Chemistry paper 1, 2&3 KAHURO/MURANG’A EAST JOINT EXAMINATION - 2016 233/1 CHEMISTRY PAPER 1 (THEORY) JULY/AUGUST, 2016 TIME: 2 HOURS

1. A given sample of ink is a mixture of red dye, blue dye and orange dye. The blue dye is least absorbed than the rest and thered dye is most sticky.

(a) Complete the paper chromatogram below showing their separation. (1½mks)

(b) The above dyes are soluble in water. Describe how a pure sample of blue dye can be obtained. (1mk)(c) Name the solvent used in paper chromatography. (½mk)

2.

3.4.

5.

6.

Excess iron was allowed to rust in 2dm³ of most air and the volume of air remaining was measured at 1 atmospheric pressureeach day. The results were as follows.

Day 0 1 3 4 5 6 7 8Volume (cm³) 2000 1900 1720 1660 1620 1600 1600 1600

(i) Write an equation for the formation of rust. (1mk)(ii) On which day was the reaction complete. Explain. (1mk)(iii) What is the percentage volume of oxygen in air. Show your working. (1mk)State two properties of copper that make it suitable for making ornaments. (2mks)Give the IUPAC name of the following: (1mk)(i) CH3 CH2 COOCH2 CH3

(ii) Give the name of the homologous series to which the compound belongs. (1mk)(iii) Name and draw the alcohol that formed the compound in 4(i) above. (1mk)Consider the following equation.

On the same axis, sketch the graph when a catalyst is added and label all the essential parts. (2mks)A radioactive isotopes of lead undergoes radioactive decay in two stages are shown below.

216 i 212 i i 21285 Pb X Y

83 84

(a) Identify the particle emitted at each stage. (2mks)(b) State one use of radioactive isotopes. (1mk)

7. Aluminium chloride solution changes blue litmus paper red. Explain this observations. (2mks)8. Nitric (V) acid may be prepared in the laboratory by the action of concentrated sulphuric (VI) acid on a suitable nitrate and

distilling OFF the nitric (V) acid.(a) Why is the apparatus consisting of glass desirable? (1mk)(b) Pure nitric (V) acid is colourless but the products in the laboratory preparation is usually yellow. Explain.(2mks)

9. Describe how a solid sample of barium sulphate can be prepared starting with copper (II) oxide. (3mks)10. The results of an experiment to determine the solubility of potassium chlorate in water at 30°C were as follows.

Mass of dish = 15.86g. Mass of dish + saturated solution at 30°C = 26.8g. Mass of dish + solid potassium chlorate after evaporation to dryness = 16.86g. Calculate the mass of saturated solution containing 60g of water at 30°C. (3mks)

11. The melting point of phosphorous trichloride is -91°C while that of sodium chloride is 801°C. In terms of structure andbonding explain the difference in the melting point. (3mks)

Page | 165

Chemistry paper 1, 2&3 12. Study the reaction scheme below and answer the questions that follow.

A

CO2(g)

HeatStep I

C

NaOHB

HCl(g) CaCl2Pb(NO3)2 SolidStep II D

(i) Identify substances. A ,B , C, D (2mks)(ii) Write chemical equation for the reaction taking place in Step (II). (1mk)

13. (i) Explain why the ability of temporary hard water to conduct electricity falls when water is boiled, but it does not fall whentemporary hardness is removed by addition of washing soda. (2mks)

(ii) Name the ions that causes water hardness. (1mk)14. (i) State the Gay-Lussac’s Law. (1mk)

(ii) 15cm³ of a gaseous hydrocarbon reacted completely with 45cm³ of oxygen. 30cm³ of carbon (IV) oxide were formed.Determine the formula of the hydrocarbon given that all volumes of gases were measured under the same conditions oftemperature and pressure. (2mks)

15. (i) State the observation made when hydrogen sulphide gas is bubbled through aqueous lead (II) nitrate solution.(1mk)

(ii) Write an ionic equation for the reaction above. (1mk)16. Study the crude oil fractionating column in the diagram below. U

V W X Y

Crude oil Heat

Fractionating column

(i) How would you expect the temperature to vary from U to Y? (½mk)(ii) For each fraction given below, state at what position U, V, W, Z and Y it will be collected. (2½mks)

Compound with Position collectedC15 C25 atoms ………………………………………………………….C4 C15 atoms C20 Upwards C8 C16 atoms C1 C4 atoms

17. The apparatus below was set up for the preparation of oxygen gas in the laboratory.

(a) Name liquid Q. (1mk)(b) Write a balanced chemicals equation for the reaction that takes place in the reaction flask. (1mk)(c) Give a reason why it is preferred to use warm water to cold water when collecting oxygen gas. (1mk)18. 25cm³ of a solution of ammonium iron (II) sulphate (NH4)2 SO4. FeSO4 nH2O with concentration of 19.6g/l was titrated with

12.5cm³ of 0.02M acidified potassium manganate (VII). Given the equation.2 2 3

5Fe aq

MnO4

aq 8 H aq Mn aq 5 Fe aq 4 H 2 O l

Determine the value of n in the salt. (3mks)Page | 166

Chemistry paper 1, 2&3 19. Sulphur (IV) oxide and nitrogen (IV) oxide reacts as shown in the equation below.

SO2 + NO2 SO3(g) + NO(g)

(a) Using oxidation numbers show that this is a redox reaction. (2mks)(b) Identify the reducing agent. (1mk)

20. Zinc can be extracted through reduction then purified by electrolytic process.(i) Name two ores from which zinc can be extracted. (1mk)(ii) Name a substance that can be used as reducing agent in the furnace during extraction of zinc by reduction.

(1mk)21. A student was provided with 1.5g of XCO3. He reacted it with 50cm³ of 1M HCl which was excess. Determine the

volume of CO2 produced at S.T.P.(R.F.M of x CO3 = 100) molar gas volume at S.T.P = 22400cm³. (2mks)

22. Explain how a catalyst affects the following in a chemical reaction.(i) The enthalpy change. (1mk)(ii) The activation energy. (1mk)(iii) Chemical equilibrium. (1mk)

23. The scheme below represents the manufacture of a cleansing agent G.

R R SO3H + NaOH Cleansing agent G(i) Draw the structure of G and state the type of cleansing agent in which G belongs. (2mks)(ii) State one advantage of using G is as cleansing agent. (1mk)

24. The equation below represent equilibrium reaction between chromate ions and dichromate ions.

22CrO 4

(Yellow) 2 H Cr 2 O

(Orange)7 aq H 2O

(a) What is meant by the term dynamic equilibrium? (1mk)(b) State and explain the observation made if dilute sulphuric (VI) acid is added to

the equilibrium mixture. (2mks)25. Below is a set up of apparatus used to react ammonia gas with iron (II) chloride?

(a) State observation made in the beaker. (1mk)(b) Give a reason for using a funnel to deliver the ammonia into the beaker. (2mks)

26. Your lab technician noted that the reagent bottles of sodium carbonate, sodium chloride and sugar have lost their labels.Your chemistry teacher requested you to prepare and test aqueous solutions of each sample as shown below.

Bottle PH Electrical conductivity1 7 Conducts2 7 Does not conduct3 10 Conducts

Complete the table by filling the correct label for each bottle. (3mks)27. The diagram below represent large scale manufacture of hydrochloric acid.

Study it and answer the questions that follow.

Page | 167

Chemistry paper 1, 2&3 (a) Identify. (1mk)

(i) Gas A ………………….………………………………………………...(ii) Gas B ………………………………………………………………………

(b) Write the chemical equation for the reaction between gas A and B. (1mk)(c) State the role of glass beads in the process. (1mk)

28. (a) Using electrons in the outermost energy level, draw () and cross (x) diagram for H3O+ and C2H4 (H = 1, C = 6,O = 16)(i) C2H4 (1mk)(ii) H3O+ (1mk)

(b) What would be the effect of dipping litmus paper in aqueous solution of H3O+?(1mk)

Page | 168

Chemistry paper 1, 2&3 KAHURO/MURANG’A EAST JOINT EXAMINATION - 2016 233/2 CHEMISTRY PAPER 2 (THEORY) JULY/AUGUST, 2016 TIME: 2 HOURS

1. The grid below shows part of the periodic table. Use it to answer questions that follow. The letters do not represent theactual symbols of the elements.

S U VP R T WQ

(a) (i) Which of the element has the lowest ionization energy?

(ii) Explain your answer in a(i) above.(b) (i) Identify the most reactive non-metal.

(ii) Explain your answer in b(i) above.(c) Give the electronic configuration of element.

(i) S ………………………………………………………………..(ii) Q ………………………………………………………………..

(d) Compare the atomic radius of P and R. Explain.(e) The mass number of W is 40. Write down the composition of its nucleus.(f) Write formula of oxides of P.(g) (i) What is the name given to elements found in the shaded region.

(ii) Which elements can be used to provide an inert environment?2. (a) In which homologous series do the following compounds belong.

(i) CH3 CCH.(ii) CH3 CH2 COOH ……………………………………………...

(b) Raw rubber is heated with sulphur in the manufacture of natural rubber.(i) What name is given to the process?(ii) Why is the process necessary?

(c) Study the scheme given below and answer the questions that follow.

Potassium metalPropan-l-ol

IPolymer Bromine gas

(1mk)

(1mk)(1mk)(1mk)

(½mk)(½mk)(2mks)(1mk)(1mk)(1mk)(1mk)

(1mk)(1mk)

(1mk)(1mk)

Two products

Propene AC

II

Propane

Cracking

Hydrocarbon B Methane

(i) Write an equation for the reaction between propan-l-ol and potassium metal. (1mk)(ii) Name process I and II.(iii) Identify the products A and B.(iv) Name one catalyst used in Process II. (1mk)(v) Draw the structural formula of the repeating unit in the polymer C. (1mk)

(d) State two industrial uses of methane. (1mk)(e) Write the structural formula of 2, 3-dichloropropene. (1mk)

Page | 169

Chemistry paper 1, 2&3 3. Aqueous copper (II) sulphate was electrolysed using the set up represented by the diagram below.

(a) Apart from copper (II) ions and sulphate ions identify the ions in copper (II) sulphate solutions. (1mk)(b) Write an equation for the reaction at the:

(i) Anode ………………………………………………………….. (1mk(ii) Cathode ……………………………………………………….. (1mk)

(c) Using an arrow () indicate the direction of flow of electrons on the diagram. (1mk)(d) If in the above set up copper electrodes were replaced with inert electrodes. Write an equation for the reaction

which would occur at the anode. (1mk)(e) An iron spoon was to be electroplates with silver. Draw a well labelled diagram of the set-up of apparatus that

could be used to carry out the process. (3mks)(f) The table below shows ammeter readings obtained where different electrolytes of the same concentration were

tested.Electrolyte Ammeter readingCopper (II) sulphate solution 4.4Ethanoic acid 1.2

Explain why ethanoic acid gave a lower ammeter reading the copper (II) sulphate solution. (2mks)4. I The flow chart below is for the manufacture of sodium carbonate using Solvay process. Use it to answer the

questions that follow. Brine

Ammonioacal

Brine

Gas

M

(a) Name:

TowerP

Gas Q

Heatinglimestone

Add water

Chamber K

L

Filter

Chamber GSolution F Solid X

Heat

Na2CO3

(i) Gas M…………………………………………………… (1mk)(ii) Solution F ……………………………………..…….…. (1mk)(iii) Solid X ……………………………………………….… (1mk)(iv) The product L…………………………………………… (1mk)

(b) Write an equation for the reaction in chamber K. (1mk)(c) Name two raw materials used in Solvay process. (2mks)(d) (i) Name one substance recycled in Solvay process.

(ii) Give two reasons why carbon (IV) oxide is used as fire extinguisher. (2mks)(iii) Explain why lead carbonate is not reacted with dil. H2SO4 in preparation of carbon (IV) oxide in the

laboratory. (2mks)

Page | 170

Chemistry paper 1, 2&3 5. In order to determine the molar heat of neutralization of 1M potassium hydroxide, 200cm³ of 1M hydrochloric acid both

at the same temperature were mixed and stirred continuously with a thermometer. The temperature of the resultingsolution was recorded after every 30 seconds until the highest temperature of the solution was attained.(a) (i) Why was it necessary to stir the mixture of the two solutions? (1mk)

(ii) Define the term molar heat of neutralisation. (1mk)(iii) Write an ionic equation for the reaction. (1mk)

(b) The initial temperature for both solution was 24.5°C and the highest temperature attained by the mixture was30.9°C. Calculate the(i) heat change for the reaction.

(Specific heat capacity of the solution is 4.2Jg¯¹K¯¹, Density of the solution is 1.0gcm¯³).The volume of KOH used was 200cm³. (2mks)

(ii) molar heat of the neutralisation. (2mks)(c) If ammonium hydroxide was used instead of potassium hydroxide the heat of neutralization would be different

from the one obtained in b(ii) above.Explain the difference. (3mks)

(d) Draw an energy level diagram for the reaction between potassium hydroxide and hydrochloric acid.(3mks)

6. I The extraction of iron from its ores takes place in the blast furnace. Below is a simplified diagram of a blastfurnace. Study it and answer the questions that follow.

(a) Name(i) One substance in the slag.(ii) Another iron ore material used in the blast furnace.

(b) Describe the processes which lead to the formation of iron in the blast furnace. (3mks)(c) What is the use of limestone in the blast furnace? (1mk)(d) Give a reason why the melting point of the iron obtained from blast furnace is 1200°C while that of

pure iron is 1535°C. (1mk)(e) State two uses of steel. (1mk)

II (a) Write the formula of compound formed when iron reacts with dil hydrochloric acid.(b) Name a compound of iron which sublimes on heating. (½mk)

7. The table below gives the volumes of the gas produced when different volumes of2M hydrochloric acid were reacted with 0.6g of magnesium powder at room temperature.

Volume of 2M HCl (cm³) Volume of the gas (cm³)0 010 24020 48030 60040 60050 600

(a) Write an equation for the reaction between magnesium and hydrochloric acid. (½mk)(b) On the grid provided plot a graph of the volume of the gas produced (vertical axis) against volume of acid

added. (Note that before the reaction comes to completion, the volume of gas produced is directly proportionalto the acid added. (3mks)

(c) From the graph, determine(i) the volume of gas produced if 12.5cm³ of 2M HCl had been used. (½mk)(ii) The volume of 2M HCl acid which reacted completely with 0.6g of magnesium powder. (1mk)(d) State and explain the effect on the rate of production of the gas if(i) 0.6g of magnesium ribbon was used. (2mks)(ii) 2M hydrochloric acid at 15°C was used instead of room temperature.(e) Given that one mole of the gas occupies 24000cm³ at room temperature.

Calculate the relative atomic mass of magnesium. (3mks)

Page | 171

Chemistry paper 1, 2&3 233/3 CHEMISTRY PAPER 3 (PRACTICAL) CONFIDENTIAL KAHURO/MURANG’A EAST JOINT EXAMINATION - 2016

In addition to the common apparatus and fittings found in a Chemistry laboratory, each candidate should be provided with; - Solid A (Six pieces of 1cm long magnesium ribbon)- 1 boiling tube.- Distilled water in a wash bottle.- 1 filter funnel.- 1 filter paper.- 1 label.- Solid B (1g).- Solid W (1g).- Universal indicator paper and a pH chart.- About 60cm³ of solution Y 0.4M sodium carbonate solution.- About 120cm³ of solution X 2M hydrochloric acid.- A pipette (25ml).- A burette.- 10ml measuring cylinder.- A stop watch.- 100ml beaker.- Stirring rod.- Sodium hydrogen carbonate (About 1g).

ACCESS TO:- 2M NaOH solution.- Ammonia solution (2M).- Bunsen burner.- Lead (II) nitrate solution.- Acidified potassium manganate (VII) solution.- Methyl orange indicator.- Dilute nitric (V) acid.- Sodium chloride solution.

NB:- Solid B is a mixture of sodium sulphate and lead (II) carbonate in a ratio of 1: 1.

Prepare solid B for each candidate separately.- Solid W is maleic acid.

Page | 172

Chemistry paper 1, 2&3 KAHURO/MURANG’A EAST JOINT EXAMINATION - 2016

233/3 CHEMISTRY PAPER 3 (PRACTICAL) JULY/AUGUST, 2016 TIME: 2¼ HOURS

1.----

(i)(ii)

You are provided with:2M hydrochloric acid solution X.Magnesium ribbon.0.4M sodium carbonate solution Y.Solid A (six pieces of 1cm long magnesium ribbon).You are required to determine:-The rate of reaction between hydrochloric acid and magnesium.The mass of 1cm of magnesium ribbon.

PROCEDURE IUsing a measuring cylinder, measure 20cm³ take 1 piece of 2M hydrochloric acid, solution X and place it in a clean 100ml beaker. Cut a 1cm piece of magnesium ribbon and place it in the 100ml beaker containing 2M hydrochloric acid and immediately start the stop clock/watch; measure and record the time taken for the magnesium ribbon to react completely with 2M hydrochloric acid in the table below. Retain the resultant solution by transferring it into a 100ml measuring cylinder then adding distilled water to make 100ml of solution, label this solution Z. Reserve solution Z for use in procedure II. Measure 18cm³ of hydrochloric acid accurately, add 2cm³ of distilled water to make the total volume 20cm³. Transfer the contents into the 100ml beaker,place another piece of 1cm length magnesium ribbon in the beaker then swirl and record the time taken for it to completely react. Repeat this procedure by measuring the volumes of the acid and distilled water as in table I below.Retain the remaining solution X for question 2.

TABLE IVolume of 2M Volume of water Time taken for 1

Experiment hydrochloric acid (cm³) magnesium ribbon to

12345

(a) Plot a graph of 1T im e

(cm³)

2018161412

against volume of the acid.

react completely (sec)

02468

Time(sec¯¹)

(6mks)(3mks)

(b) From the graph determine the time taken for the ribbon to react completely with 17cm³ of 2M hydrochloric acid. (2mks) PROCEDURE II Fill the burette with solution Y. Pipette 25cm³ of solution Z into a conical flask. Add 2 drops of methyl orange indicator. Titrate solution Z with solution Y to complete the titration table II below.

(4mks) TABLE II

I II IIIFinal burette reading Initial burette reading Volume of solution Y used.

Calculate: (i) Average volume of solution Y. (1mk)(ii) Number of moles of solution Y used. (1mk)(iii) Number of moles of hydrochloric acid in 25cm³ of solution Z. (1mk)(iv) Number of moles of hydrochloric acid present in 100cm³ of solution Z. (1mk)(v) Number of moles hydrochloric acid present in 20cm³ solution X. (1mk)(vi) Number of moles of hydrochloric acid that reacted with 1cm of magnesium ribbon. (1mk)(vii) Mass of magnesium present in 1cm length of magnesium ribbon. (Mg = 24). (1mk)

2. You are provided with solid B. Use it to carry out the tests below. Write your observations and inferences in the spacesprovided. Place all solid B in a boiling tube, add about 10cm³ of distilled water and shake thoroughly. Filter the mixtureobtained. Retain the residue for tests (b) below. Divide the filtrate into 2 portions.

Page | 173

Chemistry paper 1, 2&3 (a) (i) To portion (i), insert a clean stirring rod and place it on a non-luminous

flame of a Bunsen burner.Observation Inference

(1mk) (1mk)

ii) To portion (ii), add about 3 drops of lead (II) nitrate solution, then warm.Observation Inference

(1mk) (1mk)

(b) Dissolve the residue in about 8cm³ of dilute nitric (V) acid solution anddivide the resulting solution.

Observation Inference(1mk) (1mk)

(i) To portion (i), add sodium hydroxide solution, dropwise, then in excess.Observation Inference

(1mk) (1mk)

(ii) To portion (ii), add sodium chloride solution and then warm.Observation Inference

(1mk) (1mk)

3. You are provided with solid W. Place it in a boiling tube and about 10cm³ of distilled water and shake. Divide theresulting solution into 3 portions.

Observation Inference(1mk) (1mk)

(i) Use the first portion to determine the pH of the solution.Observation Inference

(1mk) (1mk)

(ii) To the second portion, add about half spatula of sodium hydrogen carbonate.Observation Inference

(1mk) (1mk)

(iii) To the third portion, add about 3 drops of acidified potassium manganate (VII).Observation Inference

(1mk) (1mk)

Page | 174

o e

Chemistry paper 1, 2&3 KAHURO/MURANG’A EAST JOINT EXAMINATION - 2016 233/1 CHEMISTRY PAPER 1 MARKING SCHEME

1. (a)

(b) - Wash the blue spot in the chromatogram with plenty of water.¹- Evaporate the water to obtain the dye. ½

(c) Ethanol/propanone. ½2. (a) (i) 4Fe(S) + 3O2(g) + nH2O(l) 2Fe2O3(S) ½

(ii) 6th day ½ - volume of air ½ remains constant.(iii) % of oxygen gas 2000 1600 ¹

3. - Good appearance/metallic lustre.- Does not rust.- Malleable.- Ductile.

4. (a) (i) Ethylpropanoate. ¹(ii) Ester/Alkylakanoate(iii) H H

H C C OH

H H

5.

6. (a) (i) Alpha ()

200020% ¹

½

100

Ethanol ½

(ii) Beta 1

(b) - Cancer treatment.

- Detecting cracks in metal.- Carbon dating of plants and animals.

7. Aluminium chloride hydrolyses ½ in water to form an acidic solution ½ presence of H+ ½ in the solution makes itacidic. ½OR AlCl3 + 6H2O [Al(H2O)6] + 3Cl¯

3 (Al(H2O)6)3+ AlOH 5 OH aq H aq

8. (a) Nitric (V) acid is a strong oxidizing agent and attacks rubber corks and rubber tubes. ¹(b) Contains dissolved nitrogen (IV) oxide which results from decomposition of nitric (V) acid. ¹

9. - Put excess CuO ½ in dilute H2SO4.- Filter excess CuO ½ - Add BaCl2/Ba(NO3)2 solution ½ - Filter to get BaSO4 ½ - Wash the precipitate with distilled water. ½ - Dry the precipitate between filter paper. ½

10. Mass of KClO3 = 16.86 - 15.86 = 1g ½Mass of water = 26.86 - 16.86 = 10g ½

Page | 175

Chemistry paper 1, 2&3 1g of KCO3 saturates 10g of water at 30°C. ½ g of KCO3 saturates 60g of water at 30°C.

6 1

1

= 6g ½

Mass of saturated solution = 6 + 60 = 66g ½11. PCl3 - have simple molecular structure ½ and weak van der waal forces. ½ NaCl - has ionic bond ½ and giant

ionic ½ structure ionic bonds are stronger than van-der-waal bond hence high melting point. ¹12. (i) A - CaCO3 ½

B - Na2CO3 ½C - CaO ½D - PbCl2 ½

(ii) Pb(NO3)2(aq) + CaCl2(aq) PbCl2(S) + Ca(NO3)2(aq) ¹13. (i) Boiling removes Ca2+/Mg2+ in water, this reduces conductivity of particles. ¹

Addition of washing soda, add Na+ ions in water therefore restoring the conductivity of particles. ¹(ii) Magnesium and calcium ions.

14. (a) When gases react they do so in volumes which bear simple whole number ratio to one another and to the volumeof products if gaseous temp and pressure remaining constant. ¹

(b) C Hy + O2(g) CO2(g) + H2O(g)

15 45 30 30

15. (a)

15 15 151 3 2

C H

y + 3O

2 2CO2(g) + 2H2O(g) ¹C

Hy C2

H4 ½

Black precipitate. ¹2 2

215 ½

(b) Pb S PbS ¹ aq aq S

16. (i) Increases/rises. ½(ii) U - C1 - C4

V - C4 - C15

W - C9 - C16

X - C15 - C25

Y - C20 upwards 17. (a) Water ¹

(b) 2Na2O2(S) + 2H2O(S) 4NaOH(aq) + O2(g) ¹(c) Oxygen is insoluble in warm water. ¹

0 02 12 518. Moles of MnO 4 used ½

1000 cm 3= 0.00025 moles

Moles of Fe2aq used 0.00025 moles x 5/1 ½

= 1.25 x 10¯³ molesMolarity of Fe2+ = 1.25 x 10¯³ moles - 25cm³

- 1000cm³1000 1 25 10 3

25 0 05 M ½

0.05 moles - 19.6g1 moles - ?

1 19 6 ½0 05

(NH4)2 SO4. FeSO4. nH2O = 392 ½ 284 + 18n = 392

18 n 108

392

18

19. (a)

18

n = 6 ½

SO2(g) + NO2(g) SO3(g) + NO(g)

N + (-2 x 2) = 0 S + (-2 x 3) = N + (-2) = 0S + (-2 x 4) = 4) N = 4 ½ S = +6 N = +2 ½S = +4O.N of S increased from +4 to +6 - Oxidation ½ O.N of N decreased from +4 to +2 - Reduction ½

Page | 176

Chemistry paper 1, 2&3 (b) SO2 ¹

20. (i) Zinc blende/calamite(ii) Carbon/carbon (II) oxide.

21. XCO3(S) + 2HCl(aq) XCl2(aq) + H2O(l) + CO2(g) ½1 2 1 1 1

100g - 22.4 litres 1.5g - ? 1 5 22 4

½ 100

= 0.336 ½ 22. I Does not change (No effect) ¹

II Lowered/reduced ¹III No effect but attained at a faster (quicker) rate ¹

23. (i)R SO3Na

Soapless detergent ¹

¹ (ii) - It does not form scum with hard water.

- No wastage of soap // time.- No staining of clones.

24. (a) Reaction that has attained a state of balance whereforward ¹ and backward reaction is taking place at the same rate.

(b) Orange colour intensifies ¹ equilibrium shift to the right andforward reaction is favoured. ¹

25. (a) Green precipitate formed.(b) - To prevent sucking back.

- To increase surface area for absorption- NH3 is highly soluble.

26. (i) Sodium chloride. ¹(ii) Sugar. ¹(iii) Sodium carbonate. ¹

27. (a) A - Chlorine. ½B - Hydrogen. ½

(b) H2(g) + Cl2 2HCl(g) ¹(c) To increase surface area for dissolution of hydrogen chloride gas

in water. ¹

28.

(b) Blue litmus paper changes to red. H 3 O aq H 2 O l H

H+ makes solution acidic

Page | 177

Chemistry paper 1, 2&3 KAHURO/MURANG’A EAST JOINT EXAMINATION - 2016 233/2 CHEMISTRY PAPER 2 MARKING SCHEME

1.

2.

3.

(a)

(b)

(c)

(d)

(e)

(f)(g)

(a)

(b)

(c)

(d)

(e)

(a)(b)

(i) Q ¹mk(ii) It has the longest atomic radius // has the highest number of energy levels¹mk(i) U ¹mk(ii) Has the shortest atomic radius // has the highest effective nuclear charge.(i) 2.6 ½ mk(ii) 2.8.8.1 ½ mkP is longer than R. ¹mkP has lower effective nuclear charge ¹mk22 - Neutrons ¹mk

18 - Protons ¹mkP2O ½ P2O2 ½Reject OP2 and O2P2

(i) Transition metals ¹mk(ii) V and W ¹mk(i) Alkynes(ii) Alkanoic/carboxylic acids(i) Vulcanisation ¹mk(ii) Toughen/harden/strengthen the rubber. ¹mk(i) 2CH3 CH2 CH2 OH(aq) + 2K(S) 2CH3 CH2 CH2OK(aq) + H2(g) ¹mk(ii) I Dehydration ¹mk

II Hydrogenation ¹mk(iii) A - 1, 2-dibromopropane ¹mk

B - Ethene ¹mk(iv) Nickel(v)

¹mkH H

C C

HH C H

H

- As fuel- To make carbon k ½mk

Cl H

H C C = C ¹mk

H Cl H

H+, ½mk OH- ½mk(i) Anode Cu(S) Cu2+ + 2e- ¹mk

2

¹mk

(ii) Cathode Cu aq 2e Cu S ¹mk(c) On the diagram ¹mk

Page | 178

Chemistry paper 1, 2&3

4.

5.

(d)

(f)

I

(a)

4OH(aq) 2H2O(l) + O2(g) + 4e- ¹mk

Ethanoic acid is a weak acid is a weak acid and dissociates partially giving fewer ions copper (II) sulphate dissociates fully and gives more ions in solution, hence a better electrolyte than ethanoic acid. (a) (i) Ammonia ¹mk

(ii) Ammonium chloride ¹mk(iii) Sodium hydrogen carbonate. ¹mk(iv) Calcium chloride/water ¹mk

(b) Ca(OH)2(aq) + 2NH4 Cl(aq) CaCl2(aq) + 2H2O(l) + 2NH3(g)

(c) CaCO3, CO2, NH3, Brine - Names only(d) (i) CO2, NH3, water - Accept names only

(ii) - Is denser than air. ¹mk- Doesn’t support combustion. ¹mk

(iii) There is formation of PbSO4, ½mk which is insoluble, ½mkThe PbSO4 coats PbCO3, ½mk this stops further reaction. ½mk

(i) To distribute heat uniformly // uniform mixture of reagents. ¹mk(ii) Heat evolved when one molar of water is formed from the reaction

between H+ and OH- ions. ¹mk

(iii) OH aq H aq H 2 Ol ¹mk(b) (i) T = 30.9 - 24.5 = 6.4 ¹mk

Heat = 400 x 4.2 x (30.9 - 24.5) ¹mk

¹mk10752J

(ii) Moles of KOH use 200 11000 0 2 ¹mk

0.2 moles 10752J

1 mole 10752 107520 ¹mk0 2 2

= 53.35= -53.36kJ ¹mk

(c) Lower, ¹mk ammonium hydroxide is weaker ¹mk base some energy used to ionize. ¹mk(d)

KOH(aq) + HCl(aq)

H = 53.36 ¹

KCl(aq) + H2O(l) ¹

6. I (a) (i) Calcium silicate.(ii) - Magnetite.

- Siderite.- Iron pyrite

Reaction path ½

(b) Carbon reacts with O2 to form carbon (IV) oxideC(S)

+ O2(g)

CO2(g)

¹mk Carbon (IV) oxide react with C to form carbon (II) oxide

CO2(S) + C(S) 2CO(g) ¹mk Iron (III) oxide react with carbon (II) oxide to form iron and carbon (IV) oxide. Fe2O3(S) + 3CO(g) 2Fe3(S) + 3CO2(g) ¹mk Accept equation // description using statements.

(c) Produce CaO ½mk which react with silica/SiO2 and aluminium oxide to form slag. ½mk(d) Cast iron // iron obtained is impure,½mk impurities lower melting point. ½mk(e) - Making railway lines ½mk

- Making iron nails. ½mk - Making engine blocks. - Make surgical instrument. - Making spoons.

Any correct

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Chemistry paper 1, 2&3

7.

II

(a)(b)(c)

(d)

(e)

(a) FeCl2 ½mk(b) Iron (III) chloride ½mk

Mg(S) + 2HCl(aq) MgCl2(aq) + H2(g)

On the graph(i) 320cm³ 4cm³ from the graph(ii) 25cm³ 0.5 from the graph(i) Will be reduced/less/lowered, ¹mk as surface area ¹mk

of ribbon is less than powder. WTTE(ii) Reduced/less/lowered, ¹mk K-energy of reactants will be less

they will be less collision WTTE ¹mkFrom equation in 7(c) aboveMoles of Mg = moles of H2 released ½mk

600 ¹mk = 0.025 24000

0.025 moles of Mg 0.6g of Mg1 mole of Mg 0 6 ¹ = 600

0 025 25= 24 ½mk

Penalize ½mk of units are included

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Chemistry paper 1, 2&3 KAHURO/MURANG’A EAST JOINT EXAMINATION - 2016 233/3 CHEMISTRY PAPER 3 MARKING SCHEME

Experiment Volume of 2M HClacid cm³

1 202 183 164 145 12

Volume of Time taken forwater (cm³) magnesium ribbon to

react completely (sec)

0 162 224 246 298 47

1timeSec¯¹

0.06250.04550.04170.03450.0213

(i) Complete table (3mks)4 and 5 readings (3mks)3 readings (2mks)Readings below readings…………………………………………………... (0mks)

(ii) Decimal ……………………………………………………………………… (1mk)Accept consistent 1 decimal place.Accept whole number used consistently.Reject two decimal places.

(iii) Accuracy mark……………………………………………………………… (1mk)First reading (Experiment 1) compare with the school value or teaches values.If within 2 ………………………………………………………………… (1mk)If outside 2 ……………………………………………………………….. (0mk)

(iv) Trend ………………………………………………………………………. (1mk)Time taken must register a continuous rise from experiment1-5.Award zero mark incase is a decreases in time taken.

(a)

(b) Award 1mk if correctly shown from a correctly drawn graph.(c) The rate of reaction is inversely proportional to time taken. (1mk)

Table III II III (i) Complete table ……. (1mk)

Final burette reading 12.8 25.6 38.0 (ii) Decimal…………... (1mk)Initial burette reading 0.0 12.8 25.6 (iii) Accuracy ………... (1mk)

(iv) Averaging ……..… (1mk)Titre 12.8 12.8 13.0 (v) Final answer …..…. (1mk)

(5mks)

(i) Complete table……………………………………………………….. (1mk)Conditions3 titration done and consistent…………………. 0.2 …………….. (1mk)2 titration done and consistent…………………. 0.2 …………….. (½mk)1 titration done and consistent ………………………………………. (0mks)

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Chemistry paper 1, 2&3 Penalties Penalize ½mk once for any of the following arithmetic error. Penalties table II complete table. - Unrealistic burette readings i.e. >50cm³ or <1cm³ titre value.- Inverted table.

(ii) Decimal mark (1mk)1 or 2d.p to be used consistently.If 2d.p are used the last digit must be ‘0’ or ‘5’NB: Penalize fully if decimal is missing or used inconsistently.

(iii) Accuracy ………………………………………………………….. (1mk)Pick any titre close to the teacher average value and compare, if thedifference is 0.1 …………………………………………………………………. (1mk)0.2 …………………………………………………………………. (½mk)Beyond 0.2 …………………………………………………………. (0mk)

(iv) Principles of averaging ………………………………………………. (1mk)Titre 1 Titre 2 Titre3

3½

Conditions

Corrections ½ (1mk)

- All consistent values must be averaged otherwise penalize fully … (1mk)- Reject average of inconsistent titre readings. - A working must be shown otherwise penalize (½mk) - Answer must be to 4d.p otherwise penalize (½mk) unless it works out to less d.p. - Accept answer if no units shown penalize (½mk) if wrong units shown.

(v) Final answer ……………………………………………………………. (1mk)Compare the candidates average time with the teachers average -if the difference is with 0.1 …………………………………………. (1mk) 0.2 …………………………………………………………………. (½mk)Beyond 0.2 …………………………………………………………. (0mk)

CALCULATIONII Number of moles 0.4 x Ans I above (½mk)

0 4 AnsI aboveOf solution Y (½mk)

1000III No of moles

Moles ratio Y: X = 1: 2 Moles HCl = 2 x Ans II above

= Correct answerIV Moles present in solution

Ans III above 1000

= (½mk) Correct answer I

Z V Moles of X

252 201000

Correct Ans 0 4 moles

VI Moles of original solution = 0.04 moles.Moles of HCl from solution Z = Correct Ans IV.Moles of HCl reacted with Mg = Correct Ans.

AnsinVIVII Mass of Mg 24 CorrectAns

2

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Chemistry paper 1, 2&3 GATUNDU SOUTH FORM FOUR EVALUATION EXAMINATION Kenya Certificate of Secondary Education 233/1 CHEMISTRY PAPER 1 THEORY JULY / AUGUST 2016 2 HOURS

1. (a) Distinguish between ionization energy and electron affinity. (2 marks)(b) The atomic number of Q and R are 9 and 17 respectively. Compare the electron affinity of Q and . Explain. (1 mark)

2. The relative atomic mass of an element is 10.28, it has two isotopes 10 R and 11 R.5 5

Calculate the relative percentage abundance of each isotope. (3 marks)3. The diagram below shows spots of pure substances A, B and C on a chromatography paper. Spot D is that of a mixture.

After development A, B and C were found to have moved 9cm, 4cm and 7cm respectively D has separated into two spots which moved 7cm and 9cm.

(a) On the diagram (i) Using 5 units in the alongside scale to represent 1cm Show the position of all the spots after development.

(2 marks) (ii) Identify the substances present in mixture D. (1 mark)

4. Describe how solid Aluminium chloride can be separated from a solid mixture of sodium chloride and ammonium chloride.(3 marks)

5. The number of protons and neutrons of atoms W, X, Y and Z are shown in the table below.Atom No. of protons No. of neutronsW 6 6X 12 12Y 6 8Z 17 20

(a) Write down the electronic configuration of X. (1 marks)(b) (i) Which one of the atoms is of an element in group (VII) of the periodic table.

(ii) Name the type of bond which is formed when X and Z reacts. (1 mark)6. The table below gives the solubility of potassium bromide and potassium sulphate at 00C and 800C.

Substance 00C 800

Potassium bromide 58 g/100g water 77 g/100g water

Potassium sulphate 18 g/100g water 20 g/100g water

When an aqueous mixture containing 60g of potassium bromide and 7g of potassium sulphate in 100g of water was cooledfrom 800C to 00C, some crystals were formed.(a) Identify the crystals. (1 mark(b) Determine the mass of crystals formed. (1 mark)(c) Name the method used to obtain the crystals. (1 mark)

7. What is the colour of the following. (2 marks)

Metal oxide Colour when hot Colour when coldZinc (II)oxideLead (II) oxide

8. The diagram below represents a set up that was used to show that part of air which is used during burning.

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Chemistry paper 1, 2&3 (a) If excess phosphorus was used in the set up. Draw a diagram of the set up at the end of the experiment when there was

no further observable change. (2 marks)(b) Suggest one modification that should be made on the apparatus if the percentage of the air used is to be determined.

(1 mark) 9. Use the scheme below to answer the questions that follow.

(a) Identify the substances H and J.(b) State one commercial use of solid J. (1 mark)

10. Sulphur exists in two crystalline forms(a) Name one crystalline form of sulphur. (1 mark)(b) Give any two uses of sulphur. (2 marks)

11. (a) The equation below represents a redox reaction.2FeCl2 (aq) + Cl2 (g) → 2FeCl3 (aq)

Identify the oxidizing agent. Give a reason. (2 marks)(b) What is the oxidation number of chlorine in ClO-4 ? (1 mark )

12. The column below was used to soften water

(a) Explain how the hard water was softened as it passed through the column. (1 mark)(b) After some time the material in the column is not able to soften hard water.

How can the material be reactivated? (1 mark)(c ) State one advantage of using hard water for domestic purposes. (1 mark)

13. In an experiment magnesium ribbon was reacted with dilute sulphuric (VI) acid and the volumeOf hydrogen gas produced with time noted. The graph below shows the volume of gas produced with time

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Chemistry paper 1, 2&3 Explain the following observations.

(i) The curve of the graph is steepest at the beginning. (1 mark)(ii) The curve of the graph completely flattens at region AB. (1 mark)(iii) On the same axis plot the curve that would be obtained if the acid used was ethanoic acid. Label it ethanoic acid

(1 mark)14. Ammonia gas was passed into water as shown below.

(a) What is the use of the inverted funnel. (1 mark)(b) Explain why the pH of the solution is above 7. (1 mark)(c) Explain why hydrochloric acid displays acidic properties when dissolved in water, while in methylbenzene, the acid does

not display the acidic properties. (1 mark)15. 60cm3 of oxygen gas diffused through a porous partition in 50 seconds. How long will it take 120cm3 of sulphur (IV) oxide

gas to diffuse through the same partition under the same conditions. (3 marks )16. The data below was recorded when metal K was completely burnt in air. K is not the actual symbol of the metal.

(R.A.M; K = 56, O = 16 )Mass of empty crucible and lid = 10.240gMass of crucible, lid and metal K = 10.352gMass of crucible, lid and metal oxide = 10.400g

(a) Determine the mass of(i) Metal K (½mark)(ii) Oxygen (½ mark)

(b) Determine the empirical formula of the metal oxide. (2 marks)17. Study the flow chart below and answer the question that follow.

(b)What name is given to the type of reaction in step 2 ? (1 mark )18. The set -up below was used to electroplate a metallic spoon. Study it and answer the questions that follow .

(a) Write an equation for the reaction that occurred at the anode. (1 mark)(b) State and explain what happened to the cathode. (2 marks )

19. The structures below represents two cleansing agents(A) R - COO - Na+

(B) R - OSO3 - Na+

(a) In the table below, give one advantage and one disadvantage of using each of them. (2 marks)Advantage Disadvantage

R - COO - Na+

R - OSO3 - Na+

(b) Which of the two cleaning agents is the better for washing. Explain. (1 mark)

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Chemistry paper 1, 2&3 20. The table below shows the observations made on tests carried out on a colourless liquid sample.

Exp Test Observation(i) Addition of excess NaOH (aq) White precipitate soluble in excess(ii) Addition of dilute H2SO4 (aq) White precipitate(iii) Addition of AgNO3 (aq) White precipitate

(a) Identify (i) Cation in the sample _______________________________________ (1 mark)(ii) Anion in the sample _____________________________________ (1 mark)

(b) Write the ionic equation for the reaction taking place in experiment (III). ( 1 mark )21. An experiment was set as shown below

(a) Name the gas F (1 mark )(b) State one physical characteristic of gas F. (1 mark )(c ) What would be observed if a litmus paper was put in a solution of gas F. (1 mark)

22. At 200C NO2 ; N2O4 gases exist in equilibrium as shown in the equation below.2NO2 (g) N2O4 (g) H = -ve(Brown ) (pale yellow )

(a) What is the significance of the negative sign as in the equation above. (1 mark)(b) State and explain the observations that would be made when

(i) a syringe containing the mixture was immersed in warm water. (1 mark)(ii) The volume of the gaseous mixture in the syringe was increased. (1 mark)

23. (a) Explain why its not advisable to use woodash for cleaning aluminium utensils. (1 mark)(b) Aluminium metal is a good conductor and its used for over-head cables. State any other two properties that makes

aluminium suitable for this use. (2 marks )24. Study the information in the table below and answer the questions that follow.

Bond Bond energyC - H 414Cl - Cl 244C - Cl 326H - Cl 431

Calculate the enthalpy change of the reaction: (3 marks)CH4 (g) + 2 Cl2 (g) U.V CH2 Cl2 (g) + 2 HCl (g)

Light 25. Urea (NH2)2CO is prepared by the reaction between ammonia and carbon (IV) oxide gas.

2NH3 (g) + CO2 (g) → (NH2)2 CO (aq) + H2O (l)

In one process, 620kg of ammonia were reacted with excess carbon (IV) oxide gas.Calculate the mass of the urea that was formed.(H = 1.0, C =12.0, N = 14,O = 16 and RMM of ammonia is 17 ) (3 marks )

26. Below is a list of oxides.MgO, N2O, K2O, CaO and Al2O3

From the above list select(a) A neutral oxide. (1 mark )

(b) An oxide that can react with both potassium hydroxide and dilute hydrochloric acid. (1 mark)(c ) What property is exhibited by the reaction in b above. (1 mark )

27. a) The electronic configuration of an ion P2- is 2.8.8.. Draw the structure of the atom just above element P in the periodictable. (2 marks )

28. State one use of a luminous flame. (1mark)

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Chemistry paper 1, 2&3 GATUNDU SUB-COUNTY EVALUATION EXAMINATION

233/2 CHEMISTRY Paper 2 (THEORY) July/Aug 2016 2HOURS

1. The grid below represents part of the periodic table. Study it and answer the questions that follow. The letters do not represent the actual symbols of the elements.

Q O R S

T UV Z

a) (i) Which element will require the least amount of energy to remove one of its outermost electrons, explain. (1mark)(ii) Select the most reactive non-metal (1mark)(iii) What name is given to the family of elements to which T belong? (1mark)(iv) Between S and R, which element has a smaller atomic radius, explain. (2marks)(v) Which of the elements have a tendency of forming covalent bonds? Explain. (1mk)(vi) Write the formula of the compound formed when U reacts with T, state the type of body formed.

Formula (1mark)Bond (2marks)

2. (a) A student set up the apparatus as shown in the diagram below to prepare and collect dry ammonia gas.

(i) Identify one mistake in the set-up and give a reason. (2marks)(ii) Name a suitable drying agent for ammonia. (1mark)(iii) Write an operation for the reaction that occurred when a mixture of ammonium chloride and calcium hydroxide was

heated. (1mark)(iv) Describe one chemical test for ammonia gas. (2 marks)

(b) The first step in the industrial manufacture of nitric (v) acid is the catalytic oxidation of ammonia gas.(i) What is the name of the catalyst used? (1mark)(ii) Write the equation for the catalytic oxidation of ammonia gas. (1mark)(iii) Nitric (v) acid is used to make ammonium nitrate, state two uses of ammonium nitrate. (1mk

(c) Nitrogen forms many compounds in which its oxidation state varies:(i) What is meant by oxidation state? (1mark)(ii) What is the oxidation state of nitrogen in Ca3N2. (1mark)

3. (a) Chlorine gas can be prepared in the laboratory by reacting Potassium Manganate (vii) with concentrated hydrochloricacid. `

(i) Name another suitable reagent that can be used (1mark)(ii) State the conditions necessary for (i) above. (1mark)(iii) State and explain what would happen if a dry piece of red litmus paper was dropped in a gas jar of dry chlorine.

(2marks)

Page | 187

Chemistry paper 1, 2&3 (b) Chlorine is a strong oxidizing agent. Write down an equation for the reaction of Chlorine with

(i) Hydrogen sulphide gas. (1mark)(ii) with iron (ii) chloride (1mark)

(c) Hydrogen Chloride gas is a colourless gas which dissolves readily in water forming hydrochloric acid.(i) At room temperature and pressure, 1.00dm3 of water dissolves 432 dm3 of hydrogen chloride gas. How many moles of

hydrogen chloride dissolves in 1dm3 water (1 mole at r.t.p. occupies 24.0dm3) (2marks)(ii) The hydrochloric acid formed has a volume of 1.40 dm3; calculate the concentration of the acid in mol/dm3. (1mark)(iii) In the solution, the molecules ionize as below

HCl(ag) → H+(ag) + Cl-(ag)

Describe a simple test to confirm presence of Cl- ions in the solution. (2marks)4. (a) Describe how a solid mixture of Zinc sulphate and lead (ii) Sulphate can be separated into Solid samples. (3marks)

(b) The table below shows the tests that were carried out on three portions of a compound and the results obtained.Study it and answer the questions that follow.

Test1. Addition of few drops of ammonium hydroxide to the first portion until

in excess2. Addition of few drops of acidified barium nitrate to the second portion3. Addition of few drops of Lead (ii) nitrate to the third portion.

ObservationWhite precipitate soluble in excess

White precipitate formed White precipitate formed.

(i) Identify the cation and anions present in the compound; (ii) Write an ionic equation for the reaction in the third portion. (1mark)

(c) Consider the flow chart below; use it to answer the questions that follow.

Conc HNO3(aq) Solution H, brownSolid F

gas

Few drops of NH3(aq)

Blue precipitate

Excess NH3(aq)

Deep blue solution N

(i) State the most likely identity of solid F. (1mark)(ii) Write the chemical equation for the reaction between solid F and concentrated nitric (v) acid. (1mk)(iii) Name

(A) Solution N (1mark)(B) Solution H (1mark)

(iv) Write the formula of solution N. (1mark)5 (a) (i) What is an electrolyte? (1mark)

(ii) State how the following substances conduct electricityI Molten Calcium Chloride (1mark)II Graphite (1mark)(b) the standard electrode potentials for certain half cell reactions are shown below.

W2+(aq) + 2e- → W(s) - 0.76VX2+(aq) + 2e- → X(s) - 0.23VY+(aq) + e → Y(s) + 0.80vZ2+(aq) + 2e- → Z(s) + 0.34v

(i) Identify the strongest oxidizing agent. (1 Mk)(ii) Write the cell equation for a cell formed by connecting W and X cells. (1 mark)(iii) Calculate the e.m.f of cell in a(ii) above. (1 Mk)(c) During electrolysis of silver nitrate, a current of 0.5A was passed through the electrolyte for 3 hours.(i) Write the equation for the reaction which took place at the anode. (1 Mk)(ii) Calculate the mass of silver deposited. (Ag = 108, IF = 96500C) (2 Mks)

Page | 188

Chemistry paper 1, 2&3 (iii) Give two reasons why it is necessary to electroplate iron with silver. (2 Mks)

6.

Volume of NaOH 0 5 10 15 20 25 30 35Volume of acid + NaOH mixture in cm3 20 25 30 35 40 45 50 55Temperature (oC) 21.0 22.0 23.0 24.0 25.0 25.0 24.0 23.0

(a) Plot a graph of temperature (y-axis) against volume of sodium hydroxide. (3 marks)(b) From the graph determine the:

(i) Highest temperature reached. (1 mark)(ii) Lowest temperature. (1 mark)(iii) Change in temperature (ΔT) (1 mark)

(c) Determine the volume of sodium hydroxide required to neutralize 20cm3 of 0.5M ethanoic acid. (1 mark)(d) Calculate the heat change given specific heat capacity = 4.2KJ/g/K and the density of solution mixture = 1g/cm3. (2 marks)(e) Calculate the number of moles of ethanoic acid used in the experiment. (2 marks)(f) Calculate the molar heat of neutralisation for the above reaction. (2 marks)

7. (a) Draw the structural formula of the following compounds:-(i) 2 - melthylhex -l-ene (1 marks)(ii) Butan -l-ol (1 Mk)

(b) Two methods of preparing alkenes are shown by the following general equations.(i) Alkanol Al203, 400oC Alkene(ii) Alkane Catalyst Alkene

heatWhat type of reactions are described by equations;(i)and (ii) (2 marks)

(c) Which of the two methods is used on a large scale. (1 Mark)(d) Pentanoic acid reacts with butan - 1 - 0l to form an organic compound.

(i) Write an equation to show the above reaction. (1 Mark)(ii) What is the name given to the above type of reaction? (1 Mark)(iii) A few drops of a certain catalyst must be added to the mixture to increase the rate of the reaction.

(A) Name the catalyst. (1 Mark)(B) Explain the role of the catalyst in the above reaction. (1 Mark)

(e) Draw the structure of;(i) Soapless detergent. (1 Mark)(ii) Soapy detergent. (1 Mark)

(f) Differentiate between a monomer and polymer. (2 Marks)

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Chemistry paper 1, 2&3 GATUNDU SUB-COUNTY SECONDARY SCHOOL JOINT EXAMINATION CHEMISTRY CONFIDENTIAL In addition to the fittings and chemicals found in a chemistry laboratory, each candidate will require the following:

1. About 120cm3 of solution K2. About 150cm3 of solution N.3. About 90cm3 of solution B.4. Solid D about 0.5g5. About 1.0g of solid E.6. About 0.2g of solid sodium hydrogen carbonate.7. 100ml measuring cylinder.8. Two 100ml beakers.9. Plain paper.10. Stop watch.11. 10ml measuring cylinder.12. 250ml volumetric cylinder.13. About 500ml of distilled water.14. One label.15. One 0-50ml pipette.16. One 25ml pipette.17. One pipette filler.18. Two 250ml conical flasks.19. Phenolphthalein indicator.20. 6 dry test tubes.21. One boiling tube.22. Two filter paper.23. Filter funnel.24. Metallic spatula.

Access to:-1. Bunsen burner.2. 2M sodium hydroxide solution supplied with a dropper.3. 2Mammonia solution supplied with a dropper.4. 2M sodium sulphate solution supplied with a dropper.5. 2M Nitric (v) acid supplied with a dropper.6. Acidified potassium dichromate (vi) solution.7. Acidified potassium manganate (vii) solution.

PREPARATIONS 1. Solution k is prepared by dissolving 20g of sodium thiosulphate in 700cm3 of distilled water and diluting to 1 litre. 2. Solution B is prepared by dissolving 8g of sodium hydroxide in 800cm3 of distilled water and diluting to one litre. 3. Acidified potassium manganate (vii) is prepared by dissolving 6.0g of potassium manganate (vii) in about 100cm3 of 2M

sulphuric (vi) acid, adding 800cm3 of distilled water and diluting to one litre of solution. 4. Solid D is a mixture of ZnCO3 and Al(NO3)3 in the ratio 2 : 15. Solid E is about 0.5g maleic acid6. Solution N is 2M HCl

Page | 190

Chemistry paper 1, 2&3 GATUNDU SUB-COUNTY SECONDARY SCHOOL JOINT EXAMINATION 233/3 CHEMISTRY PAPER 3 PRACTICAL JULY/AUGUST 2016 2 ¼ HOURS

1. You are provided with:- Solution K A monobasic acid solution N. Sodium hydroxide solution B prepared by dissolving 8g of sodium hydroxide in 1 litre of distilled water.

You are required to determine:- The rate of reaction between solution N and solution K The molarity of the monobasic acid solution N.

PROCEDURE 1 Using a measuring cylinder, measure 20cm3 of solution k into an empty 100cm3 beaker. Place it on a mark ’X’ on a white plain paper. Rinse the measuring cylinder and use it to measure another 20.0cm3 of solution N. Add solution N into solution K and start off the stop watch. Then record the time taken for the mark ‘X’ to become invisible from above. Repeat the procedure by measuring 17.5cm3 of solution N and adding 2.5cm3 of water and complete the table 1

Table 1 Experiment 1 2 3 4 5Volume of solution K (cm3) 20 20 20 20 20Volume of solution N (cm3) 20.0 17.5 15.0 12.5 10.0Volume of water (cm3) 0.0 2.5 5.0 7.5 10.0Time taken for x to become invisible(sec)1/time (sec -1)

(5 Marks)(a) Draw a graph of reciprocal of time (1/t) against volume of solution N. (3 Marks)(b) From the graph:(i) Determine the time taken for the cross ‘X’ to be invisible at 16.5cm3 of solution N (2marks)(ii) Determine the rate of reaction when 16.5cm3 of solution N is used. (1Mark)

PROCEDURE 11 Measure 50cm3 of solution N into a 250ml volumetric flask. Add more distilled water to make 25.0cm3 of solution. Label this as solution J. Fill a burette with solution J. Using a pipette and pipette filler, place 25.0cm3 of solution B in to a 250ml conical flask. Add two to three drops of phenolphthalein indicator. Titrate solution B against solution J until the pink colour disappears. Record your results in table 2 below. Repeat the titration two more times and complete the table. Table 2.

I II IIIFinal burette reading Initial burette reading Volume of solution J used (cm3)

(4 Marks) (a) Determine the average volume of solution J used. (1 Mk)(b) Determine the number of moles of;

(i) Sodium hydroxide in 25.0cm3 of solution B. (1Mark)(ii) The monobasic acid solution J in the average titre. (1 Mark)(iii) The monobasic acid solution J in 250.0cm3 of the solution. (1 Mark)

2. You are provided with solid D. Carry out the following tests and write your observations and inferences in the spacesprovided.

(a) Place all of solid D in a boiling tube. Add about 6.0cm3 of distilled water and shake thoroughly. Filter the mixture into a testtube. Dry the residue using pieces of filter papers. Retain the residue for use in test 2 (b) below. Divide the filtrate into threeportions

Page | 191

Chemistry paper 1, 2&3 (i) To 2cm3 of the filtrate, add sodium hydroxide solution drop wise until in excess.

Observations Inferences(1mk) (1mk)

(ii) To 2cm3 of the filtrate, add one to two drops of sodium sulphate solution.Observations Inferences

(1mk) (1mk)(iii)To 2cm3 of the filtrate, add aqueous ammonia drop wise until in excess.

Observations inferences(1mk) (1mk)

(b) (i) Put a spatula end full of the residue obtained in (a) above in a test tube. Add about 6cm3 of nitric (v) acid into the test tube.Retain the mixture for tests b(ii) and (iii) below.

Observations inferences(1mk) (1mk)

(ii) To 2cm3 of the mixture obtained in b(i) above, add aqueous sodium hydroxide drop wise until in excess.Observations inferences

(1mk) (1mk)

(iii)To 2 cm3 of the mixture obtained in b(i) above, add aqueous ammonia solution drop wise until in excess.Observations inferences

(1mk) (1mk)3. You are provided with solid E. Use it to carry out the tests below. Write your observations and inferences in the spaces

provided.(a) Place one third of solid E on a metallic spatula and burn it using a Bunsen burner.

Observations Inferences(1mk) (1mk)

(b) Place the remaining solid E in a test-tube. Add about 6cm3 of distilled water and shake the mixture.(i) To 2cm3 of the mixture, add a spatula end full of solid sodium hydrogen carbonate.

Observations inferences

(1mk) (1mk)(ii) To 2cm3 of the mixture, add 2cm3 of acidified potassium dichromate (vi) and warm.

Observations inferences(1mk) (1mk)

(iii) To 2cm3 of the mixture add two drops of acidified potassium manganate (vii) and shake well.Observations inferences

(½mk) (½mk)

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Chemistry paper 1, 2&3 GATUNDU SOUTH FORM FOUR EVALUATION 2016 233/1 CHEMISTRY PAPER 1 THEORY JULY / AUGUST 2016

1. (a) Ionisation energy - is the energy required to remove one mole of electrons from one mole of atoms in gaseous state 1while electron affinity is the energy required by an atom to acquire an electron in the outermost energy level in gaseousstate 1

(b) R is higher / greater ½ that Q because Q is a smaller atom therefore its nucleas ½ attracts electrons strongly.2. 10 R 11R

5 5

X x 10 + 100 - x 11 = 10.28 1100 100

x x 10 + 100 - x x 11 =10.28100 100

100 ( x/10 )100 + x (1 - x/100 ) x 11 = 10.28 x 100 10x + ( 100 - x ) 11 = 1028 10x + 100 - 11x = 1028 1 10x - 11x = 1028 - 1100

+ x = + 72 (i) x = 72% ½(ii) 100 - x = 100 - 72

x = 28% ½10R x = 72% 5

11R y = 28% 5

3 (a) i and (ii)

(iii) A ½ and C ½ 4. Since AlCl3 sublimes 1 and NaCl does not sublime sublimation process will separate the two.

Heat the mixture, aluminium chloride sublimes 1 into vapour and forms the sublimate on the cooler parts of heating tube sodium chloride will remain 1 at the bottom of the heating tube.

5. (a) X = 12 = 2.8.2 1(b) W and Y 1(c) (i) Z 1 = 17 = 2.8.7. because its has 7 electrons 1 in the outermost energy level.

(ii) Ionic bond 16. (a) Potassium bromide 1

(b) 60 - 58 = 2g 1(c) Fractional crystallization 1

7.When hot When coldYellow ½ White ½red ½ Yellow ½

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Chemistry paper 1, 2&3 8. (a)

(b) Use a measuring cylinder 1 instead of a gas jar to measure the volume of water displaced by the used air9. (a) Identify the solid

H - Carbon (IV) oxide1J - Calcium oxide 1

(b) - Acid soils are improved by addition of quick lime - CaO- Drying agent 1

10. (a) Monoclinic sulphur 1Or

Rhombic sulphur 1 (b) Uses of sulphur

- Manufacture of sulphuric (VI) acid 1 - As a fungicide 1 - In the manufacture of bleaching agents. 1 - Vulcanisation ( hardening of oils to fats ) 1 - Manufacture of dyes & fireworks when used in small quantities. 1Any 2 correct

11. (a) chlorine 1 - This is because oxidation number of chlorine reduces from 10 to -1 showing that it has be reduced by iron (II) chloride. Or it oxidizes iron (II) to iron (III) ClO 4 - x + 4 ( -2) = -1

x - 8 =-1 x - 8 -1 x = + 7 1

12. (a) The Ca2+ or Mg2+ ions in the hard water were trapped in the permutit containing Na+ ions 1 (b) By passing brine (concentrated sodium chloride ) 1 through the column. (c) - Strengthening bones and teeth 1Or - Used also in beer brewing

13. (i) At the beginning the graph is steepest because the rate of reaction is high due to the high concentration of the reactants(reactants not used up)

(ii) AB - Marks the end point of the reaction i.e reaction has ended / one of the reactants is used up

14. (a) To increase surface area of dissolving 1 / also avoid sucking back of the gas.(b) The pH value is above 7 because ammonia is a basic gas and when dissolved in water forms a basic solution

Bases have a pH value above 7. (c) Water is a polar solvent while methylbenzene is non-polar and water therefore has some attraction to the polar

hydrogen chloride and therefore dissociates. HCl Does not dissociate in methyl-benzene // HCl is ionic in water butmolecular in methyl-benzene.

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Chemistry paper 1, 2&3 15. RO2 = RMMSO2 = Time SO2 1

RSO2 RMMO2 Time O2

R.M.M of SO2 = 32 + 32 = 64 y = 141.42 seconds 1O2 = 16 x 2 = 32

64 = y32 100

y x 32 = 100 64 1 accept alternative method32 32

16. (i) Mass of M = 10.352g10.240g0.112g 1

(ii) Mass of oxygen = 10.400g- 10.352g

0.048g 1(b) Empirical formula

Element K OMass 0.112g 0.048Moles 0.112 0.048

56 16

Moles 0.002 0.003 10.002 0.0021 x 2 1.5 x 2

Ratios 2 3E.F K2O3 1

17. (a) P - Sodium ethanoate 1Q - Methane 1

(b) Substitution 118. (a) Ag (S) → Ag+ (aq) + e-

(b) At the cathode the spoon is coated by silver 1 silver ions receive electrons to form silver metalthat forms silver coating. 1

19. (a)Advantage Disadvantage

R - COO - Na + They are cheaper ½ compared to soapless Forms scum with hard water ½detergent

R - SO3 - Na + They don’t form ½ scum with Mg2+ & Ca2+ Made from petroleum products orvegetable oils which are expensive ½

(b) B = R - OSO3 - Na+ 1 - Because it does not form scum with hard water 120. (a) (i) Pb 2+ 1

(ii) (Cl -) 1(b) Ag + (aq) + Cl - (aq) → Ag Cl (s) 1

21. (a) Chlorine gas 1(b) - Greenish - yellow gas

- Unpleasant chocking smell- Denser than air- Fairly soluble in water Any 1 1

(c) Blue litmus paper turned red½ then to white. ½22. (a) The negative sign indicates / shows that the reaction is exothermic / evolves heat 1

(b) (i) Brown colour intensifies / persists 1(ii) Shift the equilibrium to the left because i.e brown colour intensifies 1 Increasing volume decreases pressure and hence favours backward reaction.

23. (a) Wood ash is basic. It would therefore react with aluminium oxide coating on aluminium Utensils which is amphoteric. 1

(b) (i) Its strong 1(ii) Not easily corroded 1(iii) Its light 1 Any 2

24. Energy of reactantsCH4 (g) +2 Cl2 (g) → CH2 Cl2 (g) + 2HCl (g)

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Chemistry paper 1, 2&3 H H

H C H +2 Cl Cl H C Cl + 2 H Cl √1 mark

H Cl414 x 4 + 2(244 ) = 4141 x 2 +2 (326) + 2(431) √1mark

2144 = 2342Energy consumed energy produced

2144 - 2342 = -198 kJ /mole√1mark

25. (NH2)2CO = RMM =2 x 14 + 4 x 1 + 12 x 1 + 16 x 1

28 + 4 + 12 + 1632 + 28

= 602NH3 (g) + CO2 (g) →(NH2)2 CO (aq) + H2O (l)

620kg 1 mole36, 470.588 molesMass = 620 x 1000

= 620,000gMoles = 620,000

17= 36,470.588 moles 1Moles of (NH2)2 CO = 36,470.588

2= 18,235.29 moles 1

Mass = moles x RMM= 18,235.29 x 60= 1,094,117.65g= 1094.118kg 1

26. (a) N2O(b) Al2 O3

(c) Amphoterism27. 2: 6

28. Used for lighting purposes

accept alternative method

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Chemistry paper 1, 2&3 GATUNDU SOUTH FORM FOUR EVALUATION 2016 233/2 CHEMISTRY PAPER 2 THEORY

1.

2.

3.

4.

(b)

(c)

a. (i) v, 1/2 has the biggest atomic radius, hence its outermost electron is loosely held ½(ii) s.(iii) Alkaline earth metals(iv) s is smaller ½ , has more electrons in the outermost energy level hence greater nuclear attraction. ½(v) Q, ½ has 4e in the outermost energy level hence requires a lot of energy to transfer elections ½(vi) formula TU2

Bond ionic/electrovalent.(vii) s is ½ more reactive, Has a smaller atomic radius, hence attracts electrons much more readily ½

(a) (i) Method of ½ collection should be collected by upward ½ delivery because ammonia is less dense than air.(ii) Calcium oxide √ 1(iii) Ca (OH)2(s) + 2NH4Cl(s) →

CaCl2(ag)

+ 2NH3(g)

+ H2O(1)

½ correct equation½ penalize ½ for missing state symbols.

(iv) Insert a red litmus paper into the gas jar containing ammonia gas.The red litmus paper turns blue indicating the presence of ammonia.Alt: Insert a glass rod into concentrated hydrochloric acid and bring it to the mouth of the gas jar containingammonia gas.White dense fumes indicate the presence of ammonia gas.

(b) (i) Platinum catalyst.(ii) 4NH3(g) + 502(g) → 6H20(l) + 4NO(g)

(iii) As a fertilizerMaking of explosives.

(c) (i) It is the apparent charge that an atom have in molecules/ions.2 x 3 + 2N = 06 + 2N = 0

2N = -6N = -3

A (i) Pb02, Mn02

(ii) Heat.(iii) The red litmus remains red.

Because the dry chlorine does not breach.

B. (i) H2S (g) + Cl2(ag) → 2HCl(g) + S(s)

(ii) 2FeCl2(ag) + Cl2(g) → 2FeCl3(ag)

C (i) 24dm3 = 1 mol32dm3 = 1 x 432 = 18 moles

24

(ii) 1.40dm3 = 18.0 moles1dm3 = 18 x 1 = 12.86 M

1.4(iii) Add a few drops of acidified AgN03or acidified

Pb(NO3)2 in a test tube containing Cl- ionsA white precipitate is formed.In Pb(NO3)2 the precipitate dissolve on warming

(a) Add water to the mixture, stir to dissolve zinc sulphate, filter to obtain lead (ii) sulphate as the residue, evaporate the filtrate to saturation and cool for zinc sulphate crystals to form.(i) Cation zn2+

Anion: SO42-

(ii) Pb2+(ag) + SO42-(ag) → PbSO4 (s)

(i) Copper.(ii) Cu(s) + 4HNO3(a) → Cu(NO3)2(ag) + 2NO2(g) + 2H2O(1)

(iii) Solution N - Tetra amine Copper (ii) ionsSolution H - Copper (ii) nitrate

2+ (iv) Cu(NH3)4 (aq)

5. (a) (i) a substance in moltenor aqueous state that allows the passage of an electric current and is decomposed by it.(ii) I - by movement of ions

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Chemistry paper 1, 2&3 II - by used of decocalised electrons

(b) (i) Y(ii) W(s) + X2+ → X + W2+

(iii) E.m.f = E reduced - E oxidized= (-0.23) - (0.76)= -2.53v

(c) (i) 4OH- → 2H2O(1) + O2 + 4e-

(ii) Ag = 108, IF = 96,500CQ It = 5 x 3 x 60 x 60 ½ = 54,000C 1√

108g = 96500C?g = 54,000C108 x 545000½ = 60.43 ½

96500(iii) To improve the appearance

Prevent iron from rusting.6. (a) P - 1 C - 1 scale - 1

(b) (i) Temperature obtained after extrapolation ie 25.5oC(ii) 21.0oC(iii) ΔH = (highest - lowest)

= 25.5 - 21.0 = 4.5oC (c) 22cm3

(d) Total volume = 20 + 22.0 = 42.cm2

Mass of the solution = 42 x 1g/cm3 = 42g. Heat charge H = MC ΔT ΔH = 4.2 x 42 x 4.5 = 793.8 J

(e) Moles = volume in litres x molarity 20dm3 x 0.5 mol/dm3 = 0.01

1000 (f) NaOH + CH3 CooH → CH3COONa + H2O(l)

1000cm3 → 0.5 moles20 cm3 → 0.01 moles

0.01 moles → 0.7938 kj/mol1 mole → 1 x 0.7938 kj/mol = 79.38 kj/mol

0.01 7.

(b) (i) Dehydration (ii) Cracking

(c) Cracking acc II (d) (i)

(ii) Esterification (iii) (a) Concentrated sulphuric (vi) acid. (b) Speed up the rate of reaction by lowering the activation energy.

(e) (i) R 0S03- Na+

(ii) R - COO- Na+

(f)Difference between monomer and polymer

Moner PolymerUnsaturated Saturated 1Small molecule Large molecule 1Have gaseous or liquid state Solid state 1

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Chemistry paper 1, 2&3 GATUNDU SUB-COUNTY SECONDARY SCHOOL JOINT EXAMINATION 233/3 CHEMISTRY PAPER 3 PRACTICAL JULY/AUGUST 2016 2 ¼ HOURS

1. PROCEDURE 1.

TABLE 1 ………………………………………………… (5 Marks)I. Complete table …………………………………………… (2 Marks)

Recording time taken…………………………………… (1mark)Penalties.

(i) Penalize ½ mk once for any space not filled subject to at least 4 readings being given otherwise penalize fully. (ii) Panalise ½ mk for unrealistic time reading i.e below 40 seconds or above 150 seconds.

Calculating 1/time ………………………………… (1 Mark)Penalties

(i) Penalise ½ mk once for any 1/time not calculated. (ii) Answer given must be correct to 4 decimal places unless it works out exactly to a lesser decimal place otherwise penalise ½

mk once. II. Use of decimal (subject to at least 2 readings) …………… (1 Mark)

Award 1mk if the decimal in time taken is consistent otherwise penalise fully. III. Accuracy ……………. (1 mark)

Compare the candidates time readings in experiment 1 to the school value and award 1 mk if the reading is within +5 seconds of school value (s-v) otherwise penalise FULLY. NB: school value (s.v) is the teachers value.

IV. Trends …………..(1mk) Award 1 mk for a continuous rise in time taken otherwise penalise fully. GRAPH …………… 3 MKS

I. Correct labeling of both axes …………….. ½ mkPenalties.

(i) Penalise FULLY for inverted axes. (ii) Penalise FULLY for wrong units used otherwise ignore if units are omitted. (iii) Panalise FULLY if only one axis is labeled II. Scale …………………. ½ mk

Conditions. (i) Area covered by plot should be at least half of the grid provided. (iv) Scale interval should be consistent on each axis. (v) Scale chosen must be able to accommodate all plots/points whether plotted or not. (check the range of the reading on the

table) NOTE: Penalise FULLY if any of the above conditions is not met.

III. Plotting ………………………………… 1 mk (i) If 5 points are correctly plotted award 1mk (ii) If only 4 points are correctly plotted award ½ mk. (iii) If less than 4 points are correctly plotted award 0mk

NOTE: (a) If the scale intervals change, mark plots (if any) within the first scale and treats the rest as wrong. (b) Accept correct plots even if the axes are inverted and award accordingly. IV. LINES/SHAPE ……………………….. 1MK (a) Accept a straight line for one mk otherwise penalise fully. (b) (i) Accept correct showing on the graph for 1mk and correct reading for one mk.

(ii) Rate of reaction = 1/time at 16.5cm3

PROCEDURE II Table 2.

A. Complete table ………………………………………………….. (1 Mk) Conditions

(i) Complete table with 3 titrations…………………… (1 Mks) (ii) Complete table with 2 titrations…………………… ½ Mks) (iii) Complete table with 1 titrations……………………(0 Mks)

Penalties (i) Wrong arithmetic. (ii) Inverted table.

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Chemistry paper 1, 2&3 (iii) Burette readings beyond 50ml and unexplained. (iv) Unrealistic litre below 1.0ml or hundreds.

Penalise ½ mk for each to a maximum of ½ mk. B. Use of decimal (Tied to 1st and 2nd row only) …. 1 mk

Conditions. (i) Accept either 1 or 2 decimal points used consistently otherwise penalise fully. (ii) If 2 d.p is used, then the 2nd d.p must be ‘0’ or ‘5’ otherwise panalise fully. C. Accuracy (Tied to correct titre value) ……………. 1 mk

Compare the candidates’ titre values with school value and award marks as follows. (i) If at least one is within + 0.10 of SV award …………. 1 Mk (ii) If non is within +0.10 but at least one is within + 0.2 of SV award ………….. ½ mk (iii) If no value is within + 0.20 of SV award ………. 0mk D. Principles of averaging ……………….. 1mk

Conditions. (i) If 3 consistent values are averaged ………….. (1 mk) (ii) If 3 titrations done but only 2 are consistent and averaged award ………………….. (1 Mk) (iii) If only 2 titrations done and are consistent and are averaged award ……………….. 1 mk (iv) If 3 titrations are done but inconsistent and are averaged award ……….. 0 mk (v) If 3 titrations done and all can be averaged, but only two are averaged award …………… 0 mk (vi) If 2 titrations done are inconsistent and averaged award …………. 0 mk (vii) If only one titration done …………………………………. (0 mk) E. Final accuracy (Tied to correct average titre)….. (1 Mk)

Compare the candidate’s average titre with s.v (i) If within + 0.1 of s.v award …………………(1 Mk) (ii) If not within + 0.1 but within + 0.2 of s.v ………….. ½ mk. (iii) If not within + 0.2 of s.v award …………. 0 mk

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Chemistry paper 1, 2&3 KERICHO SUB - COUNTY JOINT EVALUATION. 233/1 (THEORY) JULY/ AUGUST 2016 CHEMISTRY PAPER 1

1. a) The figure below shows some changes in state for a substance X. Study the diagram and answer the questions.

Each of the changes can be speeded up by heating or by cooling. Which changes are speeded up by cooling and whichones by heating. (2marks)

b) Magnesium sulphate may be used as a laxative. What does this term laxative mean? (1mark)2. Both molten sodium chloride and molten sodium metal conducts electricity. Explain how each of these conducts electricity

(i) Molten sodium chloride (1mark)(ii) Molten sodium metal (1mark)

3. Study the flow chart below and answer the questions that follow.

(a) Name the substance (1mark)(i) A(ii) B(b) State the property of S02 exhibited in step 2. (1mark)

4. Study the energy level diagram below and answer the questions that follow.

(i) State and explain whether the reaction represented is endotherrnic or exothermic. (1 mark)(ii) From the diagram, determineI. the activation energy (1 mark)

II. enthalpy of reaction (1 mark)5. The following chromatogram was obtained in an experiment to investigate the components present in certain dyes.

a) Which two dyes when mixed would produce A? (1 mark)b) Which dye is pure? (1 mark)

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Chemistry paper 1, 2&3 c) Indicate on the diagram the solvent front. (1 mark)

6. Two elements X and Y are represented as shown below17X and 20Yi) Write the formula of the compound formed when X and Y react. (1mark)ii) State the family name to which element X belongs. (1mark)iii) Element Y has a mass number of 40, how many neutrons are present in its nucleus? (1mark)

7. a) State Graham’s law of diffusion. (1mark)b) If it takes 30 seconds for 100cm3 of carbon IV oxide to diffuse across a porous plate, how long will it take 150cm3 of

nitrogen IV oxide to diffuse across the same plate under similar conditions? (C = 20, N=14, O=16) (2marks)8. a) Give the IUPAC names of the following compounds (2marks)

i) CH3(CH2)OHii) CU3CH2CH(CH3)COOHb) Given the following polymer, draw the structure of the monomer. (1 mark)

9. In an experiment, rods of metal X, Y, Z were cleaned with sand paper and placed in a beaker containing water. Another set ofrods was also placed in a beaker containing dilute acid. After placing the rods in the two liquids, bubbles of gas were seenaround some of the rods as shown in the diagram below.

a) Why is it necessary to clean the rods with sand paper before dipping them into the liquid. (1 mark)b) Arrange the three metals in order of their reactivity starting with the most reactive. (2 marks)

10. The grid below is part of periodic table. Use it to answer the questions that follow. (The letters do not represent the actualsymbols of the elements)

R S

N Q T U

P

a) Indicate in the grid the position of an element represented by letter V, whose atomic number is 14. (1mk)b) Select a letter which represents a mono atomic gas. (1 mark)c) Write an equation for the reaction between Q and T. (1 mark)11. The set up below shows how gas A, was prepared and reacted with heated magnesium

a) Give a reason why it is not advisable to heat magnesium before heating ammonium nitrite. (1 mark)b) i) Identify gas A. (1mark)

ii) Write a chemical equation for the reaction between gas A and magnesium. (1mark)

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Chemistry paper 1, 2&3 12. Radioactive polonium - 216 decays as shown below.

Determine the value of m and n. (1 ½ marks)b) The table below gives the rate of decay of a radioactive element Y.

Number of days Mass in g0 48

270 1.5

Calculate the half-life of the radioactive element Y. (1 ½ marks)13. Study the table below and use it to answer the question that follow

Solution PHA 3.5B 14C 8.5

i) In which of the solution will phenolphthalein indicator be colourless. (1mark)ii) Which of the solutions could be used to relieve heartburn ? Explain. (2marks)

14. Given the following reagents; solid sodium carbonate, solid lead (II) nitrate, water. Describe how a sample of lead (II)carbonate can be prepared in the laboratory.(3 marks)

15. The table below shows the tests carried out on separate sample of water drawn from a well and the results.

Test Resultsi) Addition of excess aqueous ammonia White precipitate

ii) Addition of a few drops of dilute sulphuric VI acid No precipitate formediii) Addition of dilute hydrochloric acid followed by few White precipitate

drops of barium chloride

a) Identify the possible cations and anions present in the water. (2marks)Write an ionic equation for the reaction which takes place in test tube (iii). (1mark)

16. a) A mass of 40g of a saturated solution of Potassium Chlorate at 250C yields 14 of Potassium Chlorate when evaporated todryness. Calculate the solubility OF Potassium Chloride at 250C

b) State one advantage of hard water. (1mark)17. a) Why is air considered as a mixture rather than a compound ? (1mark)

b) State one similarity between rusting and combustion of iron. (1mark)c) Explain why iron nails rust faster in sodium chloride solution than in tap water. (1mark)

18. The flow chart shows the extraction of zinc metal from its chief ore. Study the flow chart and answer (he questions thatfollow

a) Name the chief ore used in the process. (½ mk)b) Write equation for the reaction in the roasting furnace? (1mk)c) State the functions of the lead spray. (1mk)d) Give one use of zinc. (½ mk)

19. The apparatus shown below was used to investigate the effect of carbon II oxide on copper II oxide.

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Chemistry paper 1, 2&3 a) State the observation that was made in the combustion tube by the end of the experiment. (1 mark)b) Write an equation for the reaction that took place in the combustion tube. (1mark)c) Why is it necessary to burn gas coming out of tube K ? (1mark)20. When lOg of a mixture of potassium chloride and anhydrous sodium sulphate is dissolved in water and excess barium

chloride solution added. 6.9g of Barium sulphate is precipitated. Calculate the composition of the mixture. (K .= 39. Cl = 35.5, Na=23, O =16, Ba=137) (3marks)

21. When bismuth III Chloride is added to water, a reaction occurs and a white precipitate forms as shown below. BiCI3(aq) + H20(l) BiOCl(s) + 2HCl(aq)

What would be the effect on the amount of the precipitate formed if sodium hydroxide solution is added to the equilibriummixture ? Explain your answer. (2 marks)

22. The set up below was used to investigate some properties of chlorine gas.

a) Name :i) Substance G (1 mark)ii) A suitable drying agent. (1mark)

b) What property of chlorine make it possible for it to be collected as shown in the diagram? (1 mark)23. What volume of oxygen gas at r.t.p will be liberated at the anode when a current of 3 amperes is passed through magnesium

sulphate solution for 45 minutes and 30 seconds. (Molar gas volume at r.t.p = 24000cm3, Faraday constant = 96500Coulombs) (3marks)

24. a) What is air pollution ? (1 mark)b) State four gaseous substances present in unpolluted air. (2marks)

25. The labels of two reagent bottles contained the following safely symbols.

a) What do the symbols mean ? Explain. (2 marks)b) Which of the reagent is more harmful ? (1 mark)

26. The table below shows properties of some chlorides. Study it and answer the questions that follow.Chloride Mp(°C) BP (°C) Electrical conductivity in PH of solution

aqueous solutionAl - 183 Good 3

Na 860 1420 Good 7

P 32 75 Good 3

H -146 -29 Good 1

a) Explain the high melting and boiling points of sodium chloride. (1mark)b) Write an equation for the reaction between PC15 and water. (1mark)c) Draw the dot (•) and cross (x) diagram to show bonding in NaCl. (1 mark)27. The cell convention for and electrochemical cell is shown below.

Zn(s)/ Zn2+ (aq) // Pb2+ (aq) / Pb(s)

(a) Name two substances that can be used as electrolytes in the above cell. (1mark)(b) Which of the electrodes is the negative in the cell above ? Explain. (2marks)(c) Excess concentrated sulphuric VI acid was mixed with pieces of dry wood as shown.28. Excess Concetrated Sulphuric Vi acid with pieces of dry wood as shown

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Chemistry paper 1, 2&3 a) State the observation made in the tube. (1 mark)b) When the reaction was complete, the mixture was heated gently, then strongly and set up adjusted as shown below.

State and explain the observation made on acidified potassium chromate VI solution. (2 marks)

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Chemistry paper 1, 2&3 KERICHO SUB - COUNTY JOINT EVALUATION. 233/2 (THEORY) JULY/ AUGUST 2016 CHEMISTRY PAPER 2

1. Study the table below and answer the questions that follow. The letters do not represents the actual symbols of the elements

Formula of ion Electron configurationA2+ 2.8B3+ 2.8C- 2.8.8D- 2.8E2+ 2

a) Select elements found in:i) The same group (1 mark)ii) Period three (1 mark)iii) What is the family name given to the group to which elements identified in a(i) above belongs. (1 mark)

- How does the atomic radius of element B and A compare. Explain. (2 marks)- State two industrial use of element B. (2 marks)- With reason, compare the reactivity of C and D. (2 marks)- Write the formula of compound formed when A and D react. (1 mark)- What type of bond is formed when element E react with oxygen. Give a reason for your answer. (2 marks)2. The diagram below represents a set up that was used for electrolysis of aqueous copper (II) nitrate.

a) A gas that relights a glowing splint was produced at electrode A.i) Which electrode is the cathode ? Explain. (2 marks)ii) State another suitable method for collecting gas X. (1 mark)iii) Write ionic equations to show reactions that take place at the :

Anode (1 mark)Cathode (1 mark)

iv) Explain how the identity of the product at the cathode of this electrolysis can be confirmed. (2 marks)v) Calculate the mass of copper deposited if a constant current of 5 A was passed for 3 hours. (Cu = 63.5, IF = 965000)

(2 marks) 2.the following are standard electrode potentials for some electrodes. The letters do not represent the actual symbols of the

elements.

Element E° (volts)

A2+(aq) + 2e- A ( s ) -2.93B2+(aq) + 2e- B( s ) -2.38C2+(aq) + 2e- C( s ) 0.00D2+(aq) + 2e- D( s ) +0:3 4 VE+(aq) + e- E( s ) +2.87V

i) Which is the strongest reducing agent ? Explain. (2 marks)ii) Write the cell representation for the electrochemical cell obtained by combining the half cell of B and D. (1 mark)iii) Calculate the e.m.f of the cell in (ii) above. (2 marks)

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Chemistry paper 1, 2&3 3. Study the flow chart below and answer the questions that follow.

a) i) Name the type of reaction in the following steps :I. Step III (½ mark)II. Step IV (½ mark)ii) Name the important reagents and conditions in :

Step I: Reagent (1 mark)Condition Step II: Reagent (1 mark)ConditionStep V: Reagent (1mark)Condition

b) i) Write a balanced equation for the reaction taking place in :Step VI (1 mark)Step VII (1 mark)

ii) Give the systematic name of liquid X and substance LLiquid X (½ mark)Substance L (½ mark)

d) i) If the relative molecular mass of compound formed in step III is 42,000, determine the value of n in the compound.(C = 12.0, H = 1.0) (2 marks)

ii) State one disadvantages of continued use of items made from the compound formed in d(i) above. (1 mark)4. a) Define the following terms :

i) Atomicity (1 mark)ii) Molar gas volume (1 mark)

b) i) State Gay - Lussac’s law (1 mark)ii) A sample of 10cm3 of hydrogen sulphide was burned in 40cm3 of oxygen. Calculate the volume and composition of

residual gas (assume all volumes are measured at s.t.p) (2 marks)c) i) Calculate the mass of sodium carbonate contained in 200cm3 of 0.02M sodium carbonate solution. (2 marks)

ii) 0.239g of copper (II) oxide was placed in a conical flask. Calculate the volume of 0.1 M solution of hydrochloric acidthat would completely react with copper (II) oxide in the conical flask.(0= 16.0, Cu = 63.5, H= 1.0, Cl = 35.5) (2 marks)

d) Find the mass of 5.2 x 102'5 atoms of sodium. (Na = 23.0, L = 6.023 x 10 3) (2marks)5. a) Starting with lead (II) carbonate, describe how a solid sample of lead sulphate can be prepared. (3 marks)b) Water Was added to lead (II) nitrate by a student. She divided the resulting solution into four, state the observation made after

subjecting them to the following tests:i) To the first portion she added sodium hydroxide dropwise until in excess. (1 mark)ii) To the second portion she added ammonia solution dropwise until in excess. (1mark)iii) the third portion she added hydrochloric acid and warm. (1 mark)iv) To the last portion she added sodium iodide solution. (1 mark)v) Write an ionic equation for the reaction in test (iv) above. (1 mark)

c) State two commercial uses of sodium carbonate obtained in Solvay process. (2 marks)6. The following diagram was used to study a property of hydrogen gas. Study it and answer the questions that follow.

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Chemistry paper 1, 2&3 a) Name the missing condition in the above set up. (1 mark)b) Explain why the combustion tube is clamped in a slanting position. (1 mark)c) Before lighting the gas at the end of delivery tube, hydrogen must be let to pass through until all the air is driven out. Explain.

(1 mark)d) State three observations that occur in the combustion tube. (3 marks)e) Why was hydrogen gas burnt at point Z. (1 mark)f) Why should the supply of hydrogen gas be continued while the apparatus cool. (1mark)g) What would be observed if the experiment was repeated using lead (II) oxide. (1 mark)h) Other than the property investigated above, name two other chemical properties of hydrogen gas. (2 marks)i) State two industrial use of hydrogen gas. (2 marks)7. The extraction of aluminium from its ore takes place in two stages; purification stage and electrolysis stage. The diagram

below shows the set up for electrolysis stage.

a) i) Name the ore from which aluminium is extracted. (1 mark)Name one impurity which is removed at the purification stage. (1 mark)

b) i) Label bn the diagram each of the followingI. AnodeII. CathodeIII. Region containing the electrolyte (3 marks)ii) The melting point of aluminium is 2054°C but electrolysis is carried out between 800-900°C.I. Why is electrolysis not carried out at 2054°C (1 mark)II. What is done to lower the temperature? (1 mark)iii) The aluminium which is produced is tapped off as a liquid. What does this suggest about its melting point? (1 mark)

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Chemistry paper 1, 2&3 KERICHO SUB - COUNTY JOINT EVALUATION 233/3 (PRACTICAL) JULY/ AUGUST 2016 CHEMISTRY PAPER 3

1. You are provided with :- solution A, 0.15M solution thiosulphate- solution B, 2M hydrochloric acid- solution C, a solution of basic solution (0.2M X (OH)n)You are required to determine the rate of reaction between hydrochloric acid solution B at different concentrations of sodium thiosulphate solution A. Procedure 1 Draw a cross (x) on a piece of white paper using a pencil. Measure 30cm3 of a solution A using a' measuring cylinder and put it into a 100ml glass beaker placed over a white piece of paper drawn above. Measure 10cm3 of hydrochloric acid solution B using a 10ml measuring cylinder and add to the beaker, start the stopwatch. Immediately swirl the mixture. View the cross from above the mixture in the beaker. Stop the clock when the cross just disappears. Record the time taken in the table below. Repeat the above procedure using volumes of solution A, water and in the table below.

TABLEI

Experiment Volume of Volume of water Volume of Concentration ofsolution A (cm3) (cm3) solution B (cm3) solution A

(moldnV3)

1 30 0 10

2 25 5 10

3 20 10 10

4 15 15 10

5 10 20 10

6 5 25 10

a) Plot a graph (''I rate (S'1) against volume of solution A (cm3) b) From the graph determine :i) The rate of reaction when 19cm3 of solution A was used.ii) The time taken for X to disappear when 12cm3 of solution A was used. iii) Determine the time taken for X to disappear if 3cm3 of water was used. c) How does the rate of reaction relate to the concentrations of reagents ?

Procedure II

Time for X to Rate = (S-1)disappear(seconds)

(5 marks)

(3 marks)

(1 mark)(1 mark)(1 mark)(1 mark)

Using a clean 100ml measuring cylinder measure exactly 25cm3 of solution B into a 250cm3 volumetric flask. Add distilled water upto the mark. Labe this as solution D. Fill a burette with solution D. Using a pipette and a pipette filler place 25cm3 of solution C into a 250ml conical flask. Add two drops of methyl orange indicator and shake. Titrate it with solution D and record your results in table II. Repeat the titration two more times and complete the table.

Table II 1 II III

Final burette reading (cm3)Initial burette reading (cm3)

Volume of solution D added (cm3)

a) Determine the :i) average volume of solution D used. (1 mark)ii) moles of hydrochloric acid in solution D used. (2 marks)iii) moles of the alkaline solution C used. (1 mark)

b) Find the mole ratio for the reaction between solution A and solution C. (1 mark)c) Hence determine the oxidation state of metal x (1 mark)

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Chemistry paper 1, 2&3 2. You are provided with substance M for this question. Transfer the substance into a clean boiling tube. Add about 10cm 3 of

distilled water and stir. Pour the mixture into four clean test tubes of about 2cm3

Observations Inferences1 mk 1 mk

a) To the first portion of the solutions, add sodium hydroxide solution dropwise until in excess. Observations Inferences

1 mk 1 mk

b) Dip a clean stirring rod/ glass rod/ nichrome wire into the second portion and then place into the side of a blue Bunsen flame.Observations Inferences1 mk 1 mk

c) To the third portion, add 2-3 drops of barium nitrate solution followed by excess hydrochloric acid.Observations Inferences1 mk 1 mk

d) To the fourth portion, add 2-3 drops of acidified potassium manganate (VII) ObservationsObservations Inferences1 mk 1 mk

3. You are provided with substance W for tests in this question.a) Place 3 drops of substance W on a clean dry watch glass and ignite it.

Observations Inferences1 mk 1 mk

b) Place about 2cm3 of substance W in a clean dry test tube, then add all the sodium hydrogen carbonate provided.

Observations Inferences1 mk 1 mk

c) Place about 2cm3 of substance W in a test tube then add about lcm3 of acidified potassium manganate (VII) and warm themixture.Observations Inferences1 mk 1 mk

d) Place about 2cnr of substance W in a test tube then add 2-3 drops of bromine water.

Observations Inferences(1 mk) (lmk)

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Chemistry paper 1, 2&3 KERICHO SUB - COUNTY JOINT EVALUATION 233/1 JULY/ AUGUST 2016 CHEMISTRY PAPER 1 MARKING SCHEME

1. a) Cooling - III, IV, VIHeating - I, II, V

b) A laxative is a drug used to cause one to empty his bowels

2. i) Mobile ionii) Delocalised electrons

3. a) i) A - H2S03 - sulphuric IV acidB - K2SO3 - potassium sulphite

b) Oxidising property4. i) Exothermic; products at lower energy level than the

reactantsii) Activation energy = 6 0 - 4 0 = 20Kjmol Enthalpyof reaction = 2 0 - 4 0 = -20Kjmol

5. a) C and Db) Bc) On the diagram above top spots

6. i) YX2

ii) Halogensiii) 40- 20 = 20

7. a) Under the same conditions of temperature andpressure, the rate of diffusion of a gas is inversely proportional to the

square root of its densityb) RCQ2 = √

RNO2 MCO2

3.33 = √RN02 44

3.331.0225 = 46.058 se

8. a) i) Propan-l-olii) 2-methybutanoic acid

b)

9. a) To remove oxide coating which could inhibitreactionb) YZX - reactivity decreases

10. a) On the grid - group (IV) period 3b) Uc) Q(s)+ T2(S) QT2(S)

11. a) Magnesium would react with air in the combustion tube since nitrogen gas has not yet been produced b) i) Nitrogen gas

ii) 3Mg(s) + N2(g) Mg3N2(s)

12. a) 216 - 2 0 8 = 88 = 4m + 0m = 8/'4 = 2, a ( He)84 = 82 + 4 + n84 = 86 + nn = 84 - 86n = -2

n = 2 ( )48 - 24 - 12 6 3 1.55

=54 days

13. i) Aii) C - it is weakly alkaline hence neutralise excessacid in the stomach safely

14. - add enough water to Pb(N03)2 to form a solution- add enough water to Na2C03 to form a solution- mix the two solution to form PbC03 precipitate- filter the mixture to obtain PbC03 as residue- rinse the PbC03 with distilled water and- dry between filter paper

15. a) Al3+, S02-4

b) Ba2+(aq) + SO2- 4(aq) BaS04(s)16. a) Mass of KC103 = 14g

Mass of water = 26g14g of KCIO3 26g of water

l00g of water14 x 100 = 53.846g/100g of water

26b) Ca2+ are useful for development of strong bones and teeth

17. a) Can be separated using physical means b) Both processes uses oxygen in the reaction c) Sodium chloride is a substance that accelerate

rusting while tap water contains moisture andoxygen conditions necessaryfor rusting to occur

18. a) Zinc blendeb) 2ZnS(S) + 302(g) → 2ZnO(S} + 2S02(g)c) - prevents reoxidation of zinc

-condense zinc vapourd) -making dry cell causing

-making brass-galvanising iron sheets-manufacture of paints

19. a) Black solid change to brownb) CuO(S) + CO!g) → Cu(s) + C02(g)c) CO is poisonous when inhaled

20. Na2S04(S) + BaCl2(aq) BaS04(S) + 2NaCl(aq)

Moles of BaS04 = 0.02961 moles233

Mass of Na2S04 = 0.02961 x 142 = 4.2046Mass of KC1 = 10--4.2046

= 5.7954g21. Increased - HC1 is used thus the rate of forward

reaction is favoured or NaOH neutralise HC1, hence reaction proceeds faster in forward reaction to produce more HC1

22. a) i) Concentrated HC1ii) Concentrated sulphuric (VI) acid

b) It is denser than air23. 40H (aq) 4e

4F produces 1 mole of O? of 24000cm3 4x 96500C = 38600C produces 24000cm3

Q= It3 x 145 x60 + 30 = 8190C= 386000C produces 24000cm3 02 8190C produce81900 x 24000386000= 509.2227cm3 o f O 2

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Chemistry paper 1, 2&3 24. a) Addition of undesirable substances to the air

b) Oxygen, nitrogen, carbon (IV) oxide inert gases 25. a) A - toxic

-is poisonous and cause death if swallowed B - irritant -may cause blisters and if inhaled cause coughing

b) Reagent in bottle A 26. a) Giant ionic structure with strong ionic bonds

between particles b) PC15(S) + 3H20(1) H3P04(aq) + 5HC1(aq)

27. a) Soluble salts of the two salts b) Zinc loses electrons (oxidation) as Zn2+ ions goes into

solution leaving electrons on the zinc rod making it negatively charged

28. a) - Dry wood changes to black - bubbles of colourless gas b) Acidified K2Cr207 changes from orange to green Conc. H2S04 reduced to S02 which reduce acidified Cr202'7 to

chromium ions (Cr3+) which are green in colour

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Chemistry paper 1, 2&3 KERICHO SUB - COUNTY JOINT EVALUATION 233/2 JULY/ AUGUST 2016 CHEMISTRY PAPER 2 MARKING SCHEME

1. a) i) A and E or C and Dii) A, B and Ciii) Alkaline earth metals if A and E or

halogens if C and Db) Atomic radius of B is smaller than that of A. B has

stronger nuclear charge due to more protons hence pull the energy levels closer to the nucleus compared to A which has less protons

c) - making aircrafts parts since its light- making electrical cables since it is abetter conductor of electricity- extraction of metals like iron

d) D is more reactive than C, D has smaller atomic radius hence can attract the incoming electron more easily compared to C which has a larger atomic radius

e) AD2

f) ionic bondThere is complete transfer of electrons from E to oxygen

2. a) i) B - oxygen gas is liberated as a result of the discharge of OH" ion which are attracted by anode A hence B becomes the cathode

ii) Over wateriii) Anode40HT(aq) 2H20(i) + 02(g) + 4e-

CathodeCu2+(aq) + 2e- CU(S)

iv) Dissolving in nitric (V) acid and addingexcess aqueous ammonia to the solution.A deep blue solution of [Cu(NH3)4]2+ is formed

Q = It= 5 x 3 x 60 x 60=54000CCu2+ (aq) + 2e Cu(S)

2 x 9 6 5 0 0 = 193000C193000C 63.554000C ->?54000C x 63.5193000 = 17.77g

b) i) A - has the highest ability to lose electronsii) B(s) B2+(aq) // D2+(aq) / D(s)

iii) Ee = Ered - Eoxid.+0.34 - (-2.38)= +2.72 VOr

B(S) B2+ 2e- + .38

D2+ (aq) + 2e- D(S) + 0.34Ee = +2.38 + (+0.34)

= 2.72V3, a) i) I Polymerisation ½mark

II Fermentation ½markii) Step I

Reagent - hydrogen gas ½markCondition - nickel or platinum

Step IIReagent - concentrated sulphuric (VI) ac ½mark Condition - temp (160° - 180°) ½markStep VReagent-acidified potassium manganate (VII)Condition - heatb) i) Step VI

ii) Potassium propoxide ½markEthylpropanoate ½mark

c) - C3Hg decolourises acidified KMn04 while C3Hg

do not- C3H6 decolourises brown / yellow HOBr while

C3H8 do not- C3H6 burns with sooty flame C3Hg bums with

blue flame any two (2mks)d) i) [C3H6]n = 42000 ½mark

42n - 4200042 42

n = 1000ii) Non-biodegradable

4. a) i) Number of atoms of an element in onemoleculeii) Volume occupied by one mole of a gas at s.t.p or r.t.pb) i) When gases react, they do so in volumes which bear simple ratio to one another and to the volume of gaseous products provided all volumesare measured at standard temperature and pressure

ii) 2H2S(g) + 302(g) → 2S02(g) + 2H20(i)

2 vol 3 vol 2 vol

10cm3 40cmJ 10cm3

2vol → 10cm3

3 vol →x 10 = 15 cm3

Amount remaining 40-15 =25 cm3

Total volumes = 25 +10 102

Made up of 10cm3 of SO2 and 25 cm3 ofoxygen.

c) i) 1000 cm3 of Na2CO3→ 0.02 moles200cm3

==4.0 x 10-3 moles1 mole of Na2C03 10640 x 10-3 ?4.0 x 10-3x 106

1= 0.424g

Page | 213

Chemistry paper 1, 2&3 ii) CuO(s) + 2HCl(aq) CuCl2 + H20(i) iv) Yellow precipitate

1 : 2 v) Pb2+ (aq) + 21- (aq) Pbl2(s)Moles of CuO = 0.239 c) - making glass

79.5 - softening hard water= 3.006 x 10-3 mol - making sodium silicate used inMole ratio 1 : 2 detergents makingMoles of HC1 = 3.006 x 10-3 x 2 6. a) Heat= 6.0125 x 10-3 b) For condensed vapour not to flow back to the tube0.1moles of HC1 1000cm3 which might break it6.0125 x 1 0 - 3 ? c) Prevent mixing of air and hydrogen that causes6.0125 x 10-3 x 1000cm3 explosion

0.1 d) - black copper (II) oxide change to brown= 60.125cm3 - colourless liquid collects at the cooler parts

d) 23g Na contains 6.023 x 1023 atoms - white anhydrous CuS04 change to blue5.20 x 1023 atoms e) When hydrogen come in contact with air, it explode23g x 5.20 x 1023- atoms if ignited hence it is burned to avoid being release6.023 x 1023 to air= 19.8572g f) Prevent reoxidation of copper metal by air

5. a) - to HN03 add excess PbC03 as you stir until g) Yellow lead (II) oxide will change to orange theneffervescence stop grey

- filter the mixture and collect Pb(N03)2 as filtrate h) - bums with a blue flame- add soluble sulphate solution e.g. Na2S04 to - neutral to litmus paper

Pb(N03)2 to get PbS04(s) and NaN03(aq) 7. a) i) Bauxite- filter the mixture and collect PbS04 as residue ii) Silica or iron (III) oxide- rinse the residue and dry between filter paper b) i) On the diagramb) i) White precipitate soluble in excess ½ mark ii) I. It is expensive to maintain hence uneconomical

ii) White precipitate insoluble in excess½ mark II. Cryolite is addediii) White precipitate soluble on warming½ mark iii) Lower than operating temperature

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Chemistry paper 1, 2&3 KERICHO SUB - COUNTY JOINT EVALUATION 233/3 JULY/ AUGUST 2016 CHEMISTRY PAPER 3 MARKING SCHEME Table 1

Expt Vol. of A Vol of water Vo. of B Cone, of A Time 1/time

1 0.152 0.1253 0.14 0.0755 0.056 0.025

Complete table 2mksPenalise

- for unrealistic time (time 1 - should not be less than 10 sec. or more than 100 sec)

- for each empty space (to a maximum of 2mksTrends 1mk

- penalise Imk for time that is constant or decreasingDecimal place 1 mk

- accept 4d.p or !

Accuracy 1 mk+2 seconds to S.V

a) GraphScale mk- constant scale throughout both axes- plots cover at least Vi of graph on both axesLabelling mk

- both axes labelled and correct units shown plots 1 mk- Imk if at least five plots are correct- mk if at least four plots are correct Omk otherwise

Curve 1 mk- Imk if best line of fit drawn which must pass through the originb) i) - mk for showing on reading on graphs

- mk for correct reading of point shown (or not shown)correct working of reciprocal ii) yimk for evidence of reading

- '/2 for correct reading (whether shown or not) and correct working of reciprocalii) amk for evidence of reading and reading correctly

- mk for correct reading and correct working of reciprocalc) 1 mk

Rate of reaction is directly proportional to the concentration of reagents

Procedure IITable II 5mks distributed as follows :Complete table 1 mk

- if all spaces are filled- all arithmetic are correct- burette readings are realistic otherwise penalise to a max 1mk

Decimal place 1 mk- either if all readings are upto Id.p or if two readings are upto 2d.p with the second digit as 0 or 5

Accuracy 1mk- accept at least one titre within +0.1 of S.V for Imk

+ 0.2 of S.V for mkPrinciple of averaging

Page | 215

Chemistry paper 1, 2&3 - accept 2 or 3 consistent litres correctly chosen for ‘/-ink- accept correct average for correct titres for l/2mk

Final answer 1 mkfor correct average that favour the learner within +0.1 of S.V for Imk

+ 0.2 of SV tor Yzmk

ii) 2mks2M x Ans (i) x 25 = Ans (ii)

1000 250iii) l mk

25 x 0.2 = 0.005 1000

iv) 1 mkAns (ii): 0.005 = correct ratio

v) Imkoxidation state = +1Observations

Observations Inferences

- dissolve to form colourless solution - soluble salt- absence of Fe2+, Fe3+, Cu2+

a) No white precipitate Na+, K+, NH4+ present

Pb2+, Al3+, Zn , Mg2+ absent

b) Yellow flame Na+ present

c) White ppt that dissolve on adding HC1 - C02-3, S02-3 presenta) Decolourises KMn04 / turns acidified purple KMn04 colourless S02~3 present3. a) Observation Inferences- burns with a blue flame saturated organic compound

b) No effervesence -absence ofH+or R-COOHc) - decolourises purple acidified KMn04 R-OH, present

d) Yellow bromine does not decolourise R-OH present

Page | 216

Chemistry paper 1, 2&3 KEIYO SOUTH FORM FOUR JOINT EXAMINATIONS 2016 233/1 CHEMISTRY PRE - MOCK Paper 1 (THEORY) 2 hours

1. When Iron (III) chloride is exposed to the atmosphere, it forms a solution.(a) Name the process that takes place. (1 mark)(b) State one use of the process named in 1(a) above. (1 mark)

2. Study the energy level diagram for the reaction shown below and use it to answer the questions that follow.2SO2 (g) + O2 (g) →2SO3 (g)

(i) State and explain two ways of increasing the yield of SO3 per unit time from the diagram. (2 marks)(ii) What do the following represent?

H1 (½ mark)H2 (½ mark)

3. A student burnt magnesium ribbon in a gas jar full of sulphur (IV) oxide gas.i) State two observation made in the gas jar. (1 mark)ii) Write the equation for the reaction which took place (l mark)

4. The table below shows ammeter reading recorded when 2M Sulphuric (VI) acid and 2M ethanoic acid were tested separately.Electrolyte Current (A)2M Sulphuric acid 8.12M Ethanoic acid 2.5

Explain the difference in the ammeter readings. (2 marks)5. (a) Using electrons in the outermost energy level, draw a dot (.) and cross (X) diagram for the ion of PH4+ and compound

B2O3. (P=15, H=1, B=5, O= 16)(i) PH4+ (1 mark)(ii) B2O3 (1 mark)(b) The formula of the compound formed when Aluminum and chlorine react is Al2Cl6. Name the types of bonds that exist inthe compound. (1mark)

6. The graph below represents the solubility curve of a gas in water.

State and explain the conclusion that can be drawn from this curve about the solubility of the gas. (1 mark)

Page | 217

Chemistry paper 1, 2&3 (b) The solubility of salt T at 80oC is 40g / 100g of water. What mass of T will saturate 65g of water at 800C? (2mark)

7. State the conditions under which ammonia gives the following products when heated(i) Nitrogen and hydrogen. (1 mark)(ii) Nitrogen and water. (1 mark)(iii) Nitrogen (II) oxide and water. (1 mark)

8. Name the method of separation that can most suitably be used to separate the following mixturesa) Gasoline from petroleum. (1mark)b) Benzoic acid and potassium carbonate. (1mark)c) Oil from cashew nuts. (1mark)

9. The diagram below shows the set-up that can be used to prepare and collect oxygen gas. Study it and answer the questionsthat follow.

a) Identify two mistakes from the diagram which must be corrected for one to collect dry oxygen gas. (2marks)b) What property of oxygen gas makes it possible to be collected over water. (1mark)

10. The table below gives information about some reactions of metals A,B, C and D and their rates.

METAL Reaction with acid Reaction with water Action of heat on its nitrateA Hydrogen evolved No reaction Oxide formedB NO reaction No reaction Metal formedC Hydrogen evolved Hydrogen evolved Oxide formedD NO reaction NO reaction Oxide formed

Arrange the metals in order of decreasing activity. (2marks)11. The table below gives information on four elements by letters K, L, M and N. Study it and answer the questions that follow.

The letters do not represent the actual symbol of the elements.

Element Electron arrangement Atomic radius (nm) Ionic radius(nm)K 2.8.2 0.136 0.065L 2.8.7 0.099 0.181M 2.8.8.1 0.203 0.133N 2.8.8.2 0.174 0.099

a) Which two elements have similar properties? Explain. (2marks)b) What is the most likely formula of the oxide of L? (1mark)c) Which element is a non - metal? Explain. (1mark)

Page | 218

Chemistry paper 1, 2&3 12. Sulphur is extracted from underground deposits by a process in which three concentric pipes are sank down to the deposits as

shown below.

a) Name the process represented above. (1mark)b) What is passed down pipe J? (1mark)c) Name two allotropes of sulphur (1mark)

13. The set- up below was used to investigate the rate of diffusion of different gases.

a) Explain why a coloured liquid is used in this experiment. (1mark)b) State and explain the observation made after 20 minutes. (2marks)

14. 25.0cm3 of 0.12M potassium hydroxide solution required 30.0cm3 of a solution of a dibasic acid (H2R) for completeneutralization. The acid contained 3.15g per 500cm3 solution Calculate:a) The molarity of the acid solution. (1½marks)b) The relative formula mass of the acid. (1½ marks)

15. Methane gas reacts with chlorine gas as shown in the equation below.

u.vCH4(g) + Cl2(g) CH3Cl(g) + HCl(g)

lightUse the bond energies in the table below to calculate the enthalpy for the above reaction.(3marks)

Bond Bond energy kJ/ molC - H 413Cl - Cl 242C - Cl 346H - Cl 431

16. A student dissolved some ammonium nitrate salt in water in a glass beaker. The solution formed felt very cold. a) Explain why the temperature of the resultant solution dropped (1mark)b) Represent the above information on an energy level diagramb) What general name is given to such reactions (1 mark)

17. When a grey powder P, which has no action on cold water, is placed into a salt solution of Q, a brown solid R is deposited.The blue solution of Q, fades giving way to a green solution.a) Name the type of reaction that takes place. (1 mark)b) Identify solids P and R (1 marks)c) Write an equation for the reaction leading to formation of the brown solid. (1mark)

Page | 219

Chemistry paper 1, 2&3 18. The set-up below was used to investigate the effect of dry hydrogen gas on hot copper (ii) oxide powder.

Explain what is observed in the combustion tube during the experiment. 19. (a) Potassium manganate (VII) reacts with chloride salts to produce chlorine. Both chlorine and potassium manganate (VII)

are strong oxidizing agents. Which one of the two is the stronger oxidizing agent? Explain your answer (2marks)b) Chlorine and sulphur (IV) oxide are bleaching agents; explain the difference in their bleaching action. (1mark)

20. Calculate the number of molecules of water of crystallization in oxalic acid crystals, H2C2O4. xH2O, from the followingdata:5g of the crystals were made up to 250cm3 of this solution required 15.9cm3 of 0.5M sodium hydroxide to neutralize it.(H=1, C=12, 0 16, H20= 18) (3marks)

21. Two carbon electrodes were placed in a flask containing 50cm3 of 0.1 M barium hydroxide solution and connected in serieswith the 12 volt supply of direct current electricity and a lamp.1.0M sulphuric acid was slowly run into the solution from a burette until neutralization occurred.a) What would you see in the flask when the first few drops of acid are added? (1 mark)b) At the neutrality point, the lamp ceases to glow, explain why? (1 mark)c) What would you see if more 1.0 M sulphuric acid were now added? (1 mark)

22. Study the information in the diagram below and answer the questions that follow. (the letters do not represent the actualsymbols of the elements)

Element Electronic configuration Ionization energy KJ/MolP 2.1 519Q 2.8.1 494R 2.8.8.1 418

a) What is the general name given to the group in which elements P, Q and R belong? (1 mark)b) What is meant by ionization energy? (1 mark)c) Explain why element P has the highest ionization energy (1 mark)

23. Air is passed through several reagents as shown in the flow diagram below

Name one gas which escapes from chamber C. Give a reason for your answer (3marks)24. The diagram below shows the heating curve of a pure substance. Study it and answer the questions that follow.

Page | 220

Chemistry paper 1, 2&3 (a) What are the physical states of the substances at points W and Y. (1marks)(b) Explain why the temperature remains constant between points B and C. (2marks)

25. The equations show some reactions. Use the equations to answer the following questions.

CH3CH2OH Step I CH2=CH2 Step II CH3CH3

(a) Name the type of reaction in step I and II. (2marks)(b) Explain why ethene burns with a more smoky flame than ethane. (1mark)

26 (a) Graphite is a non- metal most commonly used as an electrode. State two properties that makes it suitable for use as anelectrode. (2marks)

(b) Graphite is an allotrope of carbon. Distinguish between allotropes and isotopes. (1marks)27. When solid Zinc carbonate was added to a solution of hydrogen chloride in methylbenzene, there was no observable change.

On addition of some water to the mixture there was effervescence. Explain these observations. (2marks)28. Study the chart below and answer the questions that follow.

(a) Name:(i) Cations present in mixture X. (1mark)(ii) Anions present in the solution. (1mark)(b) Write an equation to show how the white precipitate in step III is formed. (1mark)

Page | 221

Chemistry paper 1, 2&3 KEIYO SOUTH JOINT EXAMINATION 233/2 Chemistry Paper 2 PRE - MOCK 2 Hours

1. Study the set-up of apparatus below and answer the questions that follow.

L

Suction pump

a) State and explain the observation that would be made in tube L as the experiment progresses in the first few minutes.Observation. (1mark)Explanation. (1mark)

b) How would the observations in the tube L change if the experiment is carried out for a long time. Explain using a chemicalequation.Observation. (1mark)Equation. (1mark)

c) State three observations made when liquid S is reacted with sodium metal. (3marks)d) State the use of the suction pump in this experiment. (1mark)e) Diamond and graphite are allotropes of carbon. Graphite conducts electricity and diamond does not. Explain this

phenomenon. (2marks)f) State two uses of carbon (IV) oxide. (2marks)2. Study the information in the table below and answer the question that follow, letters do not represent actual symbols of the

element.

Element Atomic No. Melting point Boiling point Atomic radii Ionic RadiiL 3 -179 1340 0.108 0.100M 9 -220 -188 0.101 0.105N 11 98 890 0.135 0.132P 12 650 1110 0.126 0.124Q 13 660 2470 0.125 0.120R 15 442/590 280 0.111 0.119S 16 113/119 445 0.103 0.109T 17 -101 -3 0.109 0.120U 19 63.5 -775 0.167 0.160

a) Write the electronic configuration of an ion of elements T and U. (1marks)b) Why do the elements represented by R and S have two values of melting point. (1mark)c) Select an element:i) Which is the most electronegative. (1mark)ii) That belongs to period 4, explain. (2marks)d) Explain why:i) Ionic radius of R is bigger than its atomic radius. (1mark)ii) The atomic radius of L is bigger than that of R yet they are in the same period. (1mark)e) Using dots (.) and cross (x) to represent outermost electron show bonding in the compound formed between L and M.

(2marks)f) Write an equation for the reaction that occurs between U and water. (2marks)g) Describe how a solid mixture of the sulphate of element N and lead (II) sulphate can be separated into solid sample of dry

lead (II) sulphate. (2marks)3. The arrangements below shows a set-up to investigate the effect of an electric current on molten lead (II) iodide.

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Chemistry paper 1, 2&3

a) Identify two mistakes in the set-up. (2marks)b) State three observations made after correcting the mistakes. (2marks)c) What particles are responsible for electrical conductivity? (1mark)d) Write the equations for the reactions taking place at the electrodes.e) Indicate on the diagram direction of flow of electric current. (1mark)f) State two industrial applications of electrolysis process. (2marks)4. a) State Boyle’s law. (1mark)

b) The table below shows the relationship between the pressure and volume of a fixed mass of ozone gas.

Pressure (K pa) 1 4 8 16 20 160Volume (cm3) 140 40 20 10 8 1

Inverse of volume 1/v (cm-3)

(3marks)i) Complete the table by filling the inverse of volume.ii) Draw a graph of pressure against the reciprocal (inverse) of volume. (3marks)iii) Using the graph determine the volume of ozone if pressure is 12K pa. (2marks)

5. Equal masses of magnesium ribbon were reacted separately with equal volumes of 1M hydrochloric acid and 1M methanoic acid. The results were plotted on a graph as shown below. Two curves X and Y were obtained.

Volume of hydrogen (cm3).

Time in (sec).

a) Explain which curves represents: i) 1M hydrochloric acid. (1marks)ii) 1M Methanoic acid. (1marks)

b) State the significance of point Z. (1mark)c) On the same axes, sketch the curve you would obtain if the same mass of powdered magnesium were reacted with same

quantity of IM hydrochloric acid. Mark the curve w. (2marks)d) Write ionic equation for the reaction between magnesium and dilute hydrochloric acid. (1mark)e) Calculate the maximum mass of the gas that would be liberated if 1.2g of magnesium reacted with excess hydrochloric acid.

(Mg = 24, H =1).(2mks)f) Calculate the volume of the gas produced in (e) above at r.t.p (molar gas volume at r.t.p) = 24dm3. (3marks)

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Chemistry paper 1, 2&3 6. Study the structure below and answer questions that follow

a) What observation is made when the molecule above is heated to a temperature of 113 C (2marks)b) Write an equation for the reaction of atom of the above structure with hydrogen. (1mark)c) Study the scheme below and answer questions that follow.

L (aq) + M (g) + H2O

i) NameGas K (1mark)Gas M (1mark)

ii) State observation made inStep I (1mark)Step II (1mark)

iii) State the conditions necessary for step II to occur. (2marks)d) Write an equation to show how pollution effect of sulphur (IV) oxide is controlled in contact process. (2marks)e) Explain the role of sulphur in vulcanization of rubber. (2marks)7. a) Study the table below and answer the questions that follows

Formula of hydrocarbon Boiling points (K)C2H4 -104C3H6 -47.7C4H8 -62C5H10 30C6H12 63.9

i) What name is given to a series of organic compounds like the ones in the table? (1mark)ii) To what class of organic compounds does the above hydrocarbon belongs? (1mark)iii) Select one hydrocarbon that would be a gas at room temperature (298K) given a reason for your answer. (2marks) iv) Give the formula of the seventh member of the above series. (1mark)v) What is the relationship between the boiling point and the relative molecular masses of the hydrocarbons in the table above?

Explain your answer. (2marks)b. Study the flow chart below and answer the questions that follow

Alcohol X Ethene Compound Zconc. H2SO4 Heat HCl

Process Yi. Write the formula of Alcohol X, Compound Z and name process Y. (3marks)ii. Propane and Chlorine react as shown below :

CH3CH2CH3 CH3CH2CH2Cl+HCla) Name the type of reaction that takes place. (1mark)b) State the condition under which this reaction takes place. (1mark)

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Chemistry paper 1, 2&3 KEIYO SOUTH FORM FOUR JOINT EXAMINATIONS 2016 233/3 CHEMISTRY PRACTICALS CONFIDENTIAL PRE - MOCK In addition, to the common laboratory apparatus and fittings, each candidate should be provided with:

- About 80cm3 of solution R- About 100cm3 of solution Q- About 70cm3 of solution B- About 50cm3 of solution X- 1.06g of solid A accurately weighed- About 1g of solid E- 25ml pipette- 50ml burette- 250ml volumetric flask- 100ml plastic beaker- Three conical flask- Labels- 50ml measuring cylinder- Thermometer- Metallic spatula- Filter funnel- Filter paper- source of heat- boiling tube- six dry test tubes

Access to

- 2M sodium hydroxide solution- 2M aqueous ammonia- Acidified Barium nitrate solution- Barium nitrate solutiom- Lead (II) nitrate solution- Methyl orange indicator- Dilute nitric (V)acid- Sodium sulphate solution

NOTES- Solid E is mixture of calcium chloride and Lead(II) carbonate in the ratio of 1:1- Solution B is 1M nitric acid prepared by adding 64cm3 of concentrated acid to 700cm3 of water and making up to 1 litre.- Solution X is 1M sodium hydroxide solution prepared by adding 40g of sodium hydroxide pellets in 500cm3 of water and

making it up to 1 litre.- Solution R is 2M hydrochloric acid prepared by adding 172cm3 of concentrated acid in 600cm3 and making up to 1 litre.- Solution Q is 0.4M sodium hydroxide solution prepared by dissolving 16g of sodium hydroxide pellets in 200cm3 of water

and making it up to 1 litre.- Solid A is anhydrous sodium carbonate

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Chemistry paper 1, 2&3 KEIYO SOUTH FORM FOUR JOINT EXAMINATIONS 2016 233/3 CHEMISTRY PRACTICAL PRE - MOCK TIME: 2 ¼ HOURS

1. You are provided with:-2M Hydrochloric acid labeled as solution R -0.4M Sodium hydroxide solution labeled Q. -1.06g accurately weighed anhydrous carbonate X2CO3 labeled solid A You are required to determine atomic mass X in one mole of X2CO3 Procedure i) Using a clean measuring cylinder, measure 50cm3 of solution R and transfer in 100cm3 plastic beaker. ii) Add all solid A at once into the contents of the beaker, stir until effervescence stops. iii) Transfer this solution into a 250cm3 volumetric flask and add distilled water up to the mark. Label this solution as

solution S. iv) Fill the burette with solution Q v) Using a pipette and pipette filler, place 25cm3 of solution S into conical flask. Add 2 drops of methyl orange indicator. vi) Titrate solution S against solution Q. vii) Record your results in the table below. viii) Repeat the titration two more times and complete table I below. TABLE I

I II IIIFinal burette reading Initial burette reading Volume of solution Q used (cm3)

(4marks)

a) Calculate the;i) Average volume (1mark)ii) Number of moles of hydrochloric in 25cm3 of solution S (1mark)iii) Number of moles hydrochloric acid in 250cm3 of solution S, (1mark)iv) Number of moles of hydrochloric acid in 50cm3 of solution R (1mark)v) Number of moles of hydrochloric acid that reacted with 1.06g of A (1mark)vi) Number of moles of carbonate that reacted with solution R (1mark)vii) Relative atomic mass of X in one mole of X2CO3 (C=12,0=16) (1mark)

2. You are provided with- Solution B (1M HNO3)- Solution X (1M NaOH).

You are required to determine the heat of reaction per mole of B used using the procedure below Procedure i) Fill the burette with solution B ii) Using a measuring cylinder, put 20cm3 of solution X into a plastic beaker. Note its steady temperature. iii) Add 4cm3 of solution B from the burette and determine the highest temperature attained iv) Continue adding 4cm3 portions of solution B and every time determining the highest temperature attained v) Fill the highest temperature attained in table II below

TABLE II Volume of solution B (cm3) 0 4 8 12 16 20 24 28 32Temperature attained (0c)

(4marks)a) Plot a graph of temperature against volume of solution B. (3marks)b) i) From the graph determine the volume of solution B that reacts completely with 20cm3 of solution X (1mark)

ii) Determine the temperature change when solution X is completely reacted with solution B (1mark)c) Determine the heat evolved when the reaction is complete (2marks)

(Density of solution =1g/cm3, Specific heat capacity=4.2J/g/K)d) Determine the heat of reaction per mole of solution B used (2marks)e) Draw an energy level diagram for the reaction above. (2marks)3. You are provided with solid E. Carry out the following tests on E and record your observations and inference in the spaces

provided.(a) Place a spatula of solid E into a boiling tube and add 10cm3 of distilled water. Shake the mixture thoroughly. Filter the

mixture and divide the filtrate into four portions. Keep the residue for use in part (b).

Observation Inference(1mk) (½ mk)

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Chemistry paper 1, 2&3 ii) To portion one, add sodium Hydroxide solution drop wise until in excess.

Observation Inference(½ mk) (1mk)

iii) To portion two, add Ammonia solution drop wise until in excess.

Observation Inference(½ mk) (½ mk)

iv)To portion three, add four drops of Lead (II) Nitrate Solution.

Observation Inference(½ mk) 1mk

iv) To portion four, add four drops of Barium Nitrate solution

Observation Inference( ½ mk) (1mk)

b.i) Place a small amount of residue in metallic spatula and heat strongly in a non-luminous flame.

Observation Inference(1mk) (½ mk)

ii) Place the remaining solid in a boiling tube and add dilute nitric (v) acid little by little until all the solid dissolves. Divide thesolution into two parts.

Observation Inference(½ mk) (½ mk)

iii) To part one, add sodium Hydroxide solution drop wise until in excess.

Observation Inference(½ mk) (1mk)

iv) To part two, add Ammonia solution drop wise until in excess.

Observation Inference(½ mk) (1mk)

(iii) To portion three, add 3 drops of sodium sulphate solution.

Observation Inference(½ mk) (1mk)

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Chemistry paper 1, 2&3 KEIYO SOUTH FORM FOUR JOINT EXAMINATIONS 2016 233/1 CHEMISTRY Paper 1 (THEORY) PRE - MOCK MARKING SCHEME

1. (a) Deliquesence(b) Drying agent

2. (i) Reducing temperature favours exothermic reactionUsing Vanadium (V) Oxide as acatalyst lowers activation energy

(ii) H1…Activation energy (½ mk)

H2……Heat of reaction (½ mk)(b) Covalent and Dative bonds

3. i) Burning magnesium continues to burn.Yellow deposit of sulphur formed.

ii) 2Mg (s) + SO2 → 2MgO(s) + S(s)4. 2M Sulphuric (VI) Acid has a higher ammeter reading than 2 M ethanoic acid because its astronger acid and it ionizes in

water fully than ethanoic acid ionizes partially.5. (a) (i) PH4+

(ii) B2O3 (1 mk)

6. (a) Solubility is exothermic and it decreases with increase in temperature(b) ( )

7. (i) Temperature 5000c(ii) When burnt in an atmosphere enriched with oxygen (iii) Oxidation in the presence of platinum rhodium catalyst

8. a) Fractional distillation b) Sublimation c) Solvent Extraction

9. a) Delivery tube from the drying agent dipping in the drying agent. Collection by over water method isn’t appropriate since the gas is required dry.

b) Slightly soluble in water 10. Arrange the metals in order of decreasing activity.

CADB 11. a) KN. They belong to the same group

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Chemistry paper 1, 2&3b) OL2

c) L. Group 7 element. // ionic radius is greater than atomic radius. 12. a) Frasch process

b) Hot compressed air c) Rhombic (Alpha)

Monoclinic (Prismatic or Beta) 13. a) Better Visibility

b) Level of the liquid rises above level A and falls below level B. Hydrogen diffuses out of the porous pot faster than air diffuses into the pot. This leads to decrease in pressure inside the pot causing level at A to rise.

14. a) The molarity of the acid solution. (1½mks)( )( ) M

b) The relative formula mass of the acid.

15. u.vCH4(g) + Cl2(g) → CH3Cl(g) + HCl(g)

light

Bond Breaking Bond Formation3(C-H) =1239C-Cl = 346H-Cl =431

4(C-H)=413 4=1652Cl-Cl = 242 -2016

=+1894

Total = +1894-2016=-122kJmol-

16. a) Heat was absorbed from the surrounding b)

NH4NO3(aq)

Energy(kJmol-1) NH4NO3+(aq)

Reaction path

17. a) Displacement b) P-iron, R-copper c) Cu2+ (aq) +2e- →Cu(s)

18. Black copper (II) oxide changes brown, blue cobalt chloride paper changes pink

19 a) KMnO4 is a stronger oxidizing agent.it oxidizes chloride ion to chlorine b) Chlorine bleaches by oxidation, sulphur (IV) oxide bleaches by reduction

20.

( )( )90+18x=125.786

X=1.9881

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Chemistry paper 1, 2&3

21. a) White ppt b) All the barium ions that were conducting electricity were precipitated c) The lamp glows again

22. a) Alkali metal b) The energy required to remove an electron from an atom in a gaseous state. c) It has the smallest atomic radius / atomic size and therefore its valence electron experience greatest nuclear force of

attraction 23. Argon. Its inert 24. (a) W - Solid

Y-Liquid (b) The heat supplied is used to overcome intermolecular forces therefore causing the solid to melt.

25. (a) Step IDehydrationStep IIAdditional reaction

(b) Ethene has high Carbon Hydrogen ratio// Ethene is unsaturated26. (a) Good conductor of electricity

It’s inert and does not react with the electrolytes. (b) Isotopes are atoms of the same element having different mass number but same atomic number whereas/while allotropes are two or more different forms of an element in the same physical state.

27. In methylbenzene hydrogen chloride exists as covalent molecules while in water hydrogen chloride ionizes producing hydrogen ions which react with the carbonate producing carbon (IV) oxide.

28. (a) (i) Cu2+, Al3+

(ii) O2- , SO42-

(b) Al3+ (aq) + 3OH-(aq) → Al(OH)3(s)

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Chemistry paper 1, 2&3 KEIYO SOUTH JOINT EXAMINATION 233/2 Chemistry Paper 2 MARKING SCHEME PRE - MOCK 1a) a white precipitate is formed (1mk) CO2 reacts with Ca(OH)2(aq) to form insoluble CaCO3(s) (1mk) b) The white ppt dissolves to form a colourless solution (1mk) CaCO3(s) is converted to Ca(HCO3)2(aq)which is soluble CaCO3 (s) + CO2 (g) + H2O (l) Ca (HCO3)2 (aq) (1mk)c) Hissing sound.

Effevervesence/Bubbles of colourless gas are seen. (3mks) Sodium darts on S.

d) To suck gas produced.(1mk) e) In graphite 3 out of 4 electrons are used in bonding. One electron is delocalized hence it conducts electricity .(1mk) In diamond all the 4 electrons are used in bonding hence no delocalized electrons.(1mk) f) - Fire extinguishers.

- Refrigerant. (2mks)- Fizzy drinks.

2a)T- 2.8.7(1mk) U-2.8.8.1(1mk)

b) because of the presence of allotropes(1mk) c) i) T-(1mk)

ii) U - (1mk)Explanation because it has four energy levels.(1mk)

d) R form ions by gaining electrons. The incoming electrons cause electron repulsion that makes the energy level to bulge out increasing the size (1mk) ii) The nuclear charge increases from L to R hence an increase in nuclear attraction which pulls the energy levels to the nucleus. (1mk)

e) L - 2.1M - 2.7

f) U-19-2.8.8.12U (s) + 2H2O (l) → 2UOH (aq) + H2 (g) (2mks)

g) Add water ½ to the mixture.Filter ½ the mixture to remove PbSO4 as residue. Wash ½ the residue with distilled water. Dry ½ between two filter papers. (2mks)

3.a) Used a beaker in strong heating.(1mk) No heat.(1mk)

b) Bulb lights. (1mk) Cathode - purple vapor.(1mk) Anode - Grey beads.(1mk)

c) Ions.(1mk) d) Cathode 2I- (l) → I 2 (g) + 2 e-(1mk)

Anode Pb 2+ (l) + 2 e- → Pb(s)(1mk)e) from the positive terminal to the negative terminal of the battery(arrow on the wire). f) -Extraction of reactive metals or extraction of metals e.g. Na, Al, Mg.

-Electroplating. -Purifying metals. -Manufacture of NaOH and chlorine. (any two 2mks)

3 a) The volume of a fixed mass of a gas is inversely proportional to its pressure at constant temperature. (1mk)b) (i)

Pressure 1 4 8 16 20 160Volume 140 40 20 10 8 11/v 0.006 0.025 0.05 0.1 0.125 1.000

(3mks) ii)axes-1/2mk,scale-1/2mk,line-1mk,plotting-1mk iii) Reading from the graph (student graph)(1mk) -evaluation on the reciprocal of volume.(1mk)

5a) X - Hydrochloric Acid X is a strong Acid(1mk)

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Chemistry paper 1, 2&3 Y - Methanoic Acid is a weak acid.(1mk) b) End of the reaction.(1mk) c) a curve above X on the graph marked W and end point at Z.(2mks) d) Mg (s) + 2H+ (aq) Mg 2+ (aq) + H2 (g)(1mk)e) Mole ratio 1:1

Moles of Mg (s) = 1.2 = 0.05 moles 24

Mole of H2 = 0.05 molesMass of H2 = 0.05 x 1

= 0.05g(2mks)f) moles of H2 = 0.05

volume of H2 = 0.05 x 24= 1.2 litres or 1200 cm3(3mks)

6. a) Yellow solid melts into amber liquid.(2mks)b) H2 (g) + S (s) →H2S (g) (1mk) Penalise ½ for wrong state symbol / penalize fully for unbalanced eqn.c) (i) K - Hydrogen sulphide 1 reject H2S(1mk)

M - sulphur (IV) oxide 1 reject SO2(1mk) ii) Step I -Blue flames ½ misty fumes ½ chocking smell.(1mk)

Step II-a vigorous reaction that produces white fumes.(1mk) iii)-Temp of 450oC. (1mk)

-Pressure of 2 to 3 atmosphere.(½mk) -V 2 O5 finely divided platinum or silica(½mk)

d) Ca(OH)2 (aq) + SO2 (g) → CaSO3 (s) + H20(l) (2mks)e) It makes the rubber tougher, less flexible, and less soft by reducing number of double bonds.(2mks) 7(a) (i) alkenes.(1mk) (ii) Unsaturated hydrocarbons.(1mk) (iii)C2H4/C3H6/C4H8, its boiling point is below room temperature.(2mks) (iv) C8H16(1mk) (V)Boiling point increases with increase in relative molecular mass, due to increase in intermolecular forces.(1mk) (b)(i) X- C2H5OH.(1mk)

Y-dehydration.(1mk) Z-C2H5C.l(1mk)

(ii) (a) substitution reaction.(1mk) (b) Presence of sunlight/UV light.(1mk)

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Chemistry paper 1, 2&3 KEIYO SOUTH JOINT MOCK 233/3 CHEMISTRY PRACTICAL PRE - MOCK MARKING SCHEME

1. TABLE Ia) Complete table 1mk

Conditions- Complete table with 3 titrations 1mk- 2 titrations ½ mk- 1 titration 0mk

Penalties- wrong arithmetic- Inverted table- Unrealistic values

Penalize to a max of 1mkb) Use of decimals 1mk- 1 or 2 decimals used consistently- If 2 decimals the second decimal must be 0 or 5

Penalize fully if any of the conditions is not metc) Accuracy 1mk- Compare candidate’s reading with S.V/C.V

Conditions- If at least one of the values is within 0.1 of S.V 1mk- If any of the values is within 0.2 of S.V ½ mk- If none is within 0.2 of S.V 0mkd) Principles of averaging 1mk- Values averaged must be consistent within 0.2

Conditions- if 3 values averaged 1mk- if 3 titrations done, only 2 possible averaged 1mk- if 2 or 3 inconsistent values averagrd 0mk

CALCULATIONSa) (ii) moles of Q=(0.4X Av volume)/1000 ½ mk

Moles of S= no of moles of Q in average volume(use of reacting mole ratio should be shown) ½ mk(iii) answer in (ii) X 10(iv) (50X2)/1000

=0.1(v) 0.1 - answer in (iii)(vi) moles in (v) x2(vii) 1.06/answer in (vi)

2. TABLE IIComplete table 2mksConsistent use of decimals ½ mkAccuracy ½ mkTrend 1mk(a)GRAPH

- Plotting 1mk- Scale ½ mk- Axes ½ mk- Line 1mk(b) (i) volume read from extrapolated graph 1mk

(ii) temperature change = highest temp as read from graph-lowest temperature

(c) heat = mass of sol x specific heat capacity x temp. change mass of solution=[20+ volume in (b, i)]X 1g/cm3(d) [answer in c x 1]/moles of B used(e) energy level diagram for exothermic reaction3. (a) (i)

Observations Inferences- White residue - Solid is a mixture of soluble and insoluble salts- Colourless filtrate - Absence of Fe2+, Fe3+ or Cu2+

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Chemistry paper 1, 2&3

(ii) Observations Inferences- White ppt insoluble in excess - Ca2+, Mg2+ or Ba2+

Observations Inferences- No White ppt - Ca2+

Observations Inferences- White ppt - SO42-, SO32- , CO32-, Cl-

Observations Inferences- NO White ppt - Cl-

(b) (i)

Observations Inferences- Red/brown residue when hot and - PbO present

yellow when cold(b) (ii)

Observations Inferences- effervescence - CO32-

(b) (iii)Observations Inferences- White ppt soluble in excess - Al3+, Pb2+, Zn 2+

(iv)Observations InferencesWhite ppt insoluble in excess - Al3+ or Pb2+

(v)

Observations Inferences- White ppt - Pb2+

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Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION

233/1 CHEMISTRY PAPER 1 (THEORY) 2016 TIME: 2 HOURS

1. (a) The diagram below shows a non-luminous flame. Use it to answer the questions that follow:

Two wooden splints were placed across regions X and Y respectively. Draw labelled diagrams to show the effects observed on the wooden splint placed across each region. (2 marks)

(i) Region X.(ii) Region Y.(b) It is advisable to leave your flame in the luminous state when not in use. Give a reason why. (1mark)2. Explain the change in mass expected when each of the following substances is heated in an open crucible.

(a) Copper metal. (1 mark)(b) Copper (II) nitrate. (2 marks)

3. The table below shows PH values of solutions A, B, C and D.Solution PH

A 3.0B 13.0C 8.5D 7.0

(a) Identify a solution which is(i) Strongly acidic. (½ mark)(ii) Strongly basic (½ mark)

(b) Which to solutions would react with lead (II) oxide? Explain. (2 marks)4. In an experiment a certain volume of air was repeatedly passed between two syringes over heated zinc powder as shown

below.

The same experiment was repeated using magnesium turnings instead of zinc powder. In which of the two experiments wasthe overall change in volume greater? Explain. (3 marks)

5. The grid below is part of the periodic table. Study it and answer the questions that follow. The letters are not actual symbolsof elements.

A D E H IB C M F G J

(a) What is the name given to the chemical family of element C? (1 mark)(b) Would element B react with J? Explain. (1 mark(c) Compare the melting points of B and M. (1 mark)

6. The atomic numbers of nitrogen, oxygen and sodium are 7, 8 and 11 respectively.(a) Write the electron arrangements of their ions, N3-, O2- and Na+. (1 mark)(b) Arrange the 3 ions in increasing order of size. Give a reason for your answer. (2 marks)

7. The melting point of phosphorous (III) chloride is -91C while that of magnesium chloride is +715C. In terms of structureand bonding explain the difference. (3 marks)

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Chemistry paper 1, 2&3 8. The diagram below illustrates how magnesium would react with steam. Study it then answer the questions that follow.

(a) Write the equation for the reaction that takes place. (1 mark)(b) Explain why this experiment cannot be carried out with potassium in the same way as shown. (1 mark)

9. Explain why graphite is used as a lubricant in moving machine parts where a lot of heat is produced. (2 mark)10. Calculate the volume of carbon (IV) oxide that would be produced if 15g of calcium carbonate reacted with 100cm³ of 2.0M

hydrochloric acid (C = 12.0, O = 16.0, Ca = 40.0) molar gas volume = 24000cm³. (3 mark)11. (a) Study the diagram below hence answer the questions that follow.

(i) Explain why it is necessary to have the flame at M. (1 mark)(ii) Write down the equation for the reaction inside the combustion tube. (1 mark)(c) Explain potassium hydroxide is not a suitable reagent for testing carbon (IV) oxide. (1 mark)

12. The table below contains information regarding a species of helium.Species Number of electrons Number of neutrons3

2

2 HeComplete the table by indicating the numbers of electrons and neutrons. (2 marks)

13. (a) The diagram below represents a set-up of apparatus used to investigate the effect of electric current on lead (II) bromide.

Describe what is observed at electrode C. (1 mark)(b) A current of 2.5A was passed through a cell containing N2+ ions for 25 minutes. The mass of the cathode increased by 0.36g.

Determine the R.A.M of N. (F = 9.65 x 104Cmolˉ¹). (2 marks)14. When aluminium chloride is dissolved in water, the resulting solution has a PH of 3. Explain. (3 marks)15. Study the scheme below hence answer the questions that follow.

Solid Q + Ca(OH)2

Step I

Ammonia

Pass into aluminiumsulphate then filter Step II

Solid P

(a) Identify solid Q.__________________________________________________ (1 mark)(b) Write an ionic equation for the reaction in Step II. (1 mark)

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Chemistry paper 1, 2&3 (c) State the condition necessary for Step I. (1 mark)

16. When sulphur is heated in a boiling tube in the absence of air, the yellow crystals melt into a golden yellow mobile liquid at 113C. The liquid turns into a dark brown viscous mass at 180C. At 400C the brown liquid becomes less viscous and flows easily. Explain these observations. (3 marks)

17. Study the diagrams below.

(a) State the observations made at I and II (b) Write the equation to show the reactions at II if dry sulphur (IV) oxide was used in place of dry chlorine.

(2 marks) 18. In an experiment soap solution was used against 3 separate samples of water. Each sample was later boiled and soap added.

Each water sample was 1000cm³. The results are tabulated below.

Volume of soap used to form lather SampleI II III

Before boiling (cm³) 27 3 10.6After boiling (cm³) 27 3 3

(a) Which sample was likely to be soft water? Explain. (2 marks)(b) State the cause of change in volume of soap used to form lather in sample III. (1 mark)

19. Study the cycle below hence answer the questions that follow.

Fe(S) FeCl2

H3 H2Fe Cl3

(a) What is H3? (1 mark)(b) Show the relationship connecting H1, H2 and H3 (1 mark)

20. When bromine gas reacts with aqueous sodium hydroxide an equilibrium is established as shown below.Br2(aq) + 2 OH(Brown)

aq

Br + OBr + H2O(l) aq aq

(Colourless) What observation would be made if a few drops of dilute sulphuric (VI) were added to the equilibrium mixture? Explain.

(2 marks) 21. (a) Aqueous sodium sulphate was electrolysed using platinum. Name the products at each electrode.

(1 mark)I Cathode_______________________________________________________________II Anode________________________________________________________________

(b) Explain why it is not advisable to use potassium chloride as salt bridge in the cell shown below.2 2

Pb(S) / Pb aq // Cu aq / Cu(S) E = +0.47V (1 mark) 22. A compound has empirical formula C3H6O and relative formula mass of 116. Determine it’s molecular formula.

(C = 12, H = 1, O = 16). (2 marks)23. (a) State the law of combining volumes of gases. (1 mark)

(b) What volume of methane would remain if a burner containing 40cm³ of methane burns in 40cm³ of enclosed air(assuming that oxygen is 20% of air)? (2 marks)

24. The molecular formula of compound T is C3H8O. T reacts with acidified potassium manganate (VII) to form anothercompound U whose formula C3H6O2. T also reacts with sodium metal to produce hydrogen gas and T is neutral to litmus.(a) Suggest the homologous series to which T belongs. (1 mark)(b) Name the type of reaction leading to the formation of U in the reaction described above. (1 mark)(c) Write the structural formula of U. (1 mark)

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Chemistry paper 1, 2&3

25. Potassium has two isotopes 39

19

40K and radioactive K

19 (a) State how the two isotopes differ. (1 mark)(b) The half-life of 40

19

K is 1.3 x 109 years. Determine how long it would take for 4g of the isotope to decay to 1g.

(1 mark)

(c) 39

19K undergoes beta decay to form an isotope of calcium. Write the equation for this decay. (1 mark)

26. The diagram below represents a section of the hydrochloric acid manufacturing plant.

(a) Name Y.________________________________________________________(b) State the role played by glass beads.(c) Chlorine reacts with hydrogen sulphide gas according the equation shown below:

H2S(g) + Cl2(g) 2HCl(g) + S(S)

From the equation identify the oxidizing agent.27. The formulae below belong to 2 cleansing agents.

I RCOO- K+

(1 mark)(1 mark)

(1 mark)

II R OSO 3K(a) Which of the two cleaning agents would lather readily with hard water? (1 mark)(b) State one disadvantage of the continued use of cleansing agent II. (1 mark)(d) Write the formula of the compound formed when cleansing agent I is used with water containing Mg2+ ions.

(1 mark) 28. Starting with solid lead (II) carbonate, briefly describe how a sample of lead (II) chloride can be prepared.

(3 marks) 29. (a) State Boyle’s law. (1 mark

(b) 60cm³ of oxygen gas diffused through a porous hole in 50 seconds. How long will it take 80cm³ of sulphur (IV)oxide to diffuse through the same hole under the same conditions(S = 32, O = 16). (2 marks)

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Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION 233/2 CHEMISTRY Paper 2 (THEORY) 2016 TIME 2 HOURS

1. The table below shows elements, atomic numbers and their melting points. The letters do not represent actual symbols of theelements. Study it and answer the questions.

Elements Atomic numbers Melting pointJ 11 98ocK 16 115oc (119oc)L 15 44ocM 14 1410ocN 12 650oc

(a) Write the formula of the oxide of M (1 mark)(b) Choose an element that would give a basic oxide when burned in air. Give a reason. (2 marks)(c) Element K has two melting points. Explain why? (2 marks)

(d) The melting point of element M is 1410oc. What is the possible structure of element M. (1 mark)(e) Compare the reactions of J and water to that of N and water (2 marks)(f) Choose an element that would form only covalent compounds. Explain (2 marks)(g) Write an equation for reaction of L and oxygen (1 mark)2. An aqueous solution of zinc sulphate is electrolysed using platinum electrodes as shown below in the set up.

a) (i) Write down the ionic equation for the reaction taking place at electrode producing gas X(1 mark)(ii) Identify the gas produced at Y; give a reason (2 marks)

b) 0.22 g of metal g is deposited by electrolysis when a current of 0.06 amperes flows for 99 minutes. (G=184, IF = 96500C)(i) Find the number of moles of metal deposited (1mark)(ii) Find the number of moles of electrons passed (3 marks)(iii) Determine the value of n in the metallic ion Gn+ (2 marks)

c) The following are half-cell reactions and their reduction potentials

Eθ (volts)A2+ + 2 e A(s) -0.76B2+(aq) + 2 e B(s) -0.13C(aq) + e C(s) +0.80D2+(aq) + 2 e D(s) +0.30

(i) Write the cell representation for the electrochemical cell that would give the highest Eθ value. (2 marks)(ii) Give one industrial use of electrolysis (1 mark)

3. (a) State Hess’s law (1mark)

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Chemistry paper 1, 2&3 (b) Using the following thermochemical equations draw an energy cycle diagram. (3 marks)

A. 2C(s) + H2(g) C2H2(g) ∆H = + 227 Kj/molB. C(s) + 02(g) CO2(g) ∆H = -394 Kj/molC H2(g) + ½ O2(g) H20(g) ∆H = -286 Kj/mol

(c) Name the heat of change represented by thermochemical equation A (2 marks)(d) Using thermochemical equationsA, B, C. Calculate the molar heat of combustion of ethyne (3 marks)(e) Give 3 factors considered for choosing a good fuel (3 marks)

4. Biogas is made from natural organic waste. A from four student set -up the apparatus below to investigate the compositionof the gas. He passed it over heated copper (II) oxide. After that he obtained two products. One was cooled in a boiling tubewhile the other was collected using a syringe.

(a) What is the function of calcium oxide (1 mark)(b) Name producti) Pii) Y (2marks)

(c) Give the two observations made in tube X (2 marks(d) i) Name the type of reaction taking place in tube X (1 mark)

ii) Write the equation for the reaction above in (d)(i) (1 mark)(e) What elements are present in biogas (2 marks)(f) Explain why one tube in boiling tube Q is longer than the other (2 marks)5. Below is a simplified diagram of the Downs cell used for the manufacture of sodium.

study it and answer the questions that follow:

P

(i) Explain why the anode is not made of steel. (2 marks)(i) What precaution is taken to prevent chlorine and sodium from recombining? (1 mark)(ii) Write an ionic equation for the reaction that took place at the : (2marks)

(I) Anode. (II) cathode

(b) (i) In the Downs process calcium chloride salt is added to sodium Chloride. Explain why? (2 marks(ii) In Down’s process liquid calcium metal may also be formed alongside liquid sodium metal. Explain how the two can beseparated. (1 mark)

(c) Explain why aqueous sodium chloride is not suitable as an electrolyte for the manufacture of sodium in the Downs process.(2 marks)

(b) Sodium reacts with water to form sodium hydroxide and hydrogen gas.(i) Write the equation for the reaction. (1 mark)(ii) Explain two observations made on placing a piece of sodium metal in water (2marks)(I) Sodium melts into a silvery ball.(II) Solution turns methyl orange yellow.6. (a) Production of Nitrogen(II) oxide follows the equation below represented by the equation

N2(g) + O2(g)2NO(g) ∆H= +180 kJ /mol.

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Chemistry paper 1, 2&3 (h) What is meant by the word equilibrium (2 mark)(b) With reasons explain what would happen when(i) Pressure is increased in the system in (a) above (2 marks)(ii) Temperature is increased (2 marks)(iii) Nitrogen (II) Oxide is removed (2 marks)(c) An equilibrium exists between

2NO2(g) N2O4(g)

On the grid below sketch how the concentration of NO2 varies with the reaction path (3 marks)

Concentration of NO3

Reaction path

7. (a) State how burning can be used to distinguish between prepane and propyne. Explain your answer. (3marks) (b) Draw the structural formular of the 4th member of the homologous series in which propyne is a member

(1mark) (c) The flow chart below shows a series of reactions starting withpropan-l-ol. Study it and answer the questions that

follow.

NaOHPropanoic acid

Process Y

Propan -l-ol

ConcentratedH2SO4 Process W

Gas R

High Pressure

Polymer X

(i) Name:

C

Sodalime Heat

Ethane

I. Process Y……………………………………………………….. (1mark)II. Substances R and CIII. Process W……………………………………………… (1mark)IV. Polymer X……………………………………………… (1mark)

(ii) Write a balanced chemical equation for the combustion of propane. (1mark)(iii) State oneuse of polymer X (1mark)

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Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION 233/3 CHEMISTRY FORM FOUR PRACTICAL Paper 3 TIME: 2¼ HOURS

1. You are provided with 10g of solid A which is a mixture of sodium carbonate and sodium chloride. 0.2 M HCl solution B

You are required to

Determine the concentration of sodium carbonate in the mixture. Percentage of sodium chloride in the mixture.

Procedure Transfer the entire solid into a 250 Ml volumetric flask. Add about 100cm3 of distilled water. Shake to dissolve. Top up with more distilled water to make up to the mark. Label this solution A2. Using a pipette and a pipette filler, transfer 25 cm3 of this solution into a conical flask. Repeat the procedure two more times to complete table 1

Table 1 I II III

final burette reading (cm3)initial burette reading(cm3)volume of solution B used (cm)3

(a) Calculate(i) The average volume of solution B used ( 1mark)(ii) The number of moles of HCl in the average titre (1 mark)(b) Write an equation for the reaction ( 1mark)(c) calculate the number of(i) Moles of sodium carbonate in 25cm3 of solution A2 (1 mark)(ii) The moles of sodium carbonate in 250 cm3 of solution A2 ( 1 mark)(d) Determine the mass of sodium carbonate in solid A (1 mark)

(Na=23, C = 12.0, H=1.0 , O= 16)

(e) Calculate the percentage of sodium chloride in solid A ( 1 mark)2. You are provided with Solution D, 2MHCl Solution C 2 M NaOH

You are required to determine the heat of neutralization

Procedure Wrap a plastic beaker with tissue paper and secure it with a rubber band. Use a measuring cylinder to transfer 20cm3 of solution C into a plastic beaker. Take its initial temperature and record it in table 2 below. Using a clean measuring cylinder, measure 5 cm3 of solution B and add it to solution C. Stir the mixture immediately with a thermometer and record the highest temperature in table 2 Continue adding 5 cm3 portions of solution every time record the highest temperature attained to complete the table Table 2

Volume of D add cm3 0 5 10 15 20 25 30Volume of A+D cm3 20 25 30 35 40 45 50Temperature of mixture oC

(4 marks)Plot a graph of volume of solution D (X-axis) against highest temperature (3 marks)

(a) From the graph:(i) Determine the volume of solution D that reacts completely with solution C. (1mark)(ii) The highest temperature change∆ T (1 mark(b) (i) Calculate the amount of heat evolved by the reaction (assume specific heat of capacity =

4.2Jg -1 K-1, density of solution = 1 g/cm3) (1 mark)(ii) Calculate the number of moles of HCl used (1 mark)(iii) Calculate the molar heat of neutralization of HCl (2 marks)

Page | 242

Chemistry paper 1, 2&3 3. (a) You are provided with solid E. Carry out the following tests and write your observations and inferences in the spaces

provided.(i) Place one third of solid E on a metallic spatula and ignite using a Bunsen burner flame

observation Inferences

( 1 mark) ( 1 mark)

(ii) Place all the remaining solid in a boiling tube. Add 5cm3 of distilled water. Shake to dissolve and divide it into 4portions

(I) to the first portion add three drops of acidified potassium manganate (VII)

observation Inferences

( 1 mark) ( 1 mark)

(II) To the second add three drops bromine water.

observation Inferences

( 1 mark) ( 1 mark)

(III) To the third portion add all the sodium hydrogen carbonate provided

observation Inferences

( 1 mark) ( 1 mark)

(b) You are provided with solid F. Carry out the tests below and record your observations and inferences in the spaces provided.Place all the solid F in a boiling tube. Add 10cm3 of distilled water. Divide into four portions.

observation Inferences

( 1 mark) ( 1 mark)

(i) To the first portion, add aqueous hydroxide drop wise until in excess.

observation Inferences

( 1 mark) ( 1 mark)

(ii) To the second portion add 5 drops of barium nitrate solution, followed by 3 drops of dilute nitric acid.

observation Inferences

( 1 mark) ( 1 mark)

(iii) To the third portion add 3 drops of acidified sodium dichromate (VI) solution

observation Inferences

( 1 mark) ( 1 mark)

Page | 243

Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION 233/1 CHEMISTRY PAPER 1 MARKING SCHEME 2016

1. (a) (i)

(ii)(b) For easier visibility. ¹

2. (a) Mass increases as oxygen combines with copper ¹(b) Mass decreases as ¹ gases escape during decomposition ¹

3. (a) (i) A ½(ii) B ½

(b) A and B¹Lead (II) oxide is amphoteric ¹

4. - Experiment with magnesium ¹- Zinc reacts with oxygen only while ¹- Magnesium reacts with both oxygen and nitrogen. ¹

5. (a) Alkaline earth metals. ¹(b) J does not form compounds as it is chemically stable already. ¹(c) M has a higher melting point than B as it has a stronger metallic bond. ¹

6. (a) 2.8 ¹(b) Na+, O2-, N3-¹

No of protons decrease to the right hence reducing the effective nuclear charge. ¹7. - PCl3 has a simple molecular structure with ½

- Weak van der waals inter-molecular forces ¹- MgCl2 has a giant ionic structure with ½- Strong electrostatic forces between the oppositely-charged ions. ¹

8. (a) Mg(S) + H2O(g) MgO(S) + H2(g) ¹(b) Potassium would react explosively with steam. ¹

9. Graphite has a giant atomic structure hence. ¹high boiling point and is more stable than oil. ¹

10. CaCO3 + 2HCl CaCl2 + H2O + CO2¹Moles of CaCO2 = 15 ½

100Moles of HCl = 2

0 15½

1000 100 0 2

Moles of CO2 produced 0 22

0 1 ¹

Volume of CO2 produced = 0.1 x 24000 ½= 2400cm³½

11. (a) (i) To burn off carbon (II) oxide which is highly poisonous. ¹(ii) H2O(g) + C(S) CO(g) + H2(g) ¹

(b) Potassium hydroxide forms soluble carbonate and hydrogen carbonate. ¹12. Electrons neutrons

O ¹ 1 ¹13. (a) Grey solid ½, Pb2+ ions are discharged as Pb(S) ½

(b) Q = 2.5 x 25 x 60 = 3750C ¹0 36 193000

M 3750 18 5 ¹

14.

15.

Aluminium chloride is hydrolysed ¹ by water to produce H+ ions ¹to produce HCl, a strong acid ¹(a) Ammonium chloride. ¹

3 (b) Alaq 3OH aq AlOH 3 (S)¹(c) Heat ¹

16. - Mobile liquid comprises of S8 molecules ¹- Dark viscous liquid as the S8 chains entangle ¹- The S8 molecules fold into rings which flow independently. ¹

17. (a) - No bleaching. ½- Bleaching ½

Page | 244

Chemistry paper 1, 2&3

(b) SO2(g) + H2O(l) 2

2 2 H aq SO 3 aq ¹2

SO3 aq Dye SO4aq Bleach ¹18. (a) Sample II ¹

- Requires little soap to lather ¹(b) Temporary hardness removed after boiling. ¹

19. (a) Heat of formation of FeCl3 ¹(b) H3 = H1 + H2 ¹

20. Brown colour would intensify.¹OH- Removed by addition hence ½ backward reaction triggered to replace OH-½

21. (a) I Hydrogen ½II Oxygen ½

(b) Precipitation of PbCl2 prevents flow ¹22. 58n = 116 ½

n = 2 ½ C6H12O2¹

23. (a) When gases react, they do so in simple ratios of volumes and those of their products if gaseous.¹(b) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ½

20 3

100 40 8 cm of O2 ½

Volume of CH 4 82

3 4 cm½

Volume remaining = 40 - 4 = 36cm³ ½24. (a) Alkanols ¹

(b) Oxidation ¹(c) H H

H C C C O H

H H O

40 3925. (a)

19 K has 21 neutrons while K has 20 ¹19

(b) 4 h 2 h 1 2h2 x 1.3 x 109 = 2.6 x 109¹40 40 o

(c) 19 K Ca 1 20

26. (a) Chlorine ¹(b) Increases surface area for dissolving process ¹(c) Cl2¹

27. (a) II(b) Non-biodegradable hence leads to water pollution. ¹(c) (RCOO-)2Mg2+¹

28. - To excess lead (II) carbonate, add nitric (V) acid ¹- Filter to obtain lead (II) nitrate filtrate. ½- Add dil HCl acid. ¹- Filter to obtain lead (II) chloride residue. ½

29. (a) The volume of a fixed mass of a gas is inversely proportional to itspressure at constant temperature. ¹

(b) 60cm³ - 50sec.80cm³ ? 80 50 ¹

t At B

t B

60

M AM B

66 67 64 ¹32

66 67 sec

= 94.28sec ¹

Page | 245

Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION 233/2 CHEMISTRY PAPER 2 MARKING SCHEME 2016 1. (a) M O2

(b) J and N; Oxides of metals (c) K - has two allotropes (d) giant atomic structure (e) J reacts vigorously while that of N is rapid (f) M, electronic configuration - 2,8,4 cannot lose 4 or gain electrons that is shares (g) 4 L (s) + 5 O2 → 2 L2 O5(s) / 4 P + 5O2 → 2 P2O5

2. (i) 4 O H-(aq) → O2(g) + 2H2O(l) + 4 e(ii) Hydrogen; volume is twice that at X.(b)(i) 0.22 = 0.0012

184(ii) Q = 0.06 x 99 x 60

= 356.4 C.0.22 → 356.4184 → 356.4 x 184

0.22= 65577.6 C.

96500C → IF65577.6C → 1 x 65577.6

96500= 3 F.3 moles of electrons.

(iii) Gn+ = +3(c)(i) A(s) /A2+(aq) // C+(aq) / C(s)

(ii) Electroplating3. (a) the heat change in converting reactants to product is regardless of the

route followed.(b) 2C(s) + H2(g) → C2H2(g)

+O2 +1/2 O2 + 3 /2 O2

CO2(g) + H2O(g)

(c) Heat of formation of ethyne (d) +227 = 2 x -394 + -286 - ∆Hc

∆Hccomb = 2 x - 394 -286 -227 = - 1301 kJ/mol.

(e) - Availability- Cheap - Environmental friendly - High energy

4. (a) to dry the biogas(b) P - water

Y - CO2

(c) - black substance turns brown- colourless liquid formed on cooler parts of tube X

(d) (i) Reduction(ii) 4Cu O(s) + CH4(g) → 4Cu(s) +CO2(g) + 2H2O(l)

(e) Carbon, Hydrogen (f) - to allow product P to condense

- Also for product Y to be collected by syringe.5. a) (i) Chlorine gas reacts with steel hence corroding it.

(i) use of steel diaphragm prevents to prevent the mixing of the two.(ii) i) anode - 2CL⁻(l) → Cl2(g) + 2e⁻

ii) Cathode - Na+(l) + e⁻+ Hg(s) → Hg/Na(l)

Page | 246

Chemistry paper 1, 2&3 b) (i) to lower m.p of NaCl thus reducing the cost of production. (ii) fractional distillation of liquidified metal c) H+ ions are lower than Na+ ions in the electro chemical series Hence H+ ions would be discharged instead of N. b) (i) 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

(ii) i) sodium is less dense than water ii) sodium hydroxide solution formed is alkaline.

(i) Equilibrium is the state of balance where the rate of forward and rate of backward reaction is the same. (b) (i) No change, reactant and product side have equal volume 2,2.

(ii) Equilibrium shifts to the left; reaction is endothermic. (iii) Equilibrium shifts to the right, le’charteliers principle removal of product.

(c)

Con of No2

Reaction Path 7. (a) When ignited propane burns with a blue flame because it is a saturated hydrocarbon (alkane) while propyne

burns with a yellow smoky flame because it is an unsaturated hydrocabon √ (alkyne) H H H

| | |(b) H - CC- C - C- C -H

| | |H H H

(c) I oxidation II R - Propene ( Prop - l-ene) C- Sodium propnoate

III Dehydration IV polypropene

(ii) C3H8 +5O2(g) → 3CO2(g) + 4H2O(l)

(iii) Used to manufacture (i) plastic ropes(ii) plastic crate(iii)Plastic chairs

Page | 247

Chemistry paper 1, 2&3 GITHUNGURI SUB-COUNTY EXAMINATION 233/3 CHEMISTRY PAPER 3 MARKING SCHEME 2016

1. Table 1…………………………………………………………………………………….. (5 marks)Distributed as follows:A. Complete table………………………………………………………………………… (1 mark)

Conditions:-i) Complete table with 3 titrations done (1 mark)ii) incomplete table with 2 titrations done ( ½ mark)iii) incomplete table with 1 titration done ( 0 mark)

Penaltiesi) wrong arithmetic/subtractionii) inverted tableiii) burette reading >50unless explained (50+)iv) unrealistic values i.e values less than 1cm3 or in hundredsNB: penalize ½ mark once for one for all

B Use of decimals (tied to the 1st and 2nd row only…………………………………… (1 mark)i) Accept 1 or 2 decimal places used consistently otherwise penalize fullyii) If 2 decimal places are used the 2nd must be a 0 or a 5 otherwise penalize fullyiii) Accept inconsistency in the use of zero’s e.g. 0, 0.0, and 0.00

C Accuracy…………………………………………………………………………… (1 mark)Compare the candidate’s correct titre with the teacher’s valueConditions;-i) If at least one titre value is within 0.1 of teachers value award (1 mark)ii) If no value is within 0.1 of the teacher’s value but there is one within 0.2 award (½ mark)iii) If no value within 0.2 award... (0 mark)NB: where the candidate has wrong arithmetic use the correct worked out value to award.

D. Principles of averaging……………………………………………………………... (1 mark)Values to be averaged must be within 0.2 of one anotheri) If three consistent titres are done and averaged (1 mark)ii) If three titrations are done but only two are consistent and are averaged (1 mark)iii) If only two consistent titrations are done and averaged (1 mark)iv) If three inconsistent done and averaged (0 mark)v) If three consistent titrations done,. two averaged (0mark)vi) If two inconsistent done and averaged (0mark)Penalties Penalize ½ mark for i) No working if answer is correct ii) Rounding off to 1 decimal place (unless it works out to 1 decimal place or to whole number)

E Final accuracy (1 mark)Compare the candidate’s correct average titre with the teacher’s valuei) If within 0.1 (1 mark)ii) If within 0.2 (½ mark)iii) If not within 0.2 (0 mark)NB: where there are two possible average values use the value giving maximum credit Calculations ii) Moles HCl

0.2 x titre½ 1000 = correct ans. accept answer to at least 4 decimal places(Unless it (1mark)

works out otherwise)½- ignore units, but if given must be correct- Penalize wrong transfer of titre value(b) Equation for the reaction

Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l) (1 mark)Penalize ½ mark for wrong or omitted state symbols

(c) (i) Moles Na2CO3in 25 cm3

0.5 x answer (a)(ii) ½= correct answer½ (1 mark)

Page | 248

Chemistry paper 1, 2&3 (ii) Moles Na2CO3 in 250cm3

25 x answer c(i)½ = correct answer½ (1 mark)250

(d) Mass of sodium carbonate in solid A 106 x answer c(ii) above½ = correct answer½ correct units (1 mark)

(e) Percentage of sodium chloride(10 - answer d above)½

10 x 100 = correct answer½ (1 mark)Penalize for answer if above 40% or below 20%

2 Table 2 …………………………………………………………………………….. (4 marks)A. Complete table ………………………………………………………………… (1 mark)

6-7 entries (1mark)4-5 entries (½ mark)

B. Decimal place - accept whole numbers or 1 decimal place, which must be a zero or a fiveC. Accuracy - compare with teachers value , 2o (1 mark)D. Trend - continuous rise ½ mark followed by a fall ½ mark (1 mark)

Graph (3 marks)- Labelling of axes ½ mark- scale ½ mark- more than- Plots 1 mark ½ of grid- shape 1 mark(a)(i) Volume of solution D

- showing ½ mark - correct reading ½ mark

(ii) ∆ T………………………………………………………………………………………….1 mark) - Showing on correct extrapolated graph ½ mark - Correct reading ½ mark

(b) (i) MC∆T……………………………………………………………………………….(1 mark)- correct substitution ½ mark- correct answer ½ mark

(ii) Moles HCl volume in a(i) x 2 M ½ = correct answer ½ mark

1000 (iii) Molar heat of neutralization Hcl…………………………………………………..(2 marks)

Ans b)(i)1 Ans b(ii)

∆ H = -correct answer kJ mol-1

Penalize - ½ mark if -ve sign is missing - ½ mark if units missing or wrong

3. (a) You are provided with solid E. Carry out the following tests and write your observationsand inferences in the spaces provided.

(i) Place one third of solid E on a metallic spatula and ignite using a Bunsen burner flame

observation InferencesBurns with a yellow sooty /smoky flame Long chain hydrocarbon or unsaturated organic

compound, or compound with a high carbon hydrogen ratio Or

C = c -c ≡ c-

(1 mark) Reject - long chain hydrocarbon (1 mark)

(ii) Place all the remaining solid in a boiling tube. Add 5cm3 of distilled water. Shake to dissolve and divide it into4 portions

(I) to the first portion three drops of acidified potassium manganate (VII)

Observation InferencesKMnO4 decolourised R - OHAcceptPotassium Manganate (VII) turns from C= c or -C ≡c - presentpurple to colourless

1 mark 1 mark

Page | 249

Chemistry paper 1, 2&3 (IV) To the second a three drops bromine water.

Observation InferencesBromine water decolourised 1(Accept Orange/yellow/red bromine turnscolourless) C = C

( 1mark) OrC ≡ c (1 mark)

(V) To the third portion all the sodium hydrogen carbonateObservation inferenceseffervescence/bubble H+/ R - COOH1

Accept carboxylic acid for ½ mark(1 mark) ( 1 mark)

(c) You are provided with solid F. Carry out the tests below and record your observations and inferences in the spacesprovided. Place all the solid F in a boiling tube. Add 10cm3 of distilled water. Divide into four portions.observation inferencesSolid dissolves to form a colourless Absence of coloured ions e.g. Cu2+, Fe2+ Fe3+ ½solution½ mark mark

(i) To the first portion, add aqueous hydroxide drop wise until in excess.

observation InferencesNo white ppt formed, even in excess Zn2+, Al3+, Pb2+, Mg2+. Ca2+ absent

Any 3 ions1(1 mark) Only 2 ion

Reject Ba2+ absent (1 mark)

(ii) To the second portion add 5 drops of barium nitrate, followed by 3 drops of dilute nitric(V) acid

Observation inferencesWhite ppt ½ formed. CO32-½ or SO32- ½ presentPpt dissolves on ½ addition of nitric (v) (1 mark)acid (1 mark)

iii) To the third portion add 3 drops of acidified sodium dichromate (VI) solutionObservation inferencesK2Cr2O7 changes1 from orange to green SO32- 1 present(1 mark) (1 mark)

Page | 250

Chemistry paper 1, 2&3 MURANG’A SOUTH SUB-COUNTY MULTILATERAL EXAMINATION 2016 Kenya National Examination Council

233/1 CHEMISTRY PAPER 1 (THEORY) TIME: 2 HOURS JULY/AUGUST 2016

1. a) Three isotopes of Magnesium has mass numbers 24, 25 and 26. What is the mass number of the most abundant isotope ofMagnesium? Explain. (2mks)b) Define the term isotope. (1mk)

2. a) Define hard water. (1mk)b) The structure below represents two cleansing agents.

Which of the above cleansing agent would be suitable for washing in hard water? Give a reason.

(2mks)3. The heat of neutralization of a strong acid is usually 57.4kJmol-1, whereas that of a weak acid is less than 57.4kJmol-1 .

Explain (2mks)4. When an electric current of 0.5A was passed through a molten chloride of J for 32 minutes and 10 seconds, a mass of 0.44g of

J was deposited at cathode.1F = 96500Ca) Calculate the quantity of electricity used. (1mk)b) Determine the value of x if the ion of metal J is represented as Jx+ (2mks)

5. Your friend’s clothes have caught fire. Inorder to extinguish the fire you decide to cover with a damp blanket. What is thepurpose of the clamp blanket? (1mk)

6. Calculate the number of Calcium atoms in 10g of calcium.(Ca = 40, Avogadro number = 6.0 x 1023) (1mk)

7. The table below shows the pH values of some solutions.Solution J K L M NpH 6 13 2 10 7

a) Which solution is likely to be:i) Potassium hydroxide (1mk)ii) Lemon juice (1mk)b) Explain why a solution of hydrogen chloride gas in methyl benzene was identified as N. (1mk)

8. A piece of burning magnesium ribbon was placed in a gas jar full of nitrogen gas. The product Q formed was then reactedwith water.a) Write the chemical formula for the product Q. (1mk)b) Write the equation for the reaction between product Q and water. (1mk)c) Using dot (•) and cross (X) diagrams to represent electrons, draw the structure to show bonding in a nitrogen

molecule. (N = 14) (1mk)9. How would the following pair of compounds be chemically distinguished? CH3COOH and CH3CH2OH.

(2mks)10. Name the products of electrolysis of fused copper (II) chloride using carbon electrodes.

Anode ( ½ mk)Cathode ( ½ mk)Explain (1mk)

11. Zinc metal can be used in the laboratory to prepare hydrogen gas from an appropriate mineral acid while copper metal cannot.Explain. (1mk)

12. a) State one factor that can determine stability of an atom. (1mk)

b) Radioactive polonium -216 decays as shown below.

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Chemistry paper 1, 2&3

Find the value of M and N. (2mks)c) If after 112 days 1/16 of Polonium remained, calculate the half-life of polonium. (2mks)

13. When bromine gas reacts with aqueous sodium hydroxide an equilibrium is established as shown below.Br2(aq) + 2OH-(aq) Br-(aq) + OBr-(aq) + H2O(l)

(Brown) ColourlessWhat observation would be made if a few drops of dilute sulphuric (VI) acid were added to the equilibrium mixture? Explain.

(2mks) 14. One compute combustion of 0.5g of an organic compound P (containing only carbon, hydrogen and oxygen) 0.733g of carbon

(IV) oxide and 0.3g of water were produced. Determine the empirical formula of P. (3mks)

15. Compare the atomic sizes of sodium and magnesium. Explain. (2mks)16.

a) Name gas X. (½ mark)b) Write an equation for production of gas x in the set-up. (1mk)c) It’s hat to test whether gas x supports burning using a glowing splint. Explain. (2mks)

17. When solid M is dissolved in water, it dissolves to form a blue solution. Addition of ammonia solution forms a blueprecipitate which dissolves in excess to form a deep blue solution. Write the formula and name of the ion responsible for thedeep blue solution. (2mks)

18. The diagram below represents the structure of aluminium chloride.a) Identify the bonds labelledM (½ mark)N (½ mark)b) What is the difference between bonds M and N? (1mk)

19. a) Define hydration energy. (1mk)b) Given that hydration energies of Ca2+ and Cl- are -1891kJmol-1 and - 384kJmol-1 respectively and that the lattice energyof calcium chloride is +2237kJmol-1, calculate the molar enthalpy change of solution of calcium chloride. (3mks)

20. The diagram below shows an experiment involving chlorine water.

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Chemistry paper 1, 2&3 a) State and explain the observations made after 24 hours. (2mks)b) Write an equation to show the formation of gas A. (1mk)c) State one use of chlorine gas. (1mk)

21. The solubility of salt Y at 600C is 40g/100g of water and 48/100g of water at 1000C.a) How much salt Y would saturate 190g of water at 1000C. (1½ mark)b) 150g of a saturated solution of Y is 1000C is cooled to 600C. Calculate the mass of Y that crystallizes.

(11/2mks)22. The diagram below shows the appearance of two pieces of paper placed in different parts of a non-luminous flame of a

Bunsen burner and removed quickly before they caught fire.

a) What do the experiments show about the outer region of the flame? (1mk)b) From the above experiment, which part of the flame is better for use in heating? Give a reason.

(2mks)23. Steam is passed over heated magnesium as shown in the diagram below.

a) State one observations that will be made in the tube as heating is carried out. (1mk)b) What substance is being burnt at A? (1mk)c) Write a balanced chemical equation to show the reaction which takes place in the combustion tube.

(1mk) 24. The volume of a given mass of a gas is 250cm3 at 270C and 720mmHg pressure. What will be the volume of the gas at s.t.p.

(3mks) 25. Given the equation N2(g) + 3H2(g) 2NH3(g) DH= -92kJmol-1

Explain what happens to the position of the equilibrium whena) Temperature is raised. (1mk)b) Pressure is changed. (2mks)

26. State and explain the observations made when a few drops of concentrated sulphuric (IV) acid is added toa) Hydrated Copper (II) sulphate. (2mks)b) Sugar (2mks)

27. Study the flow chart below and answer the questions that follow.

a) Given that solid N burns in air with a red flame. Identify:-i) Cation present in solid N (½ mark)ii) Metal oxide L (½ mark)

Page | 253

Chemistry paper 1, 2&3 iii) Gas X (½ mark)

b) Write down the formula of the anion present in solid N. (½ mark)28. Determine the volume of 2.0M NaOH which when diluted to 250cm3 would produce a 0.8M NaOH solution. (2mks)29. Explain how you would obtain pure ammonium chloride from a mixture of lead sulphate and ammonium chloride? (2mks)30. a) Carbon exhibits allotropy. Name one element other than carbon that has the same characteristic.

(1mk)b) In terms of structure explain why graphite conducts electricity while diamond does not? (2mks)c) Define allotropy. (½ mark)

MURANG’A SOUTH SUB-COUNTY MULTILATERAL EXAMINATION 2016 Kenya National Examination Council

233/1 CHEMISTRY PAPER 1 (THEORY) TIME: 2 HOURS Marking scheme

1. a) The ore of atomic number 24 (1mk). Because it is closer to R.A.M (24.3) that means it contributes to R.A.M more than theother two.b) Atoms of the same element with the same number of protons but different number of neutrons. (1mk)

2. a) Water that does not lather easily with soap. (1mk)b) A (1mk) - does not form scum with hard water (1mk)

3. Weak acid is slightly ionised.(1mk) Some heat is absorbed during ionisation of an unionised acid. (1mk)4. a) Q = It

= 0.5 x 1930sec = 965C

b) Jx+(l) + Xe- →J(s) 44g

965C → 0.44g ? 44g

= 44 x 965 1/2 = 96500C

0.44x x 96500 = 96500 x = 1

96500 96500 charge = 1+

5. To cut the supply of oxygen gas.6. 40g contains 6.02 x 1023 Arogadros number

10g ?= 1.505 x 1023 atoms.

7. a) i) K ( 1mk)ii) J (1mk)b) Hydrogen chloride gas in methyl benzene, does not ionise to form an acidic solution. (1mk)

8. a) Mg2N2 (1mk)b) Mg3N2(s) + 6H2O(l) → 3Mg(OH)(aq) + 2NH3(g) (1mk)

c)

9. Ethanoic acid (CH3COOH) reacts with sodium carbonate to liberate carbon (IV) oxide while ethanol (CH3CH2OH) doesnot. (1mk)

10. - Copper metal Copper chloride when fused- Chloride gas (molten) in a binary electrolyte.

11. Copper metal is below hydrogen in the reactivity series hence it cannot displace hydrogen from acids. (1mk)12. a) The ration protons to neutrons in the nucleus of an atom. 1mk

(b) 216 = 208 + 4m + 0 84 = 82 + 2m - n but m = 24m = 8 :. 82 + 4

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Chemistry paper 1, 2&3 m = 2 = 84 = 86 - n

-n = -2n n = 2

c)

4 half-lifes = 112 days 1 half life ??

1 x 112 = 28 days (1/2mk)4

13. Brown colour would intensity (1mk)OH- removed by addition hence backward reaction triggered to replace OH-

14. Since 12g of carbon are present in 1 mol = (449) CO2Mass of carbon in 0.733g CO2 = 12 x 0.733g

44 = 0.1999g = Mass of carbon in P

Since 2g of hydrogen are present in 1mol (=18g) H 2O

Mass of hydrogen in 0.300g of H2O = 2 x 0.300g18

= 0.333g = Mass of hydrogen in P

Hence mass of oxygen in P = 0.5 - 0.1999 = 0.0333 = 0.2668g (1/2mk)

Atoms C H OMass 0.1999 0.0333 0.2668Moles 0.1999 0.0333 0.2668

12 1 16

0.01666 0.0330 0.016680.01666 0.01666 0.01666

1 : 2 : 1Hence empirical formula CH2O

15. Sodium has a bigger atomic size than magnesium 1mk. Atomic radius decreases across period because of the increase inthe nuclear charge

16. a) NOb) 8HNO3(aq) + 3Cu(s) → 3Cu(NO3)(aq) + 2NO(g) + H2O(l) 1mkc) Readly combines with oxygen to form nitrog en (IV) oxide. (1mk) Because it is higly unstable. (1mk)

17. [Cu(NH3)4]2+ Tetra ammine copper (II) ions.)18. a) M - Covalent bond

N - dative bond b) For M, shared electrons are coming from the species. For N, shared electrons are contributed by one species.

19. a) This is the energy change that occurs when one mole of gaseous ions become hydrated. (1mk) b) Hsol = Lattice energy + Hydrated energy

= -2273 + (-1891) + 2(-384) = -422kJ/mol

20. a) Chlorine water changes colour from yellow to colourless. (1mk)- Chlorine water decomposes to form hydrochloric acid and oxygen.

b) 2HOCl(aq) → 2HCl(aq) + O2(g) 1mkc) - Bleaching agent,

- Treatment of water. Any ( 1mk)21. a) 48 100g of H2O

190g of H2O190 x 48 = 91.2g100

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Chemistry paper 1, 2&3 b) 150 - 100 = 50 - 40 = 10g of crystals

22. a) It is the hottest part.b) The outermost regionCO2 - There is enough oxygen to ensure complete combustion.

23. a) A white solid is formed. 1mkb) Hydrogen gas. 1mkv) Mg(s) + H2O(g) → MgO(s) + H2(g) (1mk)

24. P1V1 = P2 V2 V1 = 250cm3 V2 = ?

T1 T2 P1 = 720mmHg P2 = 760mmT1 = 270 + 273 = 300K T2 = 273K

70 x 250 = 760 x V2 760 x 300 = 720 x 250 x 273300 273 760 x 300 760 x 300

V2 = 215.53cm325. a) Increase in temperature fovours the backward reaction. i.e. the equilibrium shifts to the left. Backward reaction is

Endothermic.b) Equilibrium will shift to the left when the pressure is decreased and to the right when the pressure is increased.Increase in pressure favours the side with few molecules and vise versa. (1mk)

26. a) Turns white (1mk) Removal of water crystallisation to form white anhydrous copper (II) sulphate (1mk)b) The sugar crystallize change to black. (1mk)This is after removal of molecules of water.

H2SO4C6H12O6 → 6C + H2O (1mk)

27. a) i) Ca2+ or calcium ionsii) CaO or calcium oxideiii) NO2 or Nitrogen (IV) oxideb) NO3- or Nitrate ion

28. M1V1 = M2V20.4

2 x V1 = 250 x 0.8 (1mk) = 100cm3 (1mk)

2 2

29. Place the mixture into a beaker and cover with a watch glass containing cold water. (1mk)Heat the mixture gently Ammonium chloride will sublime, to give ammonia and hydrogen chloride that later recombineto form ammonium chloride.

30. a) Sulphur (1mk)b) Presence of delocalised electrons (1mk) in graphite that are absent in diamond. NB: Explanation should touch onstructure and bonding. (1mk)c) Existence of an element in more than one form in the same physical state,

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Chemistry paper 1, 2&3 KIGUMO SUB-COUNTY CLUSTER EXAMINATION 2016 Kenya National Examination Council

233/1 CHEMISTRY PAPER 1 (THEORY) TIME: 2 HOURS JULY/AUGUST 2016 SECTION A Answer ALL the questions on the spaces provided.

1. a) What is meant by term Isomerism. (1mk)

b) Draw an Isomer of pentene. (1mk)2. Consider the metals copper and zinc.

a) Name one ore for each metal Copper: Zinc:

b) Apart from copper being a good conductor of heat and electricity, state any other physical property of copper.(1mk) 3. a) Define the term fuel. (1mk)

b) State two factors to consider when choosing a fuel. (1mk)4. a) State Graham’s Law of diffusion. (1mk)

b) A compound contains 29.1% sodium, 40.5% sulphur and the rest is oxygen. Find the empirical formulae.(Na = 23, S = 32, O = 16) (2mks)

5. a) Calculate the maximum volume of oxygen, measured at s.t.p., that can be obtained by heating a solutioncontaining 8.8g of hydrogen peroxide. (2mks)

b) What is a standard solution. (1mk)6. a) State two methods of removing permanent hardness in water only. (1mk)7. Study the flow chart below and answer the question that follows.

Identifyi) Solid V (1mk)ii) Solution R (1mk)iii) Solution Q (1mk)

8. Crystals of hydrated sodium carbonate (Na2CO3.10H2O) left in open air and changed to a white powder.i) Explain what happens and give the relevant equation. (1mk)ii) Give the name of the process shown above. (1mk

9. A student used the set-up shown in the diagram below inorder to study the reactions of some metals with steam. Theexperiment was carried out for ten minutes.

a) What observation would be made if gas H was ignited. (1mk)b) When the experiment was repeated using lead powder instead of Beryllium very little of gas H was obtained. Give a reasonfor this observation. (1mk)

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Chemistry paper 1, 2&3

c) Name another gas which is used together with hydrogen in welding. (1mk)10. Compare the reactivity of chlorine and bromine. (2mks)11. The table below shows the electrical conductivity of substances A, B and C.

a) Give the type of structure and bonding that is present in substance A. (1mk)b) Which substance is likely to be sodium chloride. Explain. (2mks)

12. Hydrogen Iodide is a product formed when hydrogen reacts with Iodine according to the equations.

H2(g) + H2(g) 2HI(g) ÐH = +52.0KJ/mole

Explain how the following would affect the yield of Hydrogen Iodide.a) Increase the temperature. (1mk)b) A decrease in pressure of the system. (1mk)c) State the Le Chatelier’s principle. (1mk)

13. Explain the following observation made by a form three student.a) Dilute hydrochloric acid does not react with copper metal, but dilute nitric acid does. (1mk)b) Describe briefly how one can distinguish Nitrogen (I) oxide from Nitrogen (II) oxide. (1mk)

14. a) Noble gas are usually unreactive. Explain this phenomena. (1mk)b) Explain the meaning of the term ductility a property found in metals. (1mk)c) Study the diagram below.

Write down the equation for production of gas Q. (1mk)15. The diagram below was used by a student to prepare a certain gas.

a) Write equation taking place in the experiment. (2mks)

b) State why it is advisable to burn the gas. (1mk)

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Chemistry paper 1, 2&3

16. Study the flow chart given below.

a) Name substance B. (1mk)b) Give one us of product C. (1mk)c) Write the equation between substance B to form substance C. (1mk)17. The diagram below was used to prepare and collect Sulphur (IV) oxide gas.

a) Identify solid M. (1mk)b) State two properties of SO2 that makes possible to be collected in the method shown. (1mk)c) What are the optimum conditions of conversion of SO2 to SO3. (1mk)

18. During an electrolysis of Zinc sulphate using inert electrodes, a current of 0.5A was passed for 40 minutes on a steadycurrent.a) Write down the equation at the cathode. (1mk)b) Calculate the volume produced at the cathode given that 1F = 96,500c, MGV = 22.4 litres.

(2mks)19. a) Half-life of a radio-active elements is 30 days. Calculate the time required for its activity 37.5 counts per minute.(2mks)

b) Differentiate between an alpha and beta particles. (1mk)20. a) What type of bond is formed when Beryllium and oxygen react. (1mk)

b) Explain why water fetched in rocky areas tend to boil at higher temperature than distilled water.(2mks)

21. a) Copper (II) Sulphate crystals were placed in a beaker containing water. State and explain theobservations made after two days. (2mks)

b) Describe how you can differentiate between Lead (II) ions and Calcium ions using Sodium chloride. (1mk)22. Ethanol obtained from glucose can be converted to ethene as shown below.

a) Name and describe the processes that take place in step I and step II. (2mks)b) State the importance of producing biodegradable plastics and detergents. _______________________________ (1mk)

23. The table below is a part of the periodic table. The letters are not the actual symbols of the element. Study it and answer thequestions that follows.

To Page | 259

Chemistry paper 1, 2&3

a) Select an element which is the most reactive. (1mk)b) How do the ionic radius of T and S compared? Explain. (2mks)

24. A mixture of substance K (density 0.626g/cm3) and Z (density 0.85g/cm3) was allowed to settle in a container as shownbelow.

a) Which liquid forms layer (I) (1mk)b) Explain your answer in (a) above. (1mk)c) The chromatogram below shoes the constituents of a flower extract. Study it and answer the question that follows.

Give a reason to explain the different positions of red and yellow pigments. (1mk)25. A student was given a mixture of Lead carbonate and sodium carbonate powders. Explain how you would obtain solid

sodium carbonate, (3mks)26. A compound was analysed and found to contain 24.27% carbonate, 4.08% hydrogen and the rest is chlorine. If the molar

mass of the compound is 99.0, calculate the molecular formula.(C = 12, H = 1, Cl = 25.5) (3mks)

27. a) Write down the equation between burning magnesium and carbon (IV) oxide. (1mk)b) Carbon (IV) oxide does not support combustion yet burning magnesium continues to burn;

Explain. (2mks)28. Draw the following structure.

i) 2-bromo-4-methylpent-2-ene (1mk)ii) Two hydrocarbons compounds are represented by the formulae C4H8 and C4H10.

Which of the compounds is saturated;Explain (2mks)

29. The diagram below illustrates an experiment to investigate the conduction of electricity in liquids. Study it and answer the questions that follows.

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Chemistry paper 1, 2&3

a) State one mistake in the set-up. (1mk)b) If the liquid in the beaker was benzene. State what expected at the bulb? Explain (2mks)

KIGUMO SUB-COUNTY CLUSTER EXAMINATION 2016 CHEMISTRY PAPER 1 MARKING SCHEME 1. a) Existence of a compound with the same molecular formula but different structural formula

2. a) Copper pyriteZinc blende

b) Malleable, ductileRed metallic lustre (any)Melting point 11000CDensity 8.9g/cm3

3. a) Substance that undergoes combustion readily and gives out heat energyb) Availability

Cost Storage Pollution effects any (2)Heating value

4. a) Under the same conditions of temperature and pressure the rate of diffusion of a gas is inverselyproportional to the square root of its density.

b) Element: Na S O% of mass 29.1 40.5 30.4R.A.M 23 32 16No. of moles 29.1 40.5 30.4

23 32 161.265 1.266 1.9

Na: S : O1.266 1.266 1.9

divide by1.266 1.266 1.9

smallest 1.266 1.266 1.2661 x 2 : 1 x 2 1.5 x 2

x 2 2 2 3

E.F Na2S2O35. a) Equation

2H2O2(l) → 2H2O(l) + O2(g)2 x 34g → 22.4cm3 at s.t.p

Thus 68g of H2O2 yield 22.4 cm3 of O2 at s.t.pPage | 261

Chemistry paper 1, 2&38.8g of H 2O2 yield ?

= 22.4 x 8.868

b) A solution whose concentration is known.6. - Distillation

- Addition of sodium carbonate (Na 2CO3)- Use of ion - exchange method (any 2)

7. i) Sulphur (S)ii) Iodine solution (I 2(aq))iii) Pottassium chloride (KCl)

= 2.89dm3 of O2 at s.t.p

8. i) Sodium carbonate looses water of crystallisation to the atmosphere.Na2CO3.10H2O → Na2CO3(s) + 10H2O(l)(ii) efflorescent

9. a) The gas burns with a ‘pop’ sound b) Lead is least reactive compared to Berylium thus the reaction is slow hence little amount of hydrogen gas. c) Oxygen

10. Chlorine is more reactive than bromine These is because the electron affinity of chlorine is higher than that of bromine. Reactivity of halogens decrease down the group.

11. a) Metallic bondb) B; Since doesn’t conduct in solid, but conducts in molten and in aqueous

12. a) More of HI forms i.e. Favours the forward reaction.b) Has no effect, molecules are equal on both sides of the system.c) When a change in conditions is applied to a system in equilibrium , the system moves so as to oppose the change.

13. a) Dilute nitric (V) acid is a very powerfulOxidizing agent hence it can react with least reactive metals. b) Nitrogen (I) oxide relights a glowing splint and has a faint sweet smell, while nitrogen (II) oxide is very unstable.

14. a) Noble gases have their outermost energy level being filled-up hence do not require to loose or gain as the unreactive. b) Property of metal being drawn into wire c) 2HOCl(aq) → 2HCl(aq) + O2(g)

15. a) i) 2H2(g) + O2(g) → 2H2O(l)

ii) 2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)

b) Mixture of the gas with in explosive hence burned for safety reasons16. a) Ca(OH)2 / Calcium hydroxide

b) Removal of water hardness - Test the presence of CO2 gas (any one )- Raising of pH in acidic soils c) Ca(OH) 2(aq) + 2NH4Cl(aq) →CaCl2(aq) + 2NH4OH(aq)

17. a) Copper / Cu b) Denser than air / Insoluble in liquid x c) Temperature 4500C

Catalyst V 2O5 / Vanadium (V) oxide Pressure 2-3 atmospheres

18. a) 4H+(aq) + 4e-(aq) → 2H2(g)

b) Q = IT= 0.5 x 40 x 60 4F -----> 2 moles 1 mole -----> 22.4 litres= 1200C 4 x 96500 ---> 2 moles 0.00622 ---> ?

1200c ---- 2 x 1200 22.4 x 0.0062296,500 x 4 1

= 0.00622 moles = 0.1393 litresor 139.3cm3

19. a)

No. of half-life 7Page | 262

Chemistry paper 1, 2&3 @ half-life 30 days Time = 7 x 30

= 210 days

b) +vely charged , B +vely charged any (1) high ionizing power in air, than beta are deflected towards -ve plate, Beta towards the plate lower penetrating power than B - particles

20. a) i) Ionic / Electrovalent bondb) Water from rocky have dissolved salts (impurities) than tend to raise the boiling points of these water.

21. a) A blue solution was formed, copper (II) sulphate is soluble in water.b) NaCl with Pb2+ it will form a white ppt due to formation of PbCl2 which is insoluble but with Ca2+ will not.

22. a) Step I : FermentationII: Dehydration

b) Reduces pollution of the environment. 23. a) P

b) S has a bigger ionic radius compared to T; sine T forms ions by loosing electrons and S forms ions by gaining electrons. 24. a) Z

b) Z is denser than K hence settles at the bottom.c) Yellow is highly soluble and less sticky while red is less soluble, but highly sticky.

25. Add water to the mixture and stir. Na2CO3 dissolve while PbCO3 does not. Filter to saturation and allow to cool forcrystallization of Na2CO3 to take place.

26. Element C H Cl% Mass 24.27 4.08 71.65 EF = CH2ClR.A.M. 12 1 35.5No of moles 24.27 4.08 71.65 M = 99

12 1 35.5 12 + 2 + 35.5

2.0225 4.08 2.018 = 99Divide by 2.0255 4.08 2.018 49.5Smallest 2.018 2.018 2.018 = 2

1 2 1M.F. = (CH2Cl)2

= C2H4Cl227. a) 2 Mg(s) + CO2(g) → 2MgO(s) + C(s)

b) Burning Mg produces alot of heat, hence decomposes CO2 into C and oxygen, then O2 is set free and combines withoxygen to form the white solid and black specks of carbon.

28. a)

b) C4H10, it does not contain a double bond or tripple bond.29. a) Electrode L and Electrode K are connected.

b) No lightDoes not contain ions which are responsible for electrical conductivity.

Page | 263

Chemistry paper 1, 2&3 GATANGA FORM FOUR END OF TERM II EXAMINATION 2016Kenya National Examination Council 233/2 CHEMIS TRY (THEORY)PAPER 2

1. The table below shows elements in the periodic table. Use it to answer the questions that follow. The letters are not the actualsymbols of the elements.

a) i) Write the electron arrangement of elements; B and Aii) Write the formula of the compound formed between the elements B and E. (1mk)

b) Element K has atomic number 14. Indicate by use of tick ( ) the position of this element in the table above. (1mk)c) i) he ionization energy of A is higher than that of G. Explain. (1mk)

ii) The atomic radius of C is larger than that of D. (1mk)iii) Compare the reactivity of elements A and B.

Explain your answer. (2mks)d) i) State the name of the group to which elements F and H belong. (1m

ii) Give one use of any of the elements of in group in d(i) above. (1mk)e) The chloride of B is ionic, while the chloride of C is covalent. Explain this observation. (2mks)2. (a) A student wrongly categorised air as a compound and not as a mixture. Give two reasons as to why the student was

wrong. (2mks)(b) The table below shows the results obtained when four solvents were used to separate a dye. Study the results and use them to

answer the questions that follow.Solvent Number of

Solute componentsA 5B 1C 0D 2

i) Identify the most suitable solvent for this separation. Give a reason for your answer. (2mks)ii) What does the result of the solvent C tell us about the dye? (1mk)c) The chromatogram below was obtained from a plant extract. Use it to answer the questions that follow.

i) Name line W (1mk)ii) What does the dotted line represent? (1mk)iii) State with a reason the least soluble dye in the moving solvent. (1mk)d) Below is a list of major component of crude oil and their boiling points.

Component Boiling point (0C)Bitumen Above 400Lubricating oil 350 - 400Petrol 40 - 175Gases Below 40

i) What is the name of the process by which the constituents of crude oil can be separated? (1mk)

Page | 264

Chemistry paper 1, 2&3 ii) Give one use of the gases component. (1mk)iii) Give the order by which the components are obtained from the mixture, starting with the first. (1mk)

3. An impure solid of magnesium carbonate weighing 9.5g was placed in a beaker containing 50cm3 of dilute nitric (V) acid.The volume of carbon (IV) oxide evolved was recorded at 20 seconds interval in the table below.Time from start of Reaction (sec) 0 20 40 60 80 100 120Volume of CO2 at s.t.p (cm3) 0 650 900 1070 1100 1120 1120

3. a) Write the equation for the reaction between magnesium carbonate and nitric (V) acid. (1mk)b) i) Plot a graph of volume of carbon (IV) oxide (y-axis) against time. (3mks)

ii) From the graph; calculate the rate of reaction betweenI 20 seconds and 40 seconds interval. (2mks)II 40 seconds and 60 seconds interval. (2mks)c) Explain the difference in the reaction rates in I and II. (1mk)d) Why was there no further increase in the volume of carbon (IV) oxide gas after 100 seconds? (1mk)e) How many moles of carbon (IV) oxide were in the maximum volume produced from this reaction? (Molar gas volume at

s.t.p. = 22.4 litres) (1mk)f) What mass of magnesium carbonate will have reacted with the acid after 100 seconds.

(Mg = 24, C= 12, O = 16) (2mks)g) Determine the percentage purity of magnesium carbonate. (2mks)h) Calculate the original concentration of the nitric (V) acid in moles per litre. (2mks)

4. The flow chart below shows some reactions starting with lead (II) nitrate. Study it and answer the questions that follow.

a) i) State the condition necessary in step 1. (1mk)ii) Identify;I Gas Q (1mk)II The acid products S and R (2mks)

b) Write the balanced chemical equations for the reactions in;i) Step3 (1mk)ii)Step 4 (1mk)

c) i) The reaction between lead (II) nitrate and dilute sulphuric (IV) acid starts but stops almost immediately. Explain this observation. (2mks)

ii) Name a suitable reagent that can be reacted with concentrated sulphuric (IV) acid to produceNitric (V) acid. (1mk)

d) In the industrial extraction of lead metal, the ore is first roasted in a furnance. The solid mixture obtained is then fed intoanother furnance together with coke, limestone and scrap iron. State the function of each of the following in this process:a) Coke (1mk)b) Limestone (1mk)c) Scrap Iron (1mk)

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Chemistry paper 1, 2&3 5. a) Candle wax is mainly a hydrocarbon. What is a hydrocarbon? (1mk)

b) Name the following compounds.i)

c) Castor oil extracted from castor seeds is found to change the colour of acidified potassium managanate (VII) .i) State the colour change. (1mk)ii) Explain why castor oil reacts with acidified Potassium mangate (VII) to cause the colour change. (1mkd) Study the reaction scheme below and use it to answer the questions that follow.

ii) Name the process in;Step I (1mk)Step II (1mk)

ii) State the reagent necessary for the process inStep II (1mk)Step III (1mk)

iii) Name the type of reaction taking place in step III (1mk)6. The set up below was used during the electrolysis of acidified water using inert electrodes.

a) Why is the water acidified (1mk)b) What material are the electrodes made of? (1mk)

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Chemistry paper 1, 2&3 c) Identify: Gas A (1mk)

Gas B (1mk) d) On the diagram label;

The Anode:(1mk) The cathode (1mk)

e) During the electrolysis a current of 2 amperes was passed through the acidified water for 21/2 hours. Calculate the volume of gas B produced at rtp. (1 Faraday = 96500C, Molar gas volume at r.t.p = 24000cm3) (3 mks)

7. a) Rhombic sulphur and monoclinic sulphur are allotropes of sulphur. Define Allotropy. (1mk)b)Give two other elements that exhibit allotropy. (1mk)c) Study the flow chart below and answer the questions that follow.

c) Name (i) Compound T (1mk)ii) Gas U (1mk)d) The equation below shows the reaction between sulphur (IV) oxide gas and oxygen gas to produce sulphur (VI) oxide in

contact process.2 SO2(g) + O2(g) → 2SO3 D = -197 kJ/mol

i) State two conditions that are necessary for maximum production of SO3. (2mks)ii) Name the catalyst used for this reaction. (1mk)e) State one use of sulphuric (IV) acid. (1mk)

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Chemistry paper 1, 2&3 GATANGA FORM FOUR END OF TERM II EXAMINATION 2016Kenya National Examination Council 233/2 CHEMISTRY (THEORY)PAPER 2

1. a) i) B 2.8.2.E 2.8.7

ii) B2+ E-+2 -12 1x1 x2

BE 2 b) Between C and D in the table c) An atom of G has one more energy level than that of A. The valence eletron is therefore more loosely held by the positive nucleus and thus easier to remove. ii) The atom of D has a bigger / stronger nuclear charge than that of C. The number of energy level pulled is the same. iii) A is more reactive than B. This is because A loses only one electron while B looses two electrons to obtain an octet configuration. More ionisation energy is requird for B to react than is required for A. d) i) Noble gases ii) Helium is used in weather balloons. Neon is used in electric lamps. e) The bond between B and chlorine is ionic formed by transfer of electrons from B to chlorine. On the other hand, the bond between C and chlorine is covalent, formed by equal sharing of electrons, hence a molecular compound.

2. A mixture canbe separated by physical means (eg filtration, distillation etc) a compound cannot. - The components of air are not in definite whole number ratio in a compound, the elements are combined in definite whole number ratios, - A compound is a pure substance whilst air is a mixture of several substances. (any (2 x 1) = 2mks b) i) A : It separates the dye to the greatest number of components ie separates the dye the most. ii) The dye is insoluble in the solvent C c) i) Baseline / Origin ii) The solvent front iii) Yellow - It moves the shortest distance from the origin. d) i) Fractional distillation ii) The gases are used as a fuel iii) Gases, Petrol, Lubricating oil, Bitumen

3. a)MgCO3 (s) + 2HNO3(aq) → Mg (NO3)2(aq) + CO2(g) + H2O(l)b) - Scale (at least 1/2 page used)

Label the axis (Both)- Plotting (1mk)Smooth curve (1mk)

ii) 900 - 650 = 250 = 12.5cm3/sec40 - 20 20Working on the graph must be shown

II1070 - 900 = 170 = 8.5 cm3/sec

60 - 40 20Working on the graph must be shown

c) The rate of reaction decreases as time progresses, since the concentration of reactants reduces as the reaction progresses.d) The reactions has reached completion//the reactants are used up.e) 1 mole of CO2 occupies 22400cm3

? ,, ,, ,, 1120 cm3? = 1120cm3 x 1 mole = 0.05 mole of

22400cm3 CO2

f) Mole ratio of MgCO3 : CO21 : 1? : 0.05

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Chemistry paper 1, 2&3

.: Moles of MgCO 3 = 0.5 x 1 = 0.5 mole of MgCO3 1

Mass of MgCO 3 used = R.F.M of x Number of moles MgCO3

= [24 + 12 = (16 x 3)] x 0.05= 84 x 0.05 = 4.2g= 4.2g of MgCO3

g) % purity of MgCO3 = 4.2 x 1009.5

= 44.21% h) Mole ratio of MgCO3 : HNO3 1 : 2

0.05 : ?

.: Moles of HNO 3 used = 0.05 x 2 = 0.1 mole 1

==> 0.1 mole of HNO 3 is in 50cm3 ? 1000cm3? = 0.1 x 1000 = 2.0M

50 4. a) i) Heating

ii) Oxygen gasII S : Nitric (III) acid

R : Nitric (V) acid

b) PbO(s) + H2(g) → Pb(s) + H2O(l)

II) 2HNO2(aq) + O2(g) → 2HNO3(aq)c) i) The reaction produces Lead (II) sulphate which is not soluble in water. Thus, the lead (II) sulphate forms an insoluble layer which prevents further contact between lead (II) nitrate and sulphuric (VI) acid. Hence, the reaction stops. ii) Potassium Nitrate d) a) Coke reduces lead (II) oxide to lead metal b) Limestone produces calcium oxide which combines with silica to form calcium siliate and hence removes silicaimpurities.c) Scrap Iron reduces any remaining lead (II) sulphite to lead metal.

5. Hydrocarbon - a compound that is made up/contains carbon and hydrogen atoms only.b) i) 3 - Methylbut-2-eneii) Proplylethanoate iii) Pentane c)(i) From purple to colourless. ii) Potassium manganate (VII) to cause the colour change. d)Step I -Hydrogenation / Addition of hydrogen Step II - Polymerisation ii) Step II - Nickel catalyst Steip III - Hydrogen chloride , HCl iii) Addition

6. a) To imporve its conducting propertiesb) Graphite or Platinum c) Gas A - Hydrogen gas Gas B - Oxygen gas d) Anode - Electrode on the right

(Labelling should be on the diagram) Cathode: Electrode on the left (Labelling should be on the diagram) e) Gas B = Oxygen

4OH-(aq) → 2H2O(l) + O2(g) + 4e-

.: 4 mole of e- produce 1 mole of O2 (24000cm3)

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Chemistry paper 1, 2&3

.: 4F produce 24000cm3 of O2 Q = It

= 2 x 2.5 x 60 x 60= 18000C

(4 x 96500)C produce 24000cm3 of O218,000C produce ?? = 18000 x 24000 = 119.17cm3

4 x 96500= 1119.7cm3 of O2

7. a) Allotropy is the existence of an element in more than one form in the same physical state.b) Carbon- Phosphorous c) Compound T - Copper (II) Sulphide ii) Gas U - Hydrogen Sulphide d) i) High pressure (2-3 atmospheres) - Low temperature (4500C) ii) Platinum / Vanadium (V) oxide e) - Manufacture of dyes and paints - Manufacture of drugs - Dil. H 2SO4 is used as an electrolyte in lead -acid accumulators. any 1

Sodium Nitrate

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