1 Explain how the hotness of a Bunsen burner flame can be increased. (1 mark)
2 When dilute hydrochloric acid was reacted with solid B, a colourless gas which extinguished a buming splint was produced. When an aqueous solution of solid B was tested with a blue litmus paper, the paper turned red/ pink.
(a) Identify the anion present in solid B. (1 mark)
(b) Write an ionic equation for the reaction between solid B and dilute hydrochloric acid. (1 mark)
3 Dry ammonia gas was passed over heated lead (II) oxide and the products passed over anhydrous copper (II) sulphate as shown in the diagram below.
State:
(a) two observations made in the combustion tube. (2 marks)
(b) the property of ammonia gas shown in this experiment. (1 mark)
4 Starting with zinc sulphate solution, describe how a sample of Zinc oxide can be obtained. (3 marks)
5 Explain how conduction of electricity takes place in the following:
(a) iron metal; (1 mark)
(b) molten lead (ll) iodide. (1 mark)
6 100 cm3 of a sample of ethane gas diffuses through a porous pot in 100 seconds. What is the molecular mass of gas Q if 100 cm} of the gas diffuses through the same porous pot in l2l seconds under the same conditions?
(C = 12.0, H = 1.0) (3 marks)
7 (a) Draw and name the isomers of butyne. (2 marks)
13 100 cm3 of 0.05 M sulphuric (VI) acid were placed in a flask and a small quantity of anhydrous sodium carbonate added. The mixture was boiled to expel all the carbon (IV) oxide. 25 cmi of the resulting solution required 18 cm3 of 0.l M sodium hydroxide solution to neutralise it. Calculate the mass of sodium carbonate added. (Na : 23.0; O : 16.0; C = 12.0) (3 marks)
14 When 20 cm3 of l M sodium hydroxide was mixed with 20 cm3 of 1 M hydrochloric acid, the temperature rose by 6.7 “C. Assuming the density of the solution is l g/cm3 and the specific heat capacity of the solution is 4.2 J g” k”;
(a) calculate the molar heat of neutralisation; (2 marks)
(b) when the experiment was repeated with 1 M ethanoic acid, the temperature change was found to be lower than that with 1 M hydrochloric acid. Explain. (1 mark)
15 Study the set-up below and answer the questions that follow.
(ii) water level in the measuring cylinder after four days. (1 mark)
(b) What would be the effect of using steel wool moistened with salty water? (1 mark)
17 In an experiment on rates of reaction, potassium carbonate was reacted with dilute sulphuric
(VI) acid.
(a) What would be the effect of an increase in the concentration of the acid on the rate of the reaction? (1 mark)
(b) Explain Why the rate of reaction is found to increase with temperature. (2 marks) 18 Use the part of the periodic table given below to answer the questions that follow.
(Letters are not the actual symbols of the elements).
24 (a) A student electrolysed dilute sodium chloride solution using inert carbon electrodes. Name the products at:
(i) anode;
(ii) cathode.
(2 marks) (b) If the experiment was repeated using concentrated sodium chloride instead of dilute sodium chloride solution, Write the half equation at the anode. (1 mark)
25 An organic compound had the following composition 37.21% carbon, 7.75% hydrogen and the rest chlorine. Detemiine the molecular formula of the compound, given that the molecular mass of the compound is 65. (C : 12.0; H : 1.0; Cl : 35.5). (3 marks)
26 Cotton is a natural polymer. State one advantage and one disadvantage of this polymer. (2 marks)
Advantage: …………………………………………….. ..
Disadvantage: …………………………………………… ..
27 (a) Name a suitable solvent for extracting an indicator from flowers; (1 mark)
(b) Give a reason Why the solvent named in (a) above is used. (1 mark)
28 A student used the set up below to prepare a sample of nitrogen gas.
(ii) When the bleaching powder is added to water during washing, a lot of soap is used. Explain. (1 mark)
2 (a) The grid below represents part of the periodic table. Study it and answer the questions that follow. The letters are not the actual symbols of the elements.
(ii) Select an element that can form an ion with a charge of 3 . (1 mark)
(iii) Select an alkaline earth metal. (1 mark)
(iv) Which group l element has the highest first ionization energy? Explain. (2 marks)
(v) Element A combines with chlorine to form a chloride of A. State the most likely pH value of a solution of a chloride of A. Explain. (2 marks)
(b) (i) Explain why molten calcium chloride and magnesium chloride conduct electricity While carbon tetrachloride and silicon tetrachloride do not. (2 marks)
(ii) Under the same conditions, gaseous neon was found to diffuse faster than gaseous fluorine. Explain this observation. (F = 19.0; Ne = 20.0) (2 marks)
3 (a) Draw the structures of the following:
(i) Butan- l -ol (1 mark)
(ii) Hexanoic acid. (1 mark)
(b) Study the flow chart below and answer the questions that follow.
(ii) State one reagent that can be used to carry out process S. (1 mark)
(m) Identify gases: (2 marks)
P: ………………………………… ..
T: ………………………………… ..
(iv) How is sodium hydroxide kept dry during the reaction? (1 mark)
(v) Give one commercial use of process R. (1 mark)
(c) When one mole of ethanol is completely burnt in air, l370kj of heat energy is released. Given that 1 litre of ethanol is 780g, calculate the amount of heat energy released when l litre of ethanol is completely burnt. (3 marks)
(C = 12.0; H= 1.0; O = 16.0)
(d) State two uses of ethanol other than as an alcoholic drink. (2 marks) 4 (a) Other than temperature, state two factors that determine the rate of a chemical reaction. (1 mark)
(b) A solution of hydrogen peroxide was allowed to decompose and the oxygen gas given off collected. After 5 minutes, substance G was added to the solution of hydrogen peroxide. The total volume of oxygen evolved was plotted against time as shown in the graph below.
(ii) Write an ionic equation for the reaction in Step II. (1 mark)
(iii) What observations would be made in Step V? Give a reason. (2 marks)
(iv) Explain why the total volume of hydrogen gas produced in step 1 was found to be very low although calcium and solution D were in excess. (2 marks)
(v) State one use of substance E. (1 mark)
(b) Starting with solid sodium chloride, describe how a pure sample of lead (ll) chloride can be prepared in the laboratory. (3 marks)
(c) (i) State a property of anhydrous calcium chloride which makes it suitable for use as a drying agent for chlorine gas. (1 mark)
(ii) Name another substance that can be used to dry chlorine gas. (1 mark)
6. The diagram below represents a set up of an electrolyte cell that can be used in the production of aluminium
(b) Write the equation for the reaction at the anode (1 mark)
(c)Give a reason why the electrolyte process is not carried out below 950°C (1 mark)
(d) Give a reason why the production of aluminium is not carried out using reduction process (1 mark)
(e) Give two reasons why only the aluminium ions are discharged (2 marks)
(f) State two properties of duralumin that makes it suitable for use in aircraft industry (g)Name two environmental effects caused by extraction of aluminum (2 marks)
7. (a) Dissolving of potassium nitrate tn water rs an endothermic process Explain the effect of increase in temperature on the solubility of potassium nitrate (b) The table below shows the solubility of potassium sulphate and potassium chlorate (V) at different temperatures.
(ii) A solution of potassium sulphate contains 20g of the salt dissolved in 100g of water at 100°C. This solution is allowed to cool to 25°C. I At what temperature will crystals first appear? (1 mark)
ll What mass of crystals will be present at 25“C? (1 mark)
(111) Which of the two salts is more soluble at 30°C? (1 mark)
(iv) Determine the concentration of potassium sulphate in moles per litre when the solubility of the two salts a.re the same (K = 39.0, O = l6.0; S = 32.0). (3 marks) (v) 100g of water at 100°C contains 19g of potassium sulphate and 19g of potassium chlorate (V). Describe how a solid sample of potassium sulphate at 60 C can be obtained. (2 marks)
3.6.3 Chemistry Paper 3 (233/3)
1 You are provided with:
– solution J containing copper (ll) ions.
solution K, 0.1 M sodium thiosulphate.
aqueous potassium iodide, solution L.
solution N, sodium hydroxide.
starch indicator, solution M.
You are required to determine the:
– concentration of copper (ll) ions in solution J;
– enthalpy change of reaction between copper (ll) ions and hydroxide ions.
PROCEDURE 1
(a) Using a pipette and pipette filler, place 25.0 cm-‘ of solution J in a 250 ml volumetric flask. Add distilled water to make up to the mark. Label this as solution J2. Retain solution J for use in procedure II.
Place solution K in a burette. Using a clean pipette and pipette filler, place 25.0 cm3 of solution J2 in a 250 ml conical flask. Add 10 cm3 of potassium iodide, solution L.
Shake well, then add 2 cm3 of starch indicator, solution M. Titrate until a blue-black colour appears and continue titrating until the blue-black colour just disappears.
Record your readings in Table 1 below.
(c) Repeat step (b) two more times and complete Table 1.
(iii) concentration in moles per litre of copper (ll) ions in solution J given that the number of moles of copper (ll) ions in 25.0 cm} of solution J2 are the same as the moles of sodium thiosulphate used. (2 marks)
PROCEDURE 11
(a) Using a clean burette, place 5.0 cm3 of solution N into each of six (6) test-tubes. (b) Using a 100 ml measuring cylinder, place 20 cm3 of solution J in a 100 ml plastic beaker. Measure the temperature of solution J and record it in Table 2 below.
(c) To solution J in the beaker, add sodium hydroxide, solution N from one of the test-tubes. Stir the mixture with the thermometer and record in Table 2, the maximum temperature reached. Continue with step (d) IMMEDIATELY.
(d)Add the sodium hydroxide, solution N from another test-tube to the mixture obtained in (c) above, stir and record the maximum temperature reached in Table 2. Continue adding the sodium hydroxide, solution N from each of the other four test-tubes, stirring the mixture and recording the maximum temperature each time and complete Table 2.
I volume of sodium hydroxide, solution N that reacted completely with 20 cm3 of solution J; (2 marks)
II temperature change, AT, for the reaction; (1 mark)
(iii) enthalpy change of the reaction per mole of copper (ll)ions. (3 marks)
(Heat capacity I 4.2 J g”k”, density of the mixture I 1.0 g cm’3). 2 You are provided With substance P. Can”y out the tests below and Write your observations and inferences in the spaces provided.
(a) Describe the appearance of substance P. (1 mark)
(b) Place about one-third of substance P in a dry test-tube and heat it strongly.
(ii) To sterise equipment/treatment of cancer/radio active Na for disorders in blood circulation/Barium meal for ulcers/detect fractures in bones. (l)
9. The molecules of ethanoic acid interact through strong hydrogen bonding (1) forming a dimer while molecules of pentane have weak van der waals forces. (1) NB/ Ethanoic acid has hydrogen bonds while pentane does not have.
(b) The solvent dissolves the organic compound indicator present in the flowers / it is an organic solvent. (1)
28. (a) It absorbs carbon (IV) oxide present in the air. (1)
(b) Copper /Cuts) (1)
(c) It has rare noble gases which have not been removed / Argon. (1)
29. (a) A radical is a compound formed when elements combine to form ions / free unstable atoms or molecules / a group of free unstable atoms exist in a compound / group of atoms with a common charge. (1)
