Page of14

CHEMISTRY DEPARTMENTUNIVERSITY OF BOTSWANA

CHE 102 GENERAL CHEMISTRY II FINAL EXAMINATIONAPRIL 2004. TIME ALLOWED: 3 hours

Name of the student:

ill #:- '0 Group and Serial Number: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

WRITE ALL ANSWERS ON THIS QUESTION PAPER.

The paper has two parts. For Section A (multiple-choice questions), circle the letter for thecorrect answer for each question.For questions in Section B, use the space provided to write your answers. If you needadditional space, write on the back of the printed pages.

You may detach the Periodic Table, but you may NOT write anything on it during the."

IMPORT ANT: It is the student's responsibility to report if any page ismissing in this paper. The paper has 14 pages in addition to the PeriodicTable.

Specific heat capacity of H2O (1) = 4.184 J/(OC.g)

Kw= 1.0 x 10-14 at 25 °C

mort

Avogadro constant = 6.022 x 1023 mol-l

R = 8.314 J. K-1. mol-l = 0.08206 L. atm. K-1

1 atm = 760 Torr.

Unless otherwise stated, all solutions are aqueous and all temperatures are 25 DC.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Do not write in this table.

MC 2 3 4 5 Total1

exammatlOD.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Page 2 of 14

Section A: Multiple Choice Questions (60%)

Which of the following is the structure of 3,3-dimethyl-l-pentene1.

r-~=

>---~/ '"a) b) c)

x >=~e)

d)

Select the sequence of reagents from the given list which will best accomplishthe following transformation:

2.

CH3GH-CH2CH3CH3 C~C CH3IOH

a. H2SO4/H20/ HgSO4

H2/ Lindlar, then H2S0JH20b.

H2/Ni, then H2S04/ H2O

d. H202 /OH'

H2/Pt, then H20/ H2SO4e.

The addition of two moles of hydrogen bromide to I-pentyne will yield-3.

l,l-dibromopentane1,2-dibromopentane1,3-dibromopentane2,2-dibromopentane3,3-dibromopentane

a.b.c.d.e.

Page 3 of 14

4. How many mono chlorination products will be produced from the followingreaction-

C12H3C CH3

Light

86342

a.b.c.d.e.

5. The addition of water to cyclooctyne catalysed by sulphuric acid and mercury(II) sulphate will afford-

OH

OHOH

b) c) d) e)a)

6. Which of the following is the structure of3,5-dibromophenol?9H OH

OHBr BrBr Br

Br Br BrBr

Br

e)d)c)b)a)

7. The following compounds are-a

0II

CH3CH2CHandCH3 C CH3

a.b.c.d.e.

functional isomersskeletal isomersthe same moleculepositional isomersgeometric isomers

Page 4 of 14

8. The functional groups contained in the following structure are-

a. ketones, alcohol and carboxylic acidb. ketones, alcohol and acid anhydridec. ketones, cyclopropyl, alcohol and aldehyded. ketones, cyclopropyl, alcohol and ethere. ketones, alcohol, and ester

Calculate MIo (in kJ) for reaction 3 below:(1) 2NO -+ N2 + 02 MIo = -180 kJ(2) 2NO + 02 -+ 2N02 MIo = -112 kJ

(3) N2 + 202 -+ 2N02 MIo =?

9.

a. 68b. -68c. -292d. 292e. -146

10. Given the following /illofvalues:Substance ADof (kJ/mol)NOz(g) 34.0HzO(I) -286HNO3 (aq) -207NO(g) 90.0

Calculate the value of AHo (in kJ) for the reaction:3 NO2Cg) + H20(1) ~ 2 HNO3 (aq) + NO(g)

a. 64b. 140c. -140d. -508e. -64

Page 5 of 14

1. An unsaturated solution is one thata. has no double bond.b. contains maximum concentration of solute possible, and is in equilibrium with

undissolved solute.c. has a concentration lower than the molar solubility.d. contains more dissolved solute than the solubility allows.e. contains no solute.

12. The vapour pressure of pure water at 25 °C is 23.8 torr. Raoult's law predicts that asolution prepared by dissolving 18 g of glucose (MM = 180 g/mol) in 95 g of water will

have a vapour pressure of torr.

a. 24.3b. 23.8c. 0.451d. 0.443e. 23.4

a. lower, lower, lowerb. lower, higher, lowerc. lower, higher, higherd. higher, higher, lowere. higher, lower, higher

4. For the reaction below:N204(g) ~ 2NO2 (g)

determine the value ofKc if an initial concentration ofN2O4 (g) of 0.0400 mol/L isreduced to 0.0055 mol/L at equilibrium. There is no NO2 present at the start of thereaction.

a.b.c.d.e.

0.87130.220.0222.2 x 10-4

Page 6 of 14

15. The value ofKc for the equilibrium

Hz (g) + Iz (g) ~ 2HI (g)is 54.0 at 427 °C. At this temperature, what is the value ofKc for

HI (g) ~ Yz Hz (g) + Yz Iz (g)?

a. 27b. 7.35c. 0.136d. 2.92 x 103e. 3.43 x 10-4

16. The value ofKc for the reaction below is 0.016. Under a set of equilibrium conditions,[HI] = 0.10 M and [H2] = [h]. Calculate the concentration ofh (mol/L):2HI (g) ~ H2 (g) + h (g)

d. 1.3

0.31e.

7. The endothermic reactionPropene (g) ~ Cyclopropane (g)is at equilibrium. Which action(s) below will shift the equilibrium to the left and causethe amount of propene(g) to increase?

a. increasing the system temperatureb. decreasing the system temperaturec. increasing the system pressured. decreasing the system pressuree. increasing both the system temperature and the system pressure.

18. The [OH-] and pH of a 0.035 M NaOH solution at 25 °C are Mand

respectively.

a. 0.035, 1.46b. 0.035, -1.46c. 2.9 x 10.13, -12.54d. 0.035, 12.54e. 2.9 x 10'13, 12.54

Page 7 of 14

19. Of the acids in the table below, is the strongest acid

1.~1.~3.(6.~

HC2H302HCHO2HCIOHF

a.b.c.d.e.

HCzH)OzHCHOzHCIOHFHCzH)Oz and HCHOz

20 The Ka ofHCIO is 3.0 x 10-8 at 25°C. What is the pH at 25 °C of an aqueous solutionthat is 0.020 M HCIO?a. 2.45b. -2.45c. -9.22d. 9.22e. 4.61

21. An aqueous solution of will have pH greater than 7.0 at 25 °C.

a. ~NO3b. KBrc. NaId. CH3COONae. FeCI3

22. In which of the following aqueous solutions would you expect AgCI to have the highest...". ~

23. Which of the following pairs of substances can be dissolved to fonn a buffer solution?a. NaI, HIb. KCI, HBrc. ~CI, NH4NO3d. NaF, HFe. None of these

Ix]

Ix]

)x]

Ix]

0-50-40-80-4

SOlUDlllty"{a. pure waterb. 0.020 M BaC12c. 0.020 M NaCld. 0.020 M AgNO3e. 0.020 M KCl

Page 8 of 14

24. A reaction is found to be second order in carbon monoxide. If the concentration ofCa isdoubled, the rate of the reaction will .

a. doubleb. remain unchangedc. tripled. increase by a factor of 4e. decrease by a factor of 2.

25. The rate constant ofa first order reaction is 0.0271 S.l, The half-life of the reaction is

a.

b.c.d.e.

0.451 s40.9 s25.6 s0.625 sinitial concentration is required in order to determine the half-life.

26.

The initial concentration of a reactant in a first-order reaction is 0.27 M. The rateconstant for the reaction is 0.75 S.I. What is the concentration (mol/L) of reactant after

1.5 s?

a.3.8b.1.7c. 8.8 x 10-2d. 2.0 X 10-2e.0.135

27. In general, as temperature goes up, the rate of a reaction

a. goes up if the reaction is exothermic.b. goes up if the reaction is endothermic.c. goes up regardless of whether the reaction is exothermic or endothermic.d. stays the same regardless of whether the reaction is exothermic or endothermic.e. stays the same if the reaction is first order.

28. A catalyst increases reaction rate

a. by decreasing the heat of the reaction.b. by increasing the equilibrium constant.c. by changing the order of the reaction.d. by providing a reaction path with a lower activation energy.e. none of these could increase the reaction rate.

Page 9 of 14

29. When the temperature ofa reaction is increased from 303 K to 333K, the rate constantincreases by a factor of 10. (k2/k1 = 10). What is the activation energy (kllmol) of the

reaction?

a.b.c.d.e.

30. Which of the following graphs shows the correct relationship between concentration andtime for a reaction that is second order in [A]?

a.

time

b.[A]

time

c.l/[A]

time

d.

time

e,

time

3033466489

Page 10 of 14

Section B: 40%Question one (10 marks)(a) Hydrogenation ofC4H6, catalysed by Pt consumed two moles ofH2 to give C4H1O.

PtC4H6+ 2H2 ~ C4HIO

Draw all the isomers of C4~ in this reaction, and give their systematic names.

(b) Write the equation of the reaction in which I-pentyne is hydrated in presence of suI ph uricacid and HgSO4. Write the structure and the name of the major product.

c) The compound 2-methyl-2-butene reacted with water in presence of sulphuric acid to give analcohol. Write the reaction, give the structure and the name of the alcohol produced. What class(primary, secondary, tertiary etc) does the alcohol belong to?

of14Page

(9 marks)Question two

a. Find the order of the reaction with respect to CIO2.

b. What is the order of the reaction with respect to OH-c. What is the overall order?d. What is the value of the rate constant? Include the units of the rate constant with your

answer.

Page 12 of 14

..

Question Three. (7 marks)a. Assume that the molar solubility ofCaF2 in water is s. Express Ksp OfCaF2 in terms ofs.

b.

Given for PbS, Ksp = 8.0 X 10-28. Calculate the molar solubility ofPbS in water.

What is the molar solubility ofPbS in a 0.0180 M solution ofNa2S?(for PbS, Ksp = 8.0 x 10-28).

c.

Page 13 of 14

(8 marks)Question Four

Consider a 0.10 M solution of potassium benzoate, KC6HsCO2 (aq)Write the equilibrium that exists in the solution, and write the expression for the equilibrium

constant.Set up an equilibrium table.Ka of benzoic acid, C6HsCOOH = 6.5 x 10-s, calculate Kb for benzoate ion, C6HsCO2-

Calculate the pH of the given solution.

~~~

Page 14 of 14

Question Five (6 marks)

Consider the equilibrium:2802 (g) + Oig) ~ 2803 (g) LlliO = -198 kJ

a. what happens to the partial pressure of S03 when the partial pressure of S02 isdecreased?

b. What happens to the partial pressure of SO2 if the partial pressure of O2 is increased?

c If the volume of the container is increased, what happens to the amount of SO3?

d. lithe temperature of the system is increased, what happens to Kc?

If a catalyst is added to the system, what happens to Kp?eo

f. If the partial pressure ofSO3 is increased, what happens to Kp?

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