August 2022

Kenya Certificate of Secondary Education 2017 Chemistry paper 1 1. Table 1 shows the atomic numbers and the first ionisation energies of three elements. The letters are not actual symbols of the elements. Use it to answer the questions that follow. (a) Explain the trend in first ionisation energy from A to C. (2 mark) (b) Write the electronic configuration for the ion of C. (1 mark) 2. Calculate the values of X and Y in the following nuclear equation. 239U_> X Th+2 oc+2/3 92 Y (2 mark) 3. The diagram in Figure 1 shows a section of a dry cell. Study it and answer the questions that follow. (a) Name the part labelled B. (1 mark) (b) The part labelled A is a paste. Give a reason why it is not used in dry form. (1 mark) (c) What is the purpose of the zinc container? (1 mark) 4. The empirical formula of lead(II) oxide was determined by passing excess dry hydrogen gas over 6.69g of heated lead(II) oxide. (a) What was the purpose of using excess dry hydrogen gas? (2 marks) (b) The mass of lead was found to he 6.21g. Determine the empirical formula of the oxide. (Pb = 207.0 0 = 16.0) (2 marks) 5. The set-up in Figure 2 was used to prepare a sample of ethane gas. Study it and answer the questions that follow. 6. (a) State Charles’ Law. (1 mark) (b) Explain why the pressure of a fixed mass of a gas increases, when the volume of the gas is reduced at constant temperature. (2 marks) 7. A sample of water is suspected to contain sulphate ions. Describe an experiment that can be carried out to determine the presence of sulphate ions. (3 marks) 8. (a) State one characteristic of a reaction where equilibrium has been attained. (1 mark) (b) The following equation is in a state of equilibrium: C D Use it to sketch a graphical representation of concentration against time in seconds for the equilibrium. (2 marks) 9. Copper(II) ions react with excess aqueous ammonia to form a complex ion. (a) (i) Write an equation for the reaction that forms the complex ion. ( I mark) (ii) Name the complex ion. ( I mark) (b) Explain why CH4 is not acidic while HCl is acidic yet both compounds contain hydrogen. (1 mark) 10. 20 cm3 of ethanoic acid was diluted to 400 cm3 of solution. Calculate the concentration of the solution in moles per litre. (C = 12.0 ; H = 1.0 ; 0 =16.0) (Density of ethanoic acid = 1.05 g/cm3) (3 marks) 11. An oxide of element K has the formula 1(205. (a) Determine the oxidation number of K. (1 mark) (b) To which group of the periodic table does K belong? (1 mark) 12. Potassium nitrate liberates oxygen gas when heated. Draw a diagram of a set-up that shows heating of potassium nitrate and collection of oxygen gas. (3 marks) 13. Explain the observation made when chlorine gas is passed through a solution of potassium iodide. (3 marks) 14. Using the elements chlorine, calcium and phosphorus: (a) Select elements that will form an oxide whose aqueous solution has a pH less than 7. ( I mark) (b) Write an equation for the reaction between calcium oxide and dilute hydrochloric acid. (1 mark) (c) Give one use of calcium oxide. ( I mark) 15. Starting with copper, describe how a pure sample of copper(II) carbonate can be prepared. (3 marks) 16. In an experiment, concentrated nitric(V) acid was reacted with iron(II) sulphate. State and explain the observations made. (2 marks) 17. The flow chart in Figure 3 shows the process of obtaining a sample of nitrogen gas. Study it and answer the questions that follow. (a) Identify X (I mark) (b) Write an equation for the reaction with heated copper turnings. (1 mark) (c) Name an impurity in the sample of nitrogen gas. ( I mark) 18. The set-up in Figure 4 can be used to prepare nitrogen(II) oxide. Use it to answer the questions that follow. (b) When the gas jar containing nitrogen(II) oxide is exposed to air, a brown colour is observed. Explain. (1 mark) (c) Write an equation for the reaction which occurred in the flask. (1 mark) 19. The following procedure was used to investigate the temperature changes that occur when sodium hydroxide solution is added to dilute hydrochloric acid. (i) Place the acid in a glass beaker and record its temperature. (ii) Add a known volume of sodium hydroxide solution. (iii) Stir the mixture and record the highest temperature reached. (iv) Repeat steps (ii) and (iii) with different volumes of sodium hydroxide solution. (a) State two factors that must be kept constant in this experiment (1 mark) (b) Explain how the use of a polystyrene cup will affect the results. (1 mark) 20. Study the flow chart in Figure 5 and answer the questions that follow. (a) Identify substances K and L. K: (1 mark) L: (1 mark) (b) Name one reagent that can be used to carry out process J. (1 mark) 21. The atomic numbers of some elements P, Q, R and S are 6, 8, 12 and 17 respectively. (a) Draw the dot (•) and cross (X) diagrams for the compounds formed when: (i) R and Q react (1 mark) (ii) P and S react. (1 mark) (b) Explain why the melting point of the compound formed by P and S is lower than that formed by R and Q. (1 mark) 22. (a) What is an inert electrode? (1 mark) (b) State the products formed when brine is electrolysed using inert electrodes. Anode: (1 mark) Cathode: (1 mark) 23. Explain how a student can establish whether a liquid sample extracted from a plant is pure. (2 marks) Anode (1 mark) Cathode (1 mark) 23. Explain how a student can establish whether a liquid sample extracted from a plant is pure. (2 marks) 24. Figure 6 shows part of

Practical 2018 Chemistry paper 3 1. You are provided with: • 0.30 g solid A, magnesium metal • Hydrochloric acid, solution B • 0.15 sodium carbonate, solution C • Methyl orange indicator You are required to determine the: • Enthalpy change, AH per mole, of the reaction between magnesium metal and excess hydrocholoric acid. • Concentration in moles per litre of hydrochloric acid, solution B. Procedure I (i) Using a burette, measure 50.0 cm3 of solution B and place it in a 100 ml plastic beaker. (ii) Measure the temperature of solution B in the beaker after every 30 seconds and record it in Table 1. (iii) At the 90th second, add all of the solid A provided into the beaker, stir with the thermometer and continue measuring and recording the temperature after every 30 seconds. Complete Table 1. Retain the mixture in the beaker for use in procedure II. Table 1 (a) Plot a graph of temperature (vertical axis) against time on the grid provided. (3 marks) (b) Determine the change in temperature, AT, for the reaction. Show the working on the graph. AT . (1 mark) (c) Calculate the heat change, in joules, for the reaction. Assume that for the solution, specific heat capacity is 4.2 Jg K 1 and density is 1.0gcm 3. (2 marks) (d) The relative atomic mass of magnesium is 24.0. Calculate the enthalpy change, AH, of the reaction per mole of magnesium. Indicate the sign of AH. (1 mark) Procedure H (i) Fill a clean burette with the 0.15M sodium carbonate, solution C. (ii) Place all of the mixture in the beaker from procedure I into a 250ml volumetric flask. Add distilled water to the mark and shake thoroughly. Label the mixture as solution D. (iii) Using a pipette filler, pipette 25.0 cm3 of solution D into a 250 ml conical flask and add 2 drops of methyl orange indicator. (iv) Titrate solution D in the conical flask with the sodium carbonate, solution C and record the readings in Table 2. (v) Repeat steps (iii) and (iv) and complete Table 2. Table 2 Observations Inferences (a) Determine the average volume of the 0.15M sodium carbonate, solution C, used. (1 mark) (b) Calculate the number of moles of: (i) sodium carbonate used. (ii) hydrochloric acid in the 25.0 cm3 of solution D. (iii) hydrochloric acid in the 250 cm3 of solution D. (iv) hydrochloric acid that reacted with magnesium metal.(1 mark) (v) total number of moles of hydrochloric acid in the 50.0cm3, solution B. (1 mark) (c) Determine the concentration of hydrochloric aeid in moles per litre, in solution B. (1 mark) 2. You are provided with solid E. Carry out the following tests and record the observations and inferences in the spaces provided. (a) Place about one-third of solid E in a dry test-tube. Heat the solid strongly and test any gas with both blue and red litmus papers. Observations Inferences (b) Place the remaining amount of solid E in a boiling tube. Add about 15 cm3 of distilled water and shake. Divide the mixture into four test tubes each containing about 2 cm3 . (i) To the first portion, add three or four drops of dilute hydrochloric acid (1 mark) (ii) To the second portion, add two or three drops of aqueous barium nitrate.   Observations Inferences (iii) To the third portion, add aqueous sodium hydroxide dropwise until in excess. Observations Inferences (iv) To the fourth portion, add aqueous ammonia dropwise until in excess. Observations Inferences 3. You are provided with solid F. Carry out the following tests and record the observations and inferences in the spaces provided. (a) Place about one-third of solid F on a clean metallic spatula and burn it in a Bunsen burner flame.   Observations Inferences (b) Place the remaining amount of solid F in a boiling tube. Add about 10 cm3 of distilled water and shake. Use the mixture for tests (i) to (iii) below.   Observations Inferences (i) Using about 2 cm3 of the mixture in a test-tube, determine the pH using universal indicator paper and chart.   Observations Inferences (ii) To about 2 cm3 of the mixture in a test tube, add two or three drops of acidified potassium manganate(VII).   Observations Inferences (iii) To about 2 cm3 of the mixture in a test-tube add two or three drops of bromine Observations Inferences  

2018 Chemistry paper 2 1. The diagram in figure I shows some natural and industrial processes. Study it and answer the questions that follows (a) Identify the processes labelled: (2 marks) A — Fermentation B — Dehydration C — Addition polymerization / polymerization D — Saponification (b) State the reagents and conditions required for processes B and D. (i) Process B: Reagent – Concentrated sulphuric(VI) acids Conditions – Temperature of 160°C – l80°C. <(ii) Process D: Reagent – hydroxide / Sodium hydroxide Conditions – Boil / Boiling (iii) Describe how process D is carried out.(2 marks) The vegetable oil is mixed with sodium hydroxide and boiled Solid sodium chloride is added to the resulting mixture, to precipitate out the soap from glycerol. (iv) State two additives used to improve the quality of soap.(1 marks) Perfumeand builders / tetraoxophosphates/dye (c) State the reagents required in steps F and G.(1 marks) Step F – acidified potassium manganate (VII) (iii) Draw the structure of terylene.(1 marks) (d) (i) Name the polymer formed in step C.(1 marks) Polyethene / polythene (ii) State one disadvantage of the polymer formed in (d) (i).(1 marks) It is non-biodegradable hence pollutes the environment; Produces poisonous gases when burnt. 2. Figure 2 is a section of the periodic table. Study it and answer the questions that follow. The letters do not represent the actual symbols of elements   (a) (i) Select elements which belong to the same chemical family.(1 marks) K and J (ii) Write the formulae of ions for elements in the same period.(1 marks) K+ , L<sup+2< sup=””>, M3+</sup+2<> (b) The first ionisation energies of two elements K and M at random are 577 kJ/mol and 494 tel/mol .(1 marks) (i) Write equations for the 1ˢᵗ ionisation energies for elements K and M and indicate their energies.(1 marks) K(g) + k(g)++ e AHA — 494kJ/mol M(g) + M(g)++ e AHA — 577kJ/mol (iii) Write the formula of the compound formed when L and I react.(1 marks) Across the period, size of atoms decreases therefore more energy required to remove electrons from an atom i n its gaseous state hence, 1ˢᵗ ionization energy for M will be greater than that of K. K has lower nuclear charge / attraction than M / K has less protons than M. (iv) Give one use of element V.(1 marks) Being an inert gas, V is used in fluorescent tubes and bulbs. (c) (i) State another group that G can be placcd in Figure 1. Explain. (2 marks) Group 7. Because G can either lose an electron to form G“ or gain an electron to form G. (ii) How do the reactivity of elements J and K compare? Explain. (2 marks) I is more reactive than K because of increase in the size of atoms. As we go down the group, the atoms increase in size so does reactivity. Outer electrons do not experience much nuclear attraction for bigger atoms. OR Reactivity increases down the group, effective nuclear attraction is greater in K than I’ atomic radius of I is greater than that of K. (d) (i) Elements L and M form chlorides. Complete the following table by writing the formulae of each chloride and state the nature of the solutions. (2 marks) LCl2 Neutral MCl3 /M2Cl3 Acidic   (ii) The chloride of element M vapourises easily while its oxide has a high melting point. Explain. (2 marks) Chloride of M vaporizes easily because of weak van der Waals forces between its dimer Its oxide has a high melting point because of strong ionic bond is difficult to break. 3. (a) Complete Table I by indicating the observations, type of permanent or temporary change and name of new compound formed.   (b) Use the set-up in Figure 3 to answer the questions that follow. The flask was covered with a cloth that had been soaked in ice-cold water.   (i) State the observation made on the coloured water. Explain.(2 marks) Coloured water moves towards the flask. Cold cloth contributes to decrease in temperate causing decrease in volume; this creates a vacuum maling the ink tO move towards the flask. (ii) Name the gas law illustrated in Figure 3.(1 marks) Charle’s law (c) Use the standard electrode potentials in Table 2 to answer the questions that follow.   (i) Write the half-cell representation for the element whose electrode potential is for hydrogen. (1 mark) W+(aq)W2(G)/Pt (ii) Arrange the elements in order of reducing power, starting with the weakest reducing agent. (1 mark) U,Z,X,W2V,Y, (iii) Select two half cells which combine to give a cell with the least e.m.f. (1 mark) V2+/V and W+/W2 II Calculate the e.m.f of the half cells identified in (iii) . (1 mark) e.m.f= 0.00- (-0.40) +0.40V 4. An experiment was carried out to prepare crystals of magnesium sulphate. Excess magnesi um powder was added to l00cm’of dilute sulphuric(VI) acid in a beaker and warmed until no further reaction took place. The mixture was filtered and the filtrate evaporated to saturation, then lcft to cool for crystals to form. (a) (i) Write an equation for the reaction.(1 mark) Mg (s) + H2SO4 -> MgSO4 + H2 (ii) Explain why excess magnesium powder was used.(1 mark) To ensure all the acid was used up. (iii) State how completion of the reaction was determined.(1 mark) When effervescence stops and presence of unreacted magnesium. (iv) What is meant by a saturated solution?(1 mark) Saturated solution is one that cannot dissolve any more solute at a particular temperature. (v) Explain why the filtrate was not evaporated to dryness.(2 mark) Because magnesium sulphate is a hydrated salt and evaporation to dryness causes it to lose it water of crystallization / crystals would not be formed because water of crystallization is lost through heating. (b) When bleaching powder, CaOC1„ is treated with dilute nitric(V) acid, chlorine gas is released. This reaction can be used to determine the chlorine content of various samples of bleaching powders and liquids. (i) Write an equation for the reaction of nitric(V) acid with bleaching powder.(1 mark) CaOC12(s) +2HNO3 -> Ca(NO3)2t -> Cl2(g) +H2 (ii)

2018 Chemistry paper 2 1. The diagram in figure I shows some natural and industrial processes. Study it and answer the questions that follows (a) Identify the processes labelled: (2 marks) A………………. B………………. C………………. D………………. (b) State the reagents and conditions required for processes B and D. (i) Process B: Reagent…………….(1 mark) Conditions ………… (l mark ) (ii) Process D: Reagent…………….(1 mark) Conditions ………… (l mark ) (iii) Describe how process D is carried out.(2 marks) (iv) State two additives used to improve the quality of soap.(1 marks) (c) State the reagents required in steps F and G.(1 marks) (iii) Draw the structure of terylene.(1 marks) (d) (i) Name the polymer formed in step C.(1 marks) (ii) State one disadvantage of the polymer formed in (d) (i).(1 marks) 2. Figure 2 is a section of the periodic table. Study it and answer the questions that follow. The letters do not represent the actual symbols of elements (a) (i) Select elements which belong to the same chemical family.(1 marks) (ii) Write the formulae of ions for elements in the same period.(1 marks) (b) The hrst ionisation energies of two elements K and M at random are 577 kJ/mol and 494 tel/mol .(1 marks) (i) Write equations for the 1 ˢ ᵗ ionisation energies for elements K and M and indicate their energies.(1 marks) (iii) Write the formula of the compound formed when L and I react.(1 marks) (iv) Give one use of elemcnt V.(1 marks) (c) (i) State anothcr group that G can be placcd in Figure 1. Explain. (2 marks) (ii) How do the reactivity of elements J and K compare? Explain. (2 marks) (d) (i) Elements L and M form chlorides. Complete the following table by writing the formulae of each chloride and state the nature of the solutions. (2 marks) (ii) The chloride of element M vapourises easily while its oxide has a high melting point. Explain. (2 marks) 3. (a) Complete Table I by indicating the observations, type of permanent or temporary change and name of new compound formed. (b) Use the set-up in Figure 3 to answer the questions that follow. The flask was covered with a cloth that had been soaked in ice-cold water.   (i) State the observation made on the coloured water. Explain.(2 marks) (ii) Name the gas law illustrated in Figure 3.(1 marks) (c) Use the standard electrode potentials in Table 2 to answer the questions that follow. (i) Write the half-cell representation for the element whose electrode potential is for hydrogen. (1 mark) (ii) Arrange the elements in order of reducing power, starting with the weakest reducing agent. (1 mark) (iii) I Select two half cells which combine to give a cell with the least e.m.f. (1 mark) II Calculate the e.m.f of the half cells identified in (iii) I. (1 mark) 4. An experiment was carried out to prepare crystals of magnesium sulphate. Excess magnesi um powder was added to l00cm’of dilute sulphuric(VI) acid in a beaker and warmed until no further reaction took place. The mixture was filtered and the filtrate evaporated to saturation, then lcft to cool for crystals to form. (a) (i) Write an equation for the reaction.(1 mark) (ii) Explain why eKcess magnesium powder was used.(1 mark) (iii) State how completion of the reaction was determined.(1 mark) (iv) What is meant by a saturated solution?(1 mark) (v) Explain why the filtrate was not evaporated to dryness.(2 mark) (b) When bleaching powder, CaOC1„ is treated with dilute nitric(V) acid, chlorine gas is released. This reaction can be used to determine the chlorine content of various samples of bleaching powders and liquids. (i) Write an equation for the reaction of nitric(V) acid with bleaching powder.(1 mark) (ii) Calculate the volume of chlorine produced when 10 g of CaOC1, is treated with excess nitric(V) acid. (Ca = 40.0; O = 16.0; Cl = 35.5; 1 mole of gas occupies 22.4dm3 at s.t.p) (3 marks) (c) Apart from use of chlorine gas in bleaches and water treatment, state two other uses of chlorine gas. (1 mark) 5. (a) The diagram in Figure 4 was used to prepare hydrogen chloride gas which was passed over heated iron powder. (i) Give a pair of reagents that will produce hydrogen chloride gas in flask A. (2 marks) (ii) Name the substance in flask B.(1 marks) (iii) State the observation made in the combustion tube.(1 marks) (iv) Write an equation for the reaction in the combustion tube.(1 marks) (v) Describe a chemical test for hydrogen chloride gas.(1 marks) (b) (i) Identify the gas that bums at the jet.(1 marks) (ii) Explain why the gas in (b) (i) is burned.(1 marks) (c) Give reasons why excess hydrogen chloride gas is dissolved using the funnel arrangement. (2 marks) (d) State what will be observed when the reaction in the combustion tube is complete.(1 marks) (e) Another experiment was carried out where hydrogen chloride gas was bubbled through methylbeiizene and water in separate beakers. The resulting solutions were tested with blue litmus papers and marble chips. (i) Write the observations made in the following table. (ii) Explain the observations in (e) (i).(2 marks) 6. (a) In Kenya, sodium carbonate is extracted from trona at Lake Magadi. (i) Give the formula of trona. (ii) Name the process of extracting sodium carbonate from trona.(2 marks) (b) The flow chart in Figure 5 summarises the steps involved in the production of sodium carbonate. Use it to answer the questions that follow. (i) Name the process illustrated in Figure 5.(1 mark) (ii) Identify the starting raw materials required in the production of sodium carbonate. (2 marks) (iii) Write equations for the two reactions that occur in the carbonator. (2 marks) (iv) Name two substances that are recycled. (v) Identify: Solid X;…………….(l mark) Process W……………(l mark) (vi) Write an equation for the reaction that produces solution Z.(l mark) (vii) Apart from softening hard water, state two other uses of sodium carbonate. (2 marks)

2018 Chemistry paper 1 1. (a) Define a soluble base. (1 mark) A soluble base is a substance that dissociates in water to produce hydroxide ions as the only negative ions. (b) Aqueous solutions of 2M ethanoic acid and 2M nitric(V) acid were tested for electrical conductivity. Which solution is a better conductor of electricity? Explain. (2 marks) Nitric(V) acid. This is because nitric(V) acid is a strong acid and dissociates completely in solution producing many H+ ions. 2. (a) Explain why it is not advisable to prepare a sample of carbon(IV) oxide using barium carbonate and dilute sulphuric(VI) acid. (2 marks) – The reaction starts but soon stops. This is because the insoluble barium sulphate produced forms a coating on the surface of the barium carbonate preventing further reaction and evolution of carbon(IV) oxide gas. (b) State a method that can be used to collect dry carbon(IV) oxide gas. Give a reason. (l mark) – Downward delivery. – Carbon(IV) oxide is denser than air. 3. The following are formulae of organic compounds. Use the formulae to answer the questions that follow: CH3CH CH2OH CH3 OOH CH3CH2CH 2CH CH3CCCH3 (a) Select: (i) two compounds which when reacted together produce a sweet smelling compound. (1 mark) CH CH CH OH and CH.,COOH (ii) an unsaturated hydrocarbon.(1 mark) CHP CCCH (b) Name the compound selected in (a) (ii).(1 mark) But-2-yne 4. One of the allotropes of sulphur is rhombic sulphur. (a) Name the other allotrope of sulphur.(1 mark) Monoclinic sulphur / beta sulphur / prismatic sulphur (b) Draw a diagram to show the shape of the allotrope named in (a) above.(1 mark)   (c) Write an equation for the reaction between concentrated sulphuric(VI) acid and sulphur.(1 mark) S + 2H2SO4 -> 3SO2 + 2H20 5. Describe an experiment to show that group one elements react with cold water to form alkaline solutions. (3 marks) Place a small piece of sodium metal on water in a trough. When the reaction stops, drop a strip of red litmus paper to the resulting solution. The red litmus paper turns blue showing that the resulting solution is alkaline. ( Any indicator used) 6. (a) State Graham’s law of diffusion. (1 mark) The rate of diffiision of a gas is inversely proportional to the square root of its denslty at constant temperature and pressure. (b) Explain why a balloon filled with helium gas deflates faster than a balloon of the same size filled with argon gas. (2 marks) Helium is less dense than argon hence it diffuses out of the balloon faster than argon. 7. 30.0 cm3 of aqueous sodium hydroxide containing 8.0 g per litre of sodium hydroxide were completely neutralised by 0.294 g of a dibasic acid. Determine the relative formula mass of the dibasic acid. (Na = 23.0 ; O = 16.0 ; H 1.0) (3 marks)   8. Study the flow chart in Figure 1 and answer the questions that follow. Gas N forms a while suspension with aqueous calcium hydroxide.(1 mark) (a) Name the anion present in the potassium salt.(1 mark) Carbonate (CO32 ) (b) Write an ionic equation for the formation of solid M.(1 mark) Ba2+(aq) * CO32 (aq) —› BaCO3(S) (c) Give one use of gas N.(1 mark) – Making soft drinks/aerated drinks; – In refrigeration; – In extinguishing fires; – Making baking powder; Manufacture of sodium carbonate; Cloud seeding. 9.An experiment was carried out to determine the presence of substancePQR and S in mixture T.the results obtained are as follows (a) Name the method of sepration illustrated in figure 2 Chromatography/paper chromatography (ii)A substance which is least soluble in the solvent used. Q 10. Using iron filings, describe an experiment that can be conducted to show that oxygen is present in air. (3 marks) Wet a measuring cylinder/gas jar and sprinkle some iron filings on the wet surface. Remove the excess iron filings; Invert the measuring cylinder in a trough of water; – Take the reading of the air column in the measuring cylinder. Leave the set-up for 2 days; Read and record the volume of the air column; 11. (a) Element U has atomic number 12 while element V has atomic number 16. How do the melting points of their oxides compare? Explain. (3 marks) The oxide of U has higher melting point than the oxide of V; This is because the oxide of U is a solid with ionic bonds hence requires a lot of energy to melt; The oxide of V is a gas hence requires little energy to melt/break molecular forces of attraction. 12. When ethene gas is compressed at a high temperature, a solid is formed. (a) Give the name of the solid. (I mark) Polythene / Polyethene (b) Explain why it is not advisable to allow the solid to accumulate in the environment. (2 marks) It is non-biodegradable, hence pollutes the environment. 13. In the Haber process, nitrogen reacts with hydrogen according to the following equation. 3H2(g) + N2(g) 2NH3(g) ; AH = —92 kJ mol** (a) What would be the effect of adding a catalyst on the position of the equilibrium? (1 mark) No effect/does not affect the position of the equilibrium. (b) Explain why it is not advisable to use temperatures higher than 773 K in the Haber process. (2 marks) Forward reaction is exothermic, excessive temperatures would favour the backward reaction therefore lowering the yield of ammonia. 14. Figure 3 shows a set-up used by a student to prepare dry chlorine gas in the laboratory.   Identify three mistakes in the set-up, and give a reason for each. (3 marks) – One reagent is missing, hence reagents provided cannot produce chlorine; – Wrong drying agent — Calcium oxide will react with the chlorine gas; – Incorrect method of gas collection – No gas will be collected / chlorine is denser than air. 15. You are provided with solid potassium hydrogen carbonate. Describe how a solid sample of potassium nitrate can be prepared. (3 marks) Measure a certain volume of dilute nitric(V) acid and place

 Biology Paper 2 Answer all the questions in the spaces provided. 1. In an experiment to investigate the effect of Sodium chloride on the growth rate in a spinach seedling. seeds were treated with different of sodium chloride. The results are as recorded in the table below. (a) From the results in the table above, explain the effect of increasing the concentration of sodium chloride. (3 marks) Increased Sodium chloride concentration/having more sodium and chloride ions solutes decreases osmotic potential/makes water potential more negative outside the seed/seedling in the surrounding solution/the surrounding solution to be hypertonic to the cell sap in the seedling/ seed cells; seeds take in less water by osmosis/are dehydrated/lose water molecules to the surrounding solution; reducing the (growth) enzyme activity, hence reduced growth rate; OWTTE (b) Apart from a ruler, state two other equipment one would need to determine the rate of growth in the roots. (2 marks)   Thread; Marker pen; Dye(c) With a reason, state one other part of the seedling the students would focus on to determine the effect of sodium chloride on growth. (2 marks) (Rate of growth/increase in length of) the shoot tip/apex; It is a region of (active) cell division/growth; (d) State the likely effect on the seedling of increasing the seedling of increasing the concentration of sodium chloride to 2.20 mol/I . (1 mark) The seedling will be dehydrated, hence wither/die 2. The table below shows results of blood cell counts per mm° of blood from a sample of people living at different altitudes. (a) Explain the relationship between:(i) Red blood cells count and the altitude;(3 mark) (i) The number of red blood cells count increase with the increase in altitude; to increase the oxygen carrying capacity (by the hemoglobin molecules in blood); since oxygen concentration is lower at higher altitudes (ii) White blood cells count and the altitude.(3 mark) White blood cells serve to protect the body against harmful micro-organisms/pathogens; the quantities of pathogens or vulnerability of the body to microbial attack is not dependent on the altitude (to be countered by the white blood cells); hence the number of white blood cells’ count is constant at whatever (b) Explain why chances of nose-bleeding increase with altitude in humans. (2 marks) Atmospheric pressure decreases with the increase in altitude; the imbalance between the (outer) atmospheric pressure at high altitude and the internal blood pressure (generated by the heart) results in one nose bleeding at higher altitudes/internal blood pressure is higher than the (outer) atmospheric pressure . 3. (a) State one importance of irritability to living organism. ( 1 mark)   Enables living organisms to avoid dangerous/harmful/harsh climatic/environmental conditions;  Enable living organisms obtain/access favourable environmental conditions (light, water, oxygen); any one(b) ln an experiment, students treated seedlings as illustrated below.   (i) Account for the observations made in seedling 1 (3 marks)(i) Positive phototropism/tip bends towards light light causes migration of auxins (produced at the tip); to darker side of the shoot resulting in faster division of cells/elongation on the darker/ opposite side of the shoot, hence bending towards light; (ii) Explain the similarity in the end results made in seedlings II and II (2 marks) (ii) Both seedlings remain upright; seedling II does not have the tip while in III the tip has been covered by an opaque material preventing light from causing unequal distribution of auxins; (iii) State the likely treatment that would make seedlings II and III respond like seedling I. (2 marks) Fitting an agar block treated with auxins at the decapitated end of seedling II; removing the opaque material covering the tip of seedling III Replacing the opaque cap with a transparent one; 4. In cats, the gene for fur colour is sex-linked. Letter G represents the gene for ginger fur colour while letter B represents the gene for black fur colour in a given cot species. These genes are codominant. Heterozygous females have ginger and black patches of fur rind their phenotype is described as tortoise-shell. (a) With reference to the information given above, what is meant by the term codominance? (1 mark) Both alleles are expressed/shown equally in the phenotype (of the offspring) /non suppresses the other/ gene for ginger and black fur colour express themselves equally in the phenotype of the offspring. (b) Explain why male cats with a tortoise-shell phenotype do not usually occur. (2 marks) The gene for coat colour is sex-linked; contained in the X-chromosome; males have only (inherit) one X-chromosome (from females/mothers)/Y-chromosome does not carry genes; (c) A tortoise-shell female was crossed with a black male. Determine the genotypes and phenotypes of the offspring. (5 marks) 5. A person accidentally touches a hot pan and responds as illustrated in the diagram below. (a) Explain how the response illustrated above occurs. (6 marks)The stimulus/heat/pain is detected by temperature/pain receptors (in the skin/dermis); impulses transmitted along sensory neurone to the Central Nervous System/spinal cord; (chemical) transmission across synapses; to relay neurone; across a synapse to motor neurone/across another synapse /via motor neurone; to muscles/effectors via motor neurone; muscles/effectors contract, (hand moves away); This is known as a reflex action; (b) Explain how auxins are utilised as selective weed killers in agriculture. (2 marks) Selective weed killers contain auxins which are absorbed by the weeds (than desired/beneficial/plants); making the weeds to grow abnormally faster/die out (ahead of the desired plants); SECTION B (40 Marks) Answer question 6 (compulsory) and either 7 or 8 6. The table below shows the rate of product formation for two enzymes, H and J over a range of pH values. (a) On the same axis, plot graphs of the rate of product formation against pH. (8 marks) (b) Account for the rate of product formation for enzyme H between:(i) pH 1.0 and 3.0 (3 marks) Rate of product formation increases with the increase in pH up to the optimum/then decreases; pH 2.0 is the optimum pH value for the activity of enzyme ii; between pH 1 and 2, the enzyme molecules are activated; (ii)

 Chemistry paper 1 1. An atom of element A has mass number 39 and 19 protons. (a) Write the electron arrangements of the atom (1 mark)   2.8.8.1(b) State the period and group to which element A belongs Group 1(½ mark) Period 3(½ mark) (c) State whether the element is a metal or a non-metal. (1 mark)   Metal2. Describe how an increase in concentration increases the rate of a reaction. (2 mark) As the concentration increases, the number of reacting particles increases leading to increase in effective collisions. This leads to increase in the rate of reaction. 3. The flow chart in Figure 1 represents some stages in the extraction of copper metal. Study it and answer the questions that follow. (a) Identify :(i) The copper ore (1 mark)   Copper pyrites/CuFeS2(ii) Process B (½ mark)   Froth floatation(iii) Solid C (½ mark)   Copper(1) suphide/Cu2S(b) Write an equation for the reaction that forms the slag. (1 mark) FeO(s) + SiO2 (s) —+ FeSiO3(I) 4. A monomer has the following structure. CH= CH2 ∣ C6H5 (a) Draw the structure of its polymer that contains three monomers.(1 mark) (b) A sample of the polymer formed from the monomer has a molecular mass of 4992.Determine the number of monomers that formed the polymer (C= 12; H= 1.0). (2 marks) RFM of monomer = (12 x 8) + 8 =104 Numbers of monomers = 4992/104 = 48units 5. Hydrogen has can be prepared by passing steam over heated magnesium ribbon as shown in the figure 2. (a) Write an equation for the reaction that produces hydrogen gas. (I mark)(b) Explain why the delivery tube must be removed from beneath the water before heating is stopped. (1 mark)   To prevent suck-back of water which would crack the boiling tube. Sodium is a very reactive metal hence reacts explosively with steam.(c) Explain why sodium metal is not suitable for this experiment. (I mark)   To prevent suck-back of water which would crack the boiling tube. Sodium is a very reactive metal hence reacts explosively with steam.6. A farmer intended to plant cabbages in his farm. He first tested the pH of the soil and found it to be 3.0. If cabbages do well in alkaline soils, explain the advice that would be given to the farmer in order to realise a high yield.(2 marks)   Add calcium oxide /1ime to raise the soil pH. Calcium oxide is a basic oxide hence dissolves in water in the soil to form alkaline solution that reacts with acidic soil raising soil pH.7. A solution contains 40.3g of substance XOH per litre .250.0cm3of this solution required 30.0cm3 of 0.3M sulphuric(VI)acid for complete neutralisation. (a) Calculate the number of moles of XOH that reacted. (½ mark) H2SO4(g) + 2XOH(aq) —› X SO4(aq) + 2H2 O(l) Moles of H2SO4 = 30 x 0.3/1000 = 0.009 moles Moles of XOH 2 x 0.009 0.018 moles (b) Determine the relative atomic mass of X. (1½ mark) Molarity of XOH 0.018 x1000/25 = 0.72M R.F.M = g /1/molarity = 40.3/0.72 = 55.972 =56 0.72 x +16 +1 = 56 x = 56 – 17 x = 39 8. Table 1 shows the properties of two chlorides, D and E. Table 1 (a) State the type of bond present in:  D Ionic/electrovalent. Covalent (Van der Waals)(b) Explain in terms of structure and bonding, the difference in electrical activity of the chlorides D and E. (1 mark)   Chloride of D giant ionic; when in molten state the ions are mobile hence conducts electric current. E is giant molecular and therefore does not have mobile ions to carry electric current.9. Sulphur(IV) oxide is prepared in the laboratory using the set-up in Figure 3. Study it and answer the questions that follow. (a) Identify substance F. (1 mark)  Dilute hydrochloric acid / dilute HC1 acid Dilute sulphuric (VI) acid/dilute H2SO4(b) Write an equation for the reaction that takes place in the flask. (1 mark) Na2SO3(s) + 2HC1(Sq) SO z(8) + 2NaCl(dQ) + H2O (1) or Na2SO3(s) +H2SO4 (aq) —+ Na SO4 (aq) + H O(l) +SO2(g) (c) State the purpose of liquid G. (1 mark)   To dry the gasThe graph in Figure 4 was obtained when a certain substance was heated and its temperature recorded at regular intervals.   (a) State the purity of the substance. (1 mark)  Impure(b) Explain the answer in (a). (1 mark)   The substance does not have a sharp melting point or boiling point11. Ethene is prepared in the laboratory by dehydration of ethanol. (a) Name a suitable dehydrating agent used in this process. (1 mark)   Concentrated sulphuric(VI) acid Al203 H3PO4(b) State the condition necessary for the reaction to occur. (1 mark)   Temperature 160°C —l80°C(C) Write an equation for the dehydration process. (1 mark) CH3CH2OH H2SO4 CH2CH2 + H2O 12. A boiling yube filled with chlorine was inverted in a trough containing the same solution and the set-up left in sunlight for about 2 hours. (a) State the observation made in the boiling tube ( 1 mark)   The colour of the solution changes from yellow to colourless. Colourless gas collected/ level of solution drops.(b) Explain the observation made in (a) (1 mark) The sunlight decomposed chloric(I) / hypochlorous acid to oxygen and hydrochloric acid. (c) Write an equation for the reaction that occurred in the boiling tube (1 mark) 2HOCl(aq) —+ 2HCl(aq) + 02 (g) 13. 5 g of calcium carbonate was strongly heated to a constant mass. Calculate the mass of the solid residue formed (Ca = 40.0; C = 12.0; 0 = 16.0). (2 marks) CaCO,(s) —› CaO(s) + CO2(g) No. of moles of CaCO3 = 5/100 = 0.05 moles 100 Moles CaO = 0.05 Mass of CaO = 0.05 x 56 = 2.8g 14. During laboratory preparation of oxygen, manganese(IV) oxide is added to reagent 11. (a) Name reagent H. (1 mark)   Hydrogen peroxide(b) State the role of manganese(IV) oxide in this experiment. (1 mark)   Catalyst, to speed up the production of oxygen gas.(c) Write the equation for the reaction that takes place.

2020 Chemistry paper 2

 Chemistry Paper 3 (233/3) 1 You are provided with: – 1.6Og of solid A. a dibasic acid. – Solution B containing 4.75g per litre of salt B. – Aqueous sodium hydroxide. solution C. – Phenolphthalein indicator. You are required to prepare a solution of solid A and use it to determine the:- – Concentration of sodium hydroxide. solution C – React salt B with excess sodium hydroxide and then determine the relative molecular mass of salt B. Procedure I (a) Using a burette, place 25 .Ocm3 of solution B in each of two 250ml conical flasks. Using a pipette and pipette filler, add 25.0cm3 of solution C to each of the two conical flasks. (The sodium hydroxide added is in excess). Label the conical flasks 1 and 2. (b) Heat the contents of the first conical flask to boiling and then let the mixture boil for 5 minutes. Allow the mixture to cool. (c) Repeat procedure (b) with the second conical flask. While the mixtures are cooling, proceed with procedure II. Procedure II (a) Place all of solid A in 21 250 ml volumetric flask. Add about 150cm3 of distilled water, shake well to dissolve the solid and then add water to make up to the mark. Label this as solution A. (b) Place solution A in a clean burette. Using a pipette and pipette filler, place 25 .0cm3 of solution C in a 250ml conical flask. Add 2 drops of phenolphthalein indicator and titrate with solution A. Record your results in Table 1. Repeat the titration two more times and complete the table. Table 1 (4 marks) Calculate the:- (i) average volume of solution A used: (1/2 mark) (ii) concentration in moles per litre of the dibasic acid in solution A; (2 marks) (Relative molecular mass of A is 126). (iii) moles of the dibasic acid used; (1 mark) (iv) moles of sodium hydroxide in 25 .0cm3 of solution C. (l mark) (v) concentration of sodium hydroxide in moles per litre. (2 marks) Procedure III Add 2 drops of phenolpthalein indicator to the contents of the first conical flask prepared in procedure l and titrate with solution A. Record your results in Table 2. Repeat the procedure with the contents of the second conical flask and complete the table. Table 2 (3 marks) Calculate the:- (i) average volume of solution A used; (1/2 mark) (ii) moles of the dibasic acid used; (1 mark) (iii) moles of sodium hydroxide that reacted with the dibasic acid. (1 mark) (iv) moles of sodium hydroxide that reacted with 25 .0cm3 of salt B in solution B; (2 marks) (v) Given that l mole of salt B reacts with 2 moles of sodium hydroxide, calculate the: l. number of moles of salt B in 25.0cm3 of solution B; (1 mark) ll. concentration in moles per litre of salt B in solution B; (1 mark) lll. relative molecular mass of salt B; (2 marks) 2 (a) You are provided with solid D. Carry out the following tests and write your observations and inferences in the spaces provided. (i) Place about one half of solid D in a test-tube and heat it strongly. Test any gases produced with both red and blue litmus papers. Observations (2 marks) Inferences (1 mark) (ii) Place the rest of solid D in a boiling tube. Add about 10cm3 of distilled Water. Shake well. To a 2cm3 portion of the solution, add about 1cm3 of hydrogen peroxide and shake well. To the resulting mixture, add aqueous sodium hydroxide dropwise until in excess. Observations (1 mark) Inferences(1 mark) (b) You are provided with solution E. Carry out the following tests and write your observations and inferences in the spaces provided. Divide solution E into two portions. (i) To one portion of solution E in a test-tube, add 3 drops of barium nitrate. Retain the mixture for use in test (ii) below. Observations (1 mark) Inferences (2 marks) (ii) To the mixture obtained in (i) above, add about 5 cm3 of 2M nitric (V) acid. Observations (1 mark) Inferences (1 mark) (iii) To portion two of solution E in a test-tube, add 2 drops of acidified potassium dichromate (VI) and warm the mixture. 3 You are provided with liquid F. Carry out the following tests and record your observations and inferences in the spaces provided. (a) Place five drops of liquid F on a clean dry watch glass and ignite it Observations(1 mark) Inferences(1 mark) (b) Place about 2cm3 of liquid F in a clean dry test tube, add all the sodium hydrogen carbonate provided. Observations (1 mark) Inference;(1 mark) (c) Place about 2cm3 of liquid F in a test-tube, add about 1cm3 of acidified potassium dichromate (VI) and warm the mixture. Observations (1 mark) Inferences(1 mark)  

Chemistry Paper 2 (233/2) 1 The flow chart below shows some of the processes involved in large scale production of sulphuric (VI) acid. Use it to answer the questions that follow. (a) Describe how oxygen is obtained from air on a large scale. (3 marks) (b) (i) Name substance A. (1 mark) (ii) Write an equation for the process that takes place in the absorption chamber. (1 mark) (c) Vanadium (V) oxide is a commonly used catalyst in the contact process. (i) Name another catalyst which can be used for this process. (1 mark) (ii) Give two reasons why vanadium (V) oxide is the commonly used catalyst. (2 marks) (d) State and explain the observations made when concentrated sulphuric (VI) acid is added to crystals of copper (II) sulphate in a beaker. (2 marks) (e) The reaction of concentrated sulphuric (V1) acid with sodium chloride produces hydrogen chloride gas. State the property of concentrated sulphuric (Vi) acid illustrated in this reaction. (1 mark) (f) Name four uses of sulphuric (VI) acid. (2 marks) 2 The set-up below was used by a student to investigate the products formed when aqueous copper (ll) chloride was electrolysed using carbon electrodes. (a) (i) Write the equation for the reaction that takes place at the cathode. (1 mark) (ii) Name and describe a chemical test for the product initially formed at the anode when a highly concentrated solution of copper (ll) chloride is electrolysed. (3 marks) (iii) How would the mass of the anode change if the carbon anode was replaced with copper metal? Explain. (2 marks) (b) 0.6 g of metal B Were deposited when a current of O.45A was passed through an electrolyte for 72 minutes. Determine the charge on the ion of metal B. (Relative atomic mass of B = 59, 1 Faraday = 96 500 coulombs) (3 marks) (c) The electrode potentials for cadmium and zinc are given below: Explain why it is not advisable to store a solution of cadmium nitrate in a container made of zinc. (2 arks) 3 (a) Ethanol can be manufactured from ethene and steam as shown in the equation below: Temperature and pressure will affect the position of equilibrium of the above reaction. Name the other factor that will affect the position of equilibrium of the above reaction. (1 mark) (b) The data in the table below was recorded when one mole of ethene was reacted with excess steam. The amount of ethanol in the equilibrium mixture was recorded under different conditions of temperature and pressure. Use the data to answer the questions that follow. (i) State whether the reaction between ethene and steam is exothermic or endothermic. Explain your answer. (3 marks) . (ii) State and explain one advantage and one disadvantage of using extremely high pressure in this reaction. I. Advantage (2 marks) II. Disadvantage (2 marks) (c) In an experiment to determine the rate of reaction between calcium carbonate and dilute hydrochloric acid, 2g of calcium carbonate were reacted with excess 2 M hydrochloric acid. The volume of carbon (IV) oxide evolved was recorded at regular intervals of one minute for six minutes. The results are shown in the table below. (i) Plot a graph of time in minutes on the horizontal axis against volume of carbon (IV) oxide on the vertical axis. (3 marks) (ii) Determine the rate of reaction at 4 minutes. (2 marks) 4 (a) When excess calcium metal was added to 50 cm3 of 2 M aqueous copper (II) nitrate in a beaker, a brown solid and bubbles of gas were observed. (i) Write two equations for the reactions which occurred in the beaker. (2 marks) (ii) Explain why it is not advisable to use sodium metal for this reaction. (2 marks) (b) Calculate the mass of calcium metal which reacted with copper (II) nitrate solution. (Relative atomic mass of Ca = 40) (2 marks) (c) The resulting mixture in (a) above was filtered and aqueous sodium hydroxide added to the filtrate dropwise until in excess. What observations were made?(1 mark) (d) (i) Starting with calcium oxide, describe how a solid sample of calcium carbonate can be prepared. (3 marks) (ii) Name one use of calcium carbonate. (1 mark) 5. (a) Other than their location in the atom, name two other differences between an electron and a proton. (2 marks) (b) The table below gives the number of electrons, protons and neutrons in particles A, B,C,D, E,F and G.   (i) Which particle is likely to be a halogen?(1 mark) (ii) What is the mass number of E?(1 mark) (iii) Write the formula of the compound formed when E combines with G.(1 mark) (iv) Name the type of bond formed in (m) above.(1 mark) (v) How does the radii of C and E compare? Give a reason.(2 marks) (vi) Draw a dot (.) and cross (X) diagram for the compound formed between A and F.(1 mark) (vii) Why would particle B not react with particle D?(1 mark) 6 (a) Study the flow chart below and answer the questions that follow. (i) I What observation will be made in Step I?(1 mark) II Describe a chemical test that can be carried out to show the identity of compound C.(2 marks) (ii) Give the names of the following:(2 marks) I E …………………………. II Substance D ……………… (iii) Give the formula of substance B.(1 mark) (iv) Name the type of reaction that occurs in:(1 mark) I Step (II) ………………………. II Step (IV) ………………………. (v) Give the reagent and conditions necessary for Step (2 marks)(VI). Reagent: ………………….. Conditions ……………… .. (b) (i) Name the following structure. (ii) Draw the structure of an isomer of pentene. (1 mark) 7 (a) What is meant by molar heat of combustion? (1 mark) (b) State the Hess’s Law. (1 mark) (c) Use the following standard enthalpies of combustion of graphite, hydrogen and enthalpy of formation of propane. (i) Write the equation for the formation of propane. (1 mark) (ii) Draw an energy cycle diagram that

Chemistry Paper 1 (233/1) 1 (a) What name is given to the process by which alcohol is formed from a carbohydrate? (1 mark) (b) Explain why the solubility of ethane in water is lower than that of ethanol. (2 marks) 2 Complete the nuclear equation below: (a) (c) Give one harmful effect of radioisotopes. (1 mark) 3 A mixture contains ammonium chloride, copper (II) oxide and sodium chloride. Describe how each of the substances can be obtained from the mixture. (3 marks) 4 The set-up below shows how nitrogen gas is prepared in the laboratory. (a) Describe how nitrogen gas is formed in the flask. (2 marks) (b) Nitrogen is inert. State one use of the gas based on this property. (1 mark) 5 The diagram below represents part of the periodic table. Use it to answer the questions that follow: (a) Write the electronic arrangement for the stable ion formed by W. (1 mark) (b) Write an equation for the reaction between V and Q. (1 mark) (c) How do the ionisation energies of the elements M and T compare? Explain. (1 mark) 6 A certain mass of gas occupies 0.15dm3 at 293 K and 98,648.5Pa. Calculate its volume at 101325 Pa and 273 K. (2 marks) 7 When lead(ii) nitrate is heated. one of the products is a brown gas. (a) Write the equation of the reaction that occurs. (1 mark) (b) If O.290dm3 of the brown gas was produced, calculate the mass of the lead(ii) nitrate that was heated. (R.F.M of lead (II) nitrate = 331; Molar gas volume = 24dm3). (2 marks) 8 (a) What is meant by a strong acid? (1 mark) (b) In an experiment, 40cm3 of 0.5M hydrochloric acid was reacted with excess sodium carbonate and the volume of carbon (IV) oxide produced recorded with time. In another experiment, the same volume and concentration of ethanoic acid was also reacted with excess sodium carbonate and the volume of carbon(iv) oxide produced recorded with time. On the grid below, sketch and label the curves if the volumes of carbon (IV) oxide were plotted against time. (2 marks) Volume of C02 cm3 9 State two reasons why hydrogen is not commonly used as a fuel. (2 marks) 10 During a class experiment, chlorine gas was bubbled into a solution of potassium iodide. (a) State the observations made. (1 mark) (b) Using an ionic equation, explain why the reaction is redox. (2 marks) 11 Exhaust fumes of some cars contain carbon (II) oxide and other gases. (a) Explain how carbon (II) oxide is formed in the internal combustion engines. (1 mark) (b) Name two gases other than carbon (II) oxide that are contained in exhaust fumes and are pollutants. (2 marks) 12 Sodium hydroxide can be prepared by the following methods; I and II. (a) Name one precaution that needs to be taken in method I. (1 mark) (b) Give the name of process A. (1 mark) (c) Give one use of sodium hydroxide. ( 1 mark) 13 Distinguish between the terms deliquescent and efflorescent as used in chemistry. (2 marks) 14 Two organic compounds P and Q clecolourise acidified potassium manganate (VII) solution; but only P reacts with sodium metal to give a colourless gas. Which homologous series does compound P belong? Give a reason. (2 marks) 15 Soap dissolves in water according to the equation below; (a) Write the formula of the scum formed when soap is used in hard water. (1 mark) (b) Write the ionic equation for the reaction that occurs when sodium carbonate is used to remove hardness in water. (1 mark) 16 Ethanoic acid and ethanol react as shown in the equation below: Other than warming, how would the state of equilibrium be established within a short time? (1 mark) 17 The set up below was used to prepare a gas and study some of its properties. Study it and answer the questions that follow: (a) State and explain the observations made in the: (i) tube labelled A; (1 mark) (ii) beaker labelled B. (1 mark) (b) State one precaution that should be taken when carrying out this experiment. (1 mark) 18 Under certain conditions, chlorine gas reacts with sodium hydroxide to form sodium hypochloxite. (a) Name the conditions under which sodium hydroxide reacts with chlorine to form sodium hypochlorite. (1 mark) (b) State two uses of sodium hypochlorite. (2 marks) 19 50kg of ammonium sulphate (NH4)2 SO4 and 30kg of urea :CO(NH2)2 fertilizers were applied in two equal sizes of plots A and B to enrich their nitrogen content. Show by working, which plot was more enriched with nitrogen. (N = 14; S = 32; O = 16; C = 12; H = 1) (3 marks) 20 Describe how the PH of anti-acid (Actal) powder can be determined in the laboratory. (2 marks) 21 Graphite is one of the allotropes of carbon. (a) Name one other element which exhibits allotropy. (1 mark) 22 The table below gives some properties of three elements in group (VII) of the periodic table. Study it and answer the questions that follow: (a) Which element is in liquid fonn at room temperature? Give a reason. (1 mark) (b) Explain why the boiling point of iodine is much higher than that of chlorine. (2 marks) 23 The thermalchemical reaction between carbon and sulphur is as shown by the equation below: On the grid below, sketch and label the energy level diagram for the reaction. (2 marks) 24 The table below gives the number of electrons, protons and neutrons in substances X, Y and Z. study it and answer the questions below (a) Which letter represents an ion? (1 mark) (b) Which of the substances are isotopes? Give a reason. (2 marks) 25 (a) State the Gay Lussac’s Law. (1 mark) (b) 1Ocm3 of a gaseous hydrocarbon, C2HX required 30cm3 of oxygen for complete combustion. If steam and 20cm3 of carbon (iv) oxide were produced, what is the value of X? (2 marks) 26 The

Chemistry Paper 3 (233/3) 1 You are provided with:   solution A’ aqueous copper (H) sulphate;  solid B, iron powder;  0.02 M acidified potassium manganate (VII), solution C.You are required to determine the molar heat of displacement of copper by iron. Procedure I Using a burette, place 50.0 cm’ of solution A in a 100 ml beaker. Measure the temperature of the solution and record it in table 1 below. Add all of solid B provided at once and start a‘ stop watch. Stir the mixture thoroughly with the thennometer and record the temperature of the mixture after every one minute in the table. Retain the mixture for use in procedure II below.   (a) (i) Plot a graph of temperature (vertical axis) against time in the grid provided. (3 marks) (ii) From the graph, determine the; (I) highest change in temperature, AT; (1 mark) (II) time taken for reaction to be completed. (1mark) (iii) Calculate the heat change for the reaction. (Specific heat capacity of solution is 4.2 Jg” K”; Density of the solution is l gem”). (2 marks) Procedure II Carefully decant the mixture obtained in procedure I into a 250 ml volumetric flask. Add about 10 cm’ of distilled water to the residue in the 100 ml beaker. Shake well, allow the mixture to settle and carefully decant into the volumetric flask. Immediately, add about 50 cm‘ of 2 M sulphuric (VI) acid to the mixture in the volumetric flask. Add more distilled water to make 250.0 cm‘ of solution. Label this as solution D. Fill a burette with solution C. Using a pipette and a pipette filler, place 25.0 cm’ of solution D into a 250 ml conical flask. Titrate solution D against solution C until the first permanent pink colour is obtained. Record your results in table 2 below. Repeat the titration two more times and complete the table. Retain the remaining solution C for use in question 3. TABLE II (a) Determine the average volume of solution C used. (1% mark) (b) Calculate the number of moles of: (i) aqueous potassium manganate (VII) used; (1 mark) (ii) iron (II) ions in 25 .0 cm3 of solution D. (1 mole of MnOZ reacts with 5 moles of Fe“). (1 mark (iii) iron(II) ions in 250 cm‘ of solution D. (1 mark) (c) Calculate the molar heat of displacement of copper by iron. (2 marks) 2.You are provided with solid E. Carry out the following tests and write your observations and inferences in the spaces provided. (a) Place all of solid E in a boiling tube. Add about 10 cm’ of distilled water and shake thoroughly. Filter the mixture into another boiling tube. Retain the filtrate for use in test 2 (b) below. Dry the residue using pieces of filter papers. (i) Transfer about half of the dry residue into a dry test-tube. Heat the residue strongly and test any gas produced using a burning splint. ii) Place the rest of the residue in a dry test—tube. Add 4 cm’ of 2M hydrochloric acid. Retain the mixture for test (m) below. iii) To 2 cm-‘ of the solution obtained in (ii) above, add 6 cm-‘ of aqueous ammonia dropwise. (b) (i) To 2 cm-‘ of the filtrate obtained in (a) above, add about 3 cm3 of aqueous ammonia (Excess). ii) To 2 cm’ of the filtrate, add about 2 cm’ of 2M hydrochloric acid. iii) T0 2 cm-‘ of the filtrate, add one or two drops of barium nitrate solution. 3. You are provided with solid G. Carry out the tests in (a) and (b) and write your observations and inferences in the spaces provided. Describe the method used in part (c). (a) Place about one third of solid G on a metallic spatula and bum it in a Bunsen burner flame. (b) Dissolve all of the remaining solid G in about 10 cm’ of distilled water in a boiling tube. Use the solution for tests . (i) Place 2 cm-‘ of the solution in a test-tube and add 2 drops of acidified potassium manganate (VII); solution C.   ) (ii) To 2 cm‘ of the solution, add all of solid sodium hydrogen carbonate provided. (c) Determine the pH of the solution obtained in (b) above.