KCSE Past Papers 2019 Chemistry Paper 2 (233/2)

KCSE Past Papers 2019 Chemistry paper 2(233/2)

Kenya Certificate of Secondary Education

2019 Chemistry paper 2

1. (a) Alkanes are said to be saturated hydrocarbons.

(i) What is meant by saturatcd hydrocarbons. (1 mark)

(ii) Draw the strucuire of the third member of the alkane homologous series and name it. (2 marks)

(b) When the alkane, hexane, is heated to high temperature, one of the products is ethene.

(i) Write the equation for the reaction. (1 marks)

(ii) Name the process described in (b). (1 marks)

(c) Study the flow chart in Figure 1 and answer the questions that follow.

(i) Identify A. (1 marks)

(ii) State one physical property of B. (1 marks)

(iii) Draw the structure of D. (1 marks)

(iv) Give a reason why D pollutes the environment.(1 marks)

(v) Write an equation for the formation of F.(1 marks)

(d) Describe an experiment which can be used to distinguish butene from butanol. (2 marks)

2. (a) Zinc occurs mainly as zinc blende. Name one other ore from Which zinc can be extracted.(1 marks)

(b) The flow chart in Figure 2 shows the various stages in the extractİoil of zinc metal. Study it and answer the questions that follow.

(i) Write an equation for the reaction which occurs in the roasting chamber. (1 mark)

(ii) Describe the process that takes place in the blast furnace. (3 mark)

(iii) Explain why molten lead is added to the condenser. (1 mark)

(iV) State two uses of zinc.(1 mark)

(v) Give one reason why the extraction of zinc causes pollution to the environment.(1 mark)

(c) Explain the observations made when zinc metal is added to hot sodium hydroxide. (2 marks)

3. Figure 3 is a flow chart that shows the proccss that occurs in the manufacture of nitric(v)acid

(a) Name substance P, Q, R and S. P……………………… (1 marks)

Q………………………… (1 marks)

R…………………………..(1 marks)

S…………………………….(1 marks)

(b) To obtain substance R, ammonia is heated at 900 °C in the presence of air and a catalyst.The product is then cooled in air.

(i) Name the catalyst for the reaction. (1 marks)

(ii) Write the equations for the two reactions described in (b). (2 marks)

(iii) Other than nitric(V) acid, name another product that is formed. (1 mark)

(c) When ammonia is reacted with nitric(V) acid, it produces a nitrogenous fertiliser.

(i) Explain why fertilisers play a major role in food production. (2 marks)

(ii) State two problems associated with the use of nitrogenous fertilisers. (2 marks)

4. (a) Explain the following observations:

(i) The colour of aqueous copper(ii) sulphate fades when a piece of magnesium metal is droppcd into the solution. (2 marks)

(ii) A piece of iron bar is coated with a brown substance when left in the open on a rainy day. (2 marks)

(b) A sample of water is suspected to contain aluminium ions (AI3+) .

Describe a laboratory experiment that can be carried out to show that AI3+ ions are present in the water sample. (3 marks)

(c) In an experiment to determine the number of moles of water of crystallisation of a hydrated compound Na2SO4.XHsO,5g of the compound were heated strongly to a constant mass.

(i) Explain how a constant mass was obtained. (2 marks)

(ii) During the experiment, the mass of the residue was found to be 2.205 g.

Determine the number of moles of water of crystallisation in the compound. (Na = 23.0 ; O = 16.0 ; S = 32.0 ; H = 1.0) (3 marks)

5. (a) What is meant by a molar heat of neutralisation? (1 marks)

(b) In an experiment to determine the molar heat of neutralisation, 50 cm3 of IM hydrochloric acid was neutralised by adding 10 cm3 Onions Of dilute sodium hydroxide.

During the experiment, the data in Table 1 was obtained.

(i) Write the equation for the reaction in this experiment. (1 mark)

(ii) On the grid provided, plot a graph of temperature (Y-axis) against volume of sodium hydroxide (X-axis) added. (3 marks)

(iii) Determine from the graph the:

I. volume of sodium hydroxide which completely neutralises 50 cm3 of lM hydrochloric acid. (1 mark)

11. change in temperature, AT, when complete neutralisation occurred. (1 mark)

(IV) Calculate:

I. The heat change, dH when complete neutralisation occurred. (Specific heat capacity = 4.2 Jg-1 K-1 density of solution 1.0 gcm-3)(2 marks)

(v) How would the value of molar heat differ if 50 cm3 of lM ethanoic acid was used instead of IM hydrochloric acid? Give a reason. (2 marks)

6. (a) What is meant by standard electrode potential of an element (1 mark)

(b) Use the standard electrode potcntials given below to answer the questions that follow.

(i) State whether acidified MnO4 can oxidise M2+. Give a reason. (2 marks)

(ii) Select two half-cells which when combined will give the highest e.m.f. (1 mark)

(iii) Write the cell representation for the cell formed in b (ii). (1 mark)

(iv) Calculate the Eθ value for the cell formed in b (iii). (1 mark)

(c) A mass of 1.24g of a divalent metal was deposited when a current of 6A was passed through a solution of a metal sulphate for 12 minutes.Determine the relative atomic mass of the metal( Faraday = 96,500 C mol -1 (3 mark)

(d) State two application s of electrolysis. (I mark)

7. (a) What is meant by rate of reaction (1 mark)

(b) In the space provided, Sketch the diagram of a set-up that Can be used to determine the rate of reaction between manganese(IV) oxide and hydrogen peroxide. (3 marks)

(c) A student placed a small amount of liquid bromine at the bottom of a sealed gas jar of air as shown in Figure 4.

(i) Describe what will be observed: (1 mark)

I. After two minutes………………………….

II. After 30 minutes ……………………..

(ii) Use the Kinetic theory to explain the observations: (2 marks)

I. After two minutes………………………….

II. After 30 minutes ……………………..

(d) Some plants have seeds that contain vegetable oil.

(i) Describe how the oil can be obtained from the seeds. (3 marks)

(ii) Explain how it could be confirmed that the liquid obtained from the seeds is oil. (1 mark)

 

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