed.

........................................................................................................................... (1)

(vi) Compound Q exists in the trans form.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(vii) Given that compound Q is a straight chain molecule with the two functional groups

next to one another, give the displayed formula of Q.

(2)

(b) (i) Compound Q, C6H10O, can be converted into C6H14O in two steps.

Give the reagent and any catalyst needed for each step.

Step 1 ................................................................................................................

...........................................................................................................................

Step 2 ................................................................................................................

........................................................................................................................... (2)

(ii) Name the functional group which would now be present?

........................................................................................................................... (1)

(Total 11 marks)

112. Phosphorus(V) chloride dissociates as follows:

PCl5(s) PCl3(l) + Cl2(g) ∆Hο = + 123.8 kJ mol

–1

Substance Standard entropy, S

ο

/ J mol–1

K–1

PCl5(s) + 166.5

PCl3(l) + 217.1

Cl2(g) + 165.0

(a) (i) Explain why the entropy of solid phosphorus(V) chloride, PCl5, is smaller than the

entropy of liquid phosphorus(III) chloride, PCl3?

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(ii) Calculate ∆Sοsystem for the forward reaction. Include a sign in your answer.

(1)

(iii) Is the sign of ∆Sοsystem as you would expect? Fully justify your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(b) Calculate ∆Sοsurroundings for the forward reaction at 298 K. Include a sign and units in your

answer.

(2)

(c) (i) Use your answers to calculate ∆Sοtotal for the forward reaction at 298 K. Include a

sign in your answer.

(1)

(ii) Comment on the position of equilibrium at 298 K.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(d) In an experiment to investigate this equilibrium, 41.7 g of phosphorus(V) chloride (molar

mass 208.5 g mol–1

) was heated in a closed vessel at 150 °C until equilibrium was

established. The final pressure was found to be 4.32 atm and 0.15 moles of

phosphorus(V) chloride remained. At this temperature all of the reactants and products

are gaseous.

(i) Give the expression for the equilibrium constant, Kp, and its units at this

temperature.

(2)

(ii) Complete the table

Substance Moles at start Moles at equilibrium Partial pressure at

equilibrium, peq

/atm

PCl5(g) 0.15

PCl3(g) 0

Cl2(g) 0

Total number of moles at equilibrium

(3)

(iii) Calculate Kp.

(1)

(iv) How would you expect the value of Kp to change, if at all, if the following changes

were made? Justify each of your answers.

A Only 20.85 g of phosphorus(V) chloride had been used.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

B The temperature had been increased to 250 °C.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 16 marks)

113. Human blood plasma is a buffer solution. It partly owes its buffer properties to carbon dioxide,

produced by respiration, dissolving in the blood for transportation to the lungs.

Carbon dioxide dissolves in water establishing the equilibrium

CO2(aq) + H2O(l) H+(aq) + HCO3

–(aq)

(a) (i) Write the expression for Ka for this equilibrium and give its units.

Units ........................ (2)

(ii) What is the relationship between pKa and Ka?

(1)

(b) Explain what is meant by a buffer solution.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(c) HCO3–(aq) can act as an acid or a base.

CO2(aq) + H2O(l) H+(aq) + HCO3

–(aq)

In this equilibrium, decide whether HCO3–(aq) is acting as an acid or as a base. Give the

reason for your decision.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(d) A sprinter had the pH and total carbonate concentration, [CO2 + HCO3–], of his blood

plasma measured immediately before and after a race. The following results were

obtained.

pH

Total carbonate concentration, [CO2 + HCO3–]

/ mol dm–3

Before race 7.4 2.52 × 10–2

After race 7.3 1.98 × 10–2

The pH of a buffer solution is given by the equation

[base]

acid][logppH a K

For this equilibrium pKa is 6.5.

(i) Use this information, together with the data in the table, to calculate [base]

acid][ before

the race.

(2)

(ii) The concentration of HCO3– is 0.0224 mol dm

–3. Calculate the concentration of

CO2 before the race.

(1)

(iii) Use your results from (d)(i) and (ii) to complete the table below which will allow

you to compare the results before and after the race.

[base]

acid][

[HCO3–]

/ mol dm–3

[CO2]

/ mol dm–3

Before race 0.0224

After race 0.158 0.0171 0.00270

Two hypotheses have been proposed to explain why vigorous exercise results in an

increase in blood plasma acidity (from 7.4 to 7.3).

Greater muscle activity during a race requires:

either

Hypothesis I the combustion of larger quantities of glucose, resulting in an

increase in dissolved carbon dioxide and hence an increase in

acidity.

or

Hypothesis II partial oxidation of glucose to lactic acid and hence an increase in

acidity.

State, giving your reasons, which hypothesis is favoured by the data and your

calculations.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(Total 11 marks)

114. The drug ibuprofen can be synthesised from benzene by the route shown below.

H—C—CH

CH

3

2

CH3

H—C—CH

CH

3

2

CH3

H—C—OH

CH3

H—C—CH

CH

CH

3

2

3

C O

CH3

Step A Step B Step C

CO/Pd

catalyst

H—C—CH

CH

3

2

CH3

H—C—CO H2

CH3

Ibuprofen

(a) Name the type and mechanism of the reaction in Step A, and suggest a suitable reagent

and catalyst.

Type and mechanism ..................................................................................................

Name of the reagent for Step A ..................................................................................

Catalyst ....................................................................................................................... (3)

(b) Step C is a reduction.

Give ONE reason why lithium tetrahydridoaluminate, LiAlH4, is preferred to hydrogen as

a reducing agent in this reaction.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(c) A sample of the final product was analysed by combustion. 1.00 g was burnt in oxygen. It

produced 2.78 g carbon dioxide and 0.786 g water.

State the molecular formula of ibuprofen and show that these results are consistent with

it.

(4)

(d) Ibuprofen can be analysed by instrumental methods. The infrared spectra of ibuprofen

and two other drugs, aspirin and paracetamol, not necessarily in that order, are shown

opposite.

Ibuprofen has the formula

Aspirin has the formula

Paracetamol has the formula

H—C—CH

CH

3

2

CH3

H—C—CO H2

CH3

—O—C

O

CH

OH

3

H—N—C

O

CH

CO H

3

2

(i) Explain, referring to the structure of each molecule, why infrared spectroscopy is

not a good technique to distinguish aspirin from ibuprofen.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(ii) Deduce which of X, Y or Z is the infrared spectrum of paracetamol, giving a piece

of evidence from the spectrum you select.

100

50

04000 3000 1500 10002000

Wavenumber/cm–1

Tra

nsm

itta

nce

(%

)

100

50

04000 3000 1500 10002000

Wavenumber/cm–1

Tra

nsm

itta

nce

(%

)

100

50

04000 3000 1500 10002000

Wavenumber/cm–1

Tra

nsm

itta

nce

(%

)

Spectrum X

Spectrum Z

Spectrum Y

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(iii) Ibuprofen and aspirin can be distinguished using their mass spectra.

A line at mass/charge ratio 57 occurs only in the mass spectrum of ibuprofen.

Give the formula of the ion which produces this line.

...........................................................................................................................

Suggest the mass/charge ratio of one line which occurs in the mass spectrum of

aspirin but not ibuprofen, and the formula of the species which produces it.

...........................................................................................................................

........................................................................................................................... (3)

(Total 14 marks)

115. This question involves the following techniques which can be used to follow chemical reactions

in order to investigate their kinetics.

A collecting and measuring the volume of a gas

B colorimetry

C measuring the electrical conductivity

D titration with standard acid solution

Select, from A to D, the technique most appropriate to investigate:

(a) the hydrolysis of 1-bromobutane using hydroxide ions

C4H9Br(l) + OH–(aq) C4H9OH(l) + Br

–(aq)

A

B

C

D (1)

(b) the decomposition of the benzenediazonium ion

C6H5N2+(aq) + H2O(l) C6H5OH(aq) + N2(g) + H

+(aq)

A

B

C

D (1)

(c) the reaction of acidified potassium manganate(VII) with propan-2-ol to give propanone

and manganese(II) sulfate.

A

B

C

D (1)

(d) the catalytic decomposition of hydrogen peroxide.

A

B

C

D (1)

(Total 4 mark)

116. 1,2-dibromoethane reacts with potassium iodide dissolved in methanol according to the

equation:

C2H4Br2 + 2KI C2H4 + 2KBr + I2

The rate equation for this reaction is

A rate = k[KI]2[C2H4Br2]

B rate = k[KI]2

C rate = k[C2H4Br2]

D not possible to deduce from this information (Total 1 mark)

117. For the reaction between sodium bromate(V) and sodium bromide in acidic solution, the rate

equation is:

Rate = k[BrO3–][Br

–][H

+]2

When the concentrations of all three reactants are doubled, the rate will increase by a factor of

A 4

B 6

C 8

D 16 (Total 1 mark)

118. This question refers to the following reaction at 298 K:

N2O4(g) 2NO2(g) H = + 57.2 kJ mol–1

S

/J mol–1

K–1

N2O4(g) 304.2

NO2(g) 240.0

(a) Calculate Ssystem, in J mol–1

K–1

, for this reaction.

A –175.8

B +175.8

C –64.2

D +64.2 (1)

(b) Calculate Ssurroundings, in J mol–1

K–1

, for this reaction at 298 K.

A –192

B +192

C –0.192

D +0.192 (1)

(Total 2 marks)

119. For the equilibrium,

N2(g) + 3H2(g) 2NH3(g)

Which is the correct expression for Kp?

A 3

22

23

g)](g)][H(N[

)]g(NH[

B g)(NH

g)(Hg)(N

3

22

P

PP

C g)(H

3g)(N

g)(NH2

22

3

PP

P

D g)(NH

2

g)(H3

g)(N

3

22

P

PP

(Total 1 mark)

120. The expression for Kc for the equilibrium 2SO2(g) + O2(g) 2SO3(g) is

Kc = g)](O[g)](SO[

g)]([SO

22

2

23

What are the units of Kc in this equilibrium expression?

A mol dm–3

B mol2 dm

–6

C dm3 mol

–1

D atm–1

(Total 1 mark)

121. For the equilibrium

2NO2(g) N2O4(g) H = –57.2 kJ mol–1

which one of the following changes would result in a different value of the equilibrium

constant?

A an increase in temperature

B a decrease in pressure

C an increase in pressure

D an increase in the concentration of NO2(g)

(Total 1 mark)

122. Solutions of concentration 0.1 mol dm–3

of iron(II) ions and silver(I) ions were mixed at room

temperature and allowed to reach equilibrium.

Fe2+

(aq) + Ag+(aq) Fe

3+(aq) + Ag(s)

Which one of the following statements is true?

A as the equilibrium position was approached, the forward reaction became slower until it

stopped.

B at the equilibrium position, no more Ag(s) reacted with Fe3+

(aq).

C at the equilibrium position, the rate of the forward reaction equalled the rate of the

backward reaction.

D no Fe3+

(aq) reacted with Ag(s) until the equilibrium position was reached. (Total 1 mark)

123. This question concerns four solutions, A to D. They were prepared by mixing equal volumes of

0.2 mol dm–3

solutions of two different substances. The substances were

A HCl(aq) and NaOH(aq)

B HCl(aq) and NaCl(aq)

C NH3(aq) and NH4Cl(aq)

D CH3COOH(aq) and CH3CO2Na(aq)

Select, from A to D, the mixture which would:

(a) have the lowest concentration of hydrogen ions

A

B

C

D (1)

(b) act as a buffer of pH about 5

A

B

C

D (1)

(c) have a chloride ion concentration of 0.2 mol dm–3

.

A

B

C

D (1)

(Total 3 marks)

124. This question concerns the titration of a solution of sodium hydroxide with a solution of

hydrochloric acid. As the titration proceeds the pH of the mixture changes.

(a) What was the pH when 24.95 cm3 of 1.00 mol dm

–3 NaOH(aq) had been added to 25 cm

3

of 1.00 mol dm–3

HCl(aq)?

A 3

B 6

C 8

D 11 (1)

(b) What was the pH when 25.05 cm3 of 1.00 mol dm

–3 NaOH(aq) had been added to 25 cm

3

of 1.00 mol dm–3

HCl(aq)?

A 3

B 6

C 8

D 11 (1)

(c) Which one of the following indicators would be most suitable to use to determine the end

point of this titration?

pH range

A methyl violet 0–1.6

B universal indicator 3–11

C thymolphthalein 8.3–10.6

D alizarin yellow R 10.1–13.0 (1)

(Total 3 marks)

125. Which one of the following organic compounds does not exist?

A an ester which is a structural isomer of a carboxylic acid C3H6O2

B a carboxylic acid which is a structural isomer of an ester C2H4O2

C an aldehyde which is a structural isomer of a ketone C3H6O

D a ketone which is a structural isomer of an aldehyde C2H4O

(Total 1 mark)

126. This question concerns a proposed two-stage synthetic route to prepare butanamide,

CH3CH2CH2CONH2

NH3

Carboxylic acid Acyl chloride butanamide

(a) A suitable starting material for this preparation would have the formula

A CH3CH2CH2COH

B CH3CH2CH2CH2COOH

C CH3CH2CH2COOH

D CH3CH2CH2CH2OOH

(1)

(b) Each stage in the sequence produced a 50% yield of required product. What is the

minimum number of moles of the carboxylic acid which should be used in order to

produce one mole of butanamide?

A 0.25

B 2.00

C 2.50

D 4.00 (1)

(c) Which of the following reagents is needed to convert the carboxylic acid into the acyl

chloride?

A chlorine

B phosphorus(V) chloride

C hydrogen chloride

D ethanoyl chloride (1)

(Total 3 marks)

127. This question concerns the following compounds containing four carbon atoms.

A Butanoic acid, CH3CH2CH2COOH

B Butanone, CH3COCH2CH3

C Propyl methanoate, HCOOCH2CH2CH3

D Butanoyl chloride, CH3CH2CH2COCl

Select, from A to D, the compound that

(a) can be made by the oxidation of a primary alcohol.

A

B

C

D (1)

(b) would be expected to react most rapidly with ethanol.

A

B

C

D (1)

(c) would have 4 different chemical shifts in its nmr spectrum and a broad absorption

between 2500–3300 cm–1

in its infrared spectrum.

A

B

C

D (1)

(Total 3 marks)

128. This question concerns the nucleophilic addition reaction between a carbonyl compound and

hydrogen cyanide, HCN.

(a) Which one of the following carbonyl compounds would produce a racemic mixture?

A CH3COCH3

B C2H5CHO

C HCHO

D C2H5COC2H5

(1)

(b) Which of the following best represents the first step of the mechanism for this reaction

with an aldehyde?

A

B

C

D

R

C

H

R

C O+ –

H

R

C

H

R

C

H CN

O–

(:C

C

H

R

C

H CN

O–

(:C

C

H

R

C+

H

OH

H C N + –CN

O

O

O

O

N:)

R

R

N:)

–

–

(1)

(Total 2 marks)

129. This question concerns the formation of a polymer.

(a) Which one of the following is a possible formula of the repeat unit of a polymer formed

from ethane-1,2-diol and benzene-1,4-dicarboxylic acid.

A

B

C

D

C

O

O

C O CH2 2CH O

O CH2 CH2 O C C

O

O

OH

C O CH2 2CH O

H

C

OH

O CH2 2CH O C C

HO H

OHH (1)

(b) What type of reaction is this?

A addition

B condensation

C dehydration

D neutralisation (1)

(Total 2 marks)

130. This question is about the pineapple flavouring used in sweets. It is an ester with the formula

C3H7COOCH3, which can be broken down into butanoic acid and methanol when mixed with

hydrochloric acid.

The following equilibrium is set up:

C3H7COOCH3(l) + H2O(l) C3H7COOH(l) + CH3OH(l)

(a) Give the name of this ester.

..................................................................................................................................... (1)

(b) Why does the ester have a comparatively low boiling point compared to the other three

substances in the equation?

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (1)

(c) What is the name given to this type of reaction?

..................................................................................................................................... (1)

(d) Suggest the reasons why manufacturers choose to use the chemically manufactured

pineapple flavouring rather than the natural product and why consumers might prefer to

choose the natural product.

.....................................................................................................................................

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..................................................................................................................................... (4)

(e) In an experiment, 10.2 g (0.10 mol) of the ester was mixed with 18 cm3 of 1.0 mol dm

–3

hydrochloric acid and left until equilibrium had been reached. The hydrochloric acid acts

as a catalyst and contains 18 g (1 mol) of water. At equilibrium, 4.4 g of butanoic acid

was found to be present.

Molar mass of butanoic acid = 88 g; assume the total volume at equilibrium is 30 cm3.

Give the expression for the equilibrium constant, Kc, for this equilibrium and calculate its

value. Explain why it has no units.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (5)

(Total 12 marks)

131. Methane reacts with steam in an endothermic reaction.

CH4(g) + H2O(g) CO(g) + 3H2(g)

(a) State the effect on the value of the equilibrium constant of an increase in temperature.

.....................................................................................................................................

..................................................................................................................................... (1)

(b) Use your answer to (a) to explain the effect of this change on the position of equilibrium.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 3 marks)

132. This question is about the reaction of magnesium with hydrochloric acid which takes place

rapidly at room temperature.

Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) H = –467 kJ mol–1

(a) Rewrite the equation omitting spectator ions. (1)

(b) Suggest the sign of the following entropy changes for this reaction. Justify each of your

answers.

(i) Ssystem

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) Ssurroundings

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(iii) Stotal

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(c) A student carried out this experiment at five different temperatures in order to calculate

the activation energy of the reaction. The student‘s laboratory record is shown below.

Method Clean a strip of magnesium weighing 0.100 g with sand paper. Measure the temperature of

20 cm3 of 1.00 mol dm

–3 hydrochloric acid in a 100 cm

3 beaker. Add the magnesium ribbon,

stir continuously, and time how long it takes for the magnesium to disappear. Repeat the experiment at four other temperatures.

Assumption: the initial rate of reaction is proportional to 1/time.

Results

Temperature /°C

Temperature /K

1/T

/K–1

time /s

1/time

/s–1

ln 1/time

24 297 3.37 × 10–3

45 0.0222 –3.81

33 306 3.27 × 10–3

25 0.0400 –3.22

45 318 3.14 × 10–3

11 0.0909 -2.40

56 329 3.04 × 10–3

6 0.1667 -1.79

10 283 3.53 × 10–3

122 0.0082 -4.80

The Arrhenius equation is ln k = –Ea/R × (1/T) + constant

ln 1/time is proportional to ln k and so a graph of ln 1/time will have the same gradient as

that of the Arrhenius plot of ln k against 1/Temperature

The student plotted the graph of ln 1/time against 1/Temperature and from this the

activation energy, EA, was calculated as + 51.3 kJ mol–1

.

(i) Suggest the reason for cleaning the magnesium ribbon with sand paper.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(ii) Calculate the number of moles of hydrochloric acid used up when all the

magnesium reacts in one experiment. Hence comment on whether the change in

concentration during the reaction will have a significant effect on the validity of the

assumption that the initial rate of reaction is proportional to 1/time. How would

you overcome this potential error?

[Take the relative atomic mass of magnesium as 24 in this and subsequent

calculations.]

...........................................................................................................................

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...........................................................................................................................

........................................................................................................................... (5)

(iii) Use the value of H and other information given in the question to calculate the

temperature change in an experiment assuming no energy is lost to the

surroundings. Hence comment on whether this change in temperature will have a

significant effect. How would you overcome this potential error?

[H = –467 kJ mol–1

.

heat produced = mass × specific heat capacity × change in temperature.

Assume that the specific heat capacity of the solution is 4.18 J K–1

g–1

]

...........................................................................................................................

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...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (4)

(iv) The most difficult thing to measure accurately is the time it takes for the

magnesium to disappear and the time measured can be up to 2 seconds out.

Assuming this error, calculate the shortest time at 56 °C and the longest time at

10 °C for this reaction.

Complete the table for these times. Plot the two points on the grid below and join

them with a straight line. From the gradient, which equals –EA/R, of this line

calculate another value for the activation energy.

Temperature

/ °C

Temperature

/K

1/T

/K–1

time

/s

1/time

/s–1

ln 1/time

56 329 3.04 × 10–3

10 283 3.53 × 10–3

1/T(K–1)

0.0030 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036

–1.0

–1.5

–2.0

–2.5

–3.0

–3.5

–4.0

–4.5

–5.0

ln1

/t

(v) If the reaction mixture is not stirred, the magnesium tends to float on the surface of

the acid.

Suggest how this would affect the measurements of the rate of the reaction.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(vi) Suggest two other improvements the student could do to this experiment to

improve the accuracy or validity of the results.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(vii) If ethanoic acid of the same concentration and at the same temperature is used

instead of hydrochloric acid, explain how the rate would differ.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(Total 24 marks)

133. One step in the production of nitric acid is the oxidation of ammonia.

4NH3 + 5O2 4NO + 6H2O

This is carried out at 900 °C over a platinum-rhodium catalyst and is an example of

heterogeneous catalysis.

Explain in terms of collision frequency and collision energy how the rate would change if the

temperature were increased, and which of these causes the greater effect.

What is the difference between a heterogeneous and a homogeneous catalyst? Suggest one

advantage of using a heterogeneous catalyst in processes such as this.

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134. In moths a pheromone, P, acts as an attractant for the opposite sex. P has the molecular formula

C7H12O.

What can be deduced about the structure of P from the following information?

(a) (i) 1 mole of P reacts with 1 mole of Br2 molecules to form a compound with the

formula C7H12OBr2.

...........................................................................................................................

........................................................................................................................... (1)

(ii) When lithium tetrahydridoaluminate is reacted with P a compound with the

formula C7H14O is formed.

...........................................................................................................................

........................................................................................................................... (1)

(iii) P forms an orange precipitate with 2,4-dinitrophenylhydrazine.

........................................................................................................................... (1)

(iv) When P is heated with Fehling‘s or Benedict‘s solution, the solution remains blue.

...........................................................................................................................

........................................................................................................................... (1)

(v) P is a Z-isomer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(b) What does the following physical data tell you about the structure of P? Use your Data

booklet where necessary.

(i) The infrared spectrum of P has the following absorptions at wavenumbers above

1600 cm–1

.

3060 cm–1

2920 cm–1

1690 cm–1

1660 cm–1

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(ii) The nmr spectrum does not have a peak corresponding to a chemical shift, , of

between 9 and 10.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (1)

(iii) The mass spectrum showed the presence of peaks at mass/charge ratios of 15 and

29, but no peak at 43.

...........................................................................................................................

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...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (3)

(c) Given that P has a straight chain of carbon atoms in its formula, use the information you

have deduced above to suggest a displayed formula for the pheromone P.

(2)

(d) How could you use a purified sample of the orange precipitate in (a)(iii) to confirm the

formula of P?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (2)

(Total 16 marks)