CHEMISTRY PAPER 1 2006

QUESTIONS

1. (a) What is meant by isomerism? (1mark)

(b) Draw and name two isomers of butane. (2 marks)

chem 015

2. The diagram below represent a set-up that was used to show that part of air is used during burning.

a) Given that phosphorus used was was in excess, draw a diagram of the set-up at the end of the experiment (when there was no further observable change). (1mk)

b) Suggest one modification that should be made on the apparatus if the percentage of the air used is to be determined. (1mk)

3. 60cm3 of oxygen gas diffused through a porous partition in 50 seconds. How long would it take 60cm3 of sulphur (IV) oxide gas to diffuse through the same partition under the same conditions? (S= 32.0, 0 = 16.0) (3marks)

4. a) Complete the nuclear equation below.

(1mark)

b) 37                    37

 

A…………………….B

 

18                        17

 

(b) State one

(i) Use of radioisotopes in agriculture (1mark)

(ii) Danger associated with exposure of human beings to radioisotopes

(1 mark)

5. The atomic numbers of elements C and D are 19 and 9 respectively. State and explain the electrical conductivity of the compound CD in:

(a) Solid state (1 ½ marks)

(b) aqueous state. (1 ½ marks)

6. In an experiment to study the properties of concentrated sulphuric acid, a mixture of the acid and wood charcoal was heated in a boiling tube.

(a) write the equation of the reaction that took place in the boiling tube.(1mark)

(b) Using oxidation numbers, show that reduction and oxidation reactions took place in the boiling tube (2 mark)

7. A group of compounds called chlorofluorocarbons have a wide range of uses but they also have harmful effects on the environment.

State one:

a) Use of chlorofluorocarbons (1 mark)

b) Harmful effect of chlorofluorocarbons on the environments. (1 mark)

8. when 94.5g of hydrated barium hydroxide, ba(OH)2. nH2O were heated to constant mass, 51.3g of anhydrous barium hydroxide were obtained. Determine the empirical formula of the hydrated barium hydroxide. (3 marks)

9. at 200C, NO2 and N2 O4 gases exist in equilibrium as shown in the equation below

2 NO2(g) N2O4(g); H = -ve

Brown pale yellow

State and explain the observation that would be made when;

a) A syringe containing the mixture at 200C is immersed in ice-cold water

(1 ½ mks)

b) the volume of the gaseous mixture in a syringe is reduced. (1 ½ mks)

10 Name the process which takes place when:

a) Solid carbon (IV) oxide (dry ice) changes directly into gas (1 mark)

b) A red litmus paper turns white when dropped into chlorine water. (1 mark)

c) Propane gas molecules are converted into a giant molecule (1 mark)

11. a) water from a town in Kenya is suspected to contain chloride ions but not sulphate ions.

Describe how the presence of the chloride ions in the water can be shown. (1 mk)

b) State one advantage of drinking hard water rather than soft water. (1 mk)

12. The table below shows the relative atomic masses and the percentage abundance of the isotopes L1 of element L.

chem 016 13. The diagram below represents the set-up that was used to prepare and collect hydrogen chloride gas in the laboratory.

a) State the purpose of concentrated sulphuric acid in the wash bottle. (1 mark)

b) Write an equation for the reaction between dry hydrogen chloride gas and

heated iron (1 mark)

c) Hydrogen chloride gas is dissolved in water to make hydrochloric acid. State one use of hydrochloric acid.

14. Below is a list of oxides.

MgO, N2O, K2O, CaO, and Al2O3.

Select:

a) A neutral oxide (1 mk)

b) A highly water soluble basic oxide (1 mark)

c) An oxide which can react with both sodium hydroxide solution and dilute

hydrochloric acid. (1 mk)

15. Study the standard reduction potential given and answer the questions that follow.

(The letters are not the actual symbols of the elements).

Eø (volts)

M2+(aq) + 2e → M(s) -0.76

N2+(aq) + 2e → N(s) -2.37

P+(aq) + e → P(s) +0.80

Q2+(aq) +2e → Q(s): -0.14

a) The standard reduction potential for Fe 2+(aq) is -0.44 volts. Select the element which would best protect iron from rusting. (1 mark)

b) Calculate the E ø value for the cell represented as M(s) / M2+ (aq) // p+(aq) /P(s).

(2mks)

16 When hydrogen sulphide gas was bubbled into an aqueous solution of iron (III) chloride, a yellow precipitate was deposited. (1mark)

a) The standard reduction potential for Fe2+ (aq) is -0.44 volts. Select the element which would best protect iron from rusting. (1 mark)

b) Write an equation for the reaction that took place. (1 mark)

c) What type of reaction was undergone by hydrogen by hydrogen sulphide in this reaction? (1mark)

17. The first step in the industrial manufacture of nitric acid is the catalytic oxidation of ammonia gas.

(a) What is the name of the catalyst used? (1 mk)

(b) Write the equation for the catalytic oxidation of ammonia gas. (1mk)

(c) Nitric acid is used to make ammonium nitrate, state two uses of ammonium

nitrate. (1 mark)

18. Study the diagram below and answer the question that follows.

chem 017

Describe one chemical test that can be carried out to identify substance s. (2 marks)

19. a) starting from solid magnesium hydroxide. (1mark)

b) Give one use of magnesium hydroxide. (1 mark)

20. a) Distinguish between a covalent bond and a co-ordinate bond ( 2 marks)

b) Draw a diagram to show bonding in an ammonium ion. (1mark)

21. (a) Explain why the metals magnesium and aluminium are good conductors of electricity. (1 mark)

b) Other than cost, give two reasons why aluminium is used for making

electric cables while magnesium is not (2mks)

22. The diagram below represents part of a set – up used to prepare and collect gas T.

chem 018

a) Name two reagents that are reacted to produce both carbon (IV) oxide and carbon(II) oxide.(1mk)

b) Write the equation for the reaction which takes place in the wash bottles.(1mk)

c) Give a reason why carbon(II) oxide is not easily detected.(1mk)

23. Explain why the boiling point of ethanol is higher than that of hexane.

(Relative molecular mass of ethanol is46 while that of hexane is 86)

24. a) Complete the table below to show the colour of the given indicator in

Indicator Colour in
Acid solution Basic solution
Methyl orange ……………. Yellow
Phenolpthalein Colourless ………………

b) How does the PH value of 0.1 M potassium hydroxide solution compare with that of 0.1M aqueous ammonia? Explain. (2mks)

25. Study the properties of substances V1 to V4 in the table below and answer

the questions that follow.

Substance Solubility in water Solubility Melting Point(oC) Boiling point(oC)
V1 Insoluble Soluble -30 250
V2 Insoluble Insoluble 1535 3000
V3 Insoluble Soluble 16.8 44.8
V4 Insoluble Soluble 75 320

a) Which of the substances are liquids at 240C?

b) Describe how a mixture containing V2 and V4 can be separed (2mks)

26. The graph below shows a curve obtained when water at 20oC was heated for 15 minutes.

chem 019

a) What happens to the water molecules between points W and x? (1mk)

b) In which part of the curve does a change of state occur? (1mk)

c) Explain why the temperature does not rise between points X and Y. (1mk)

chem 020 27. Study the flow chart below and answer the questions that follow.

a) Name reagent z.

b) Describe the process which takes place in step 2.(1mk)

c) Identify the white solid. (1mk)

chem 021 28. Study the diagram below and answer the questions that follow.

a) What do H1 and H2 represent? (2mks)

b) Write an expression to show the relationship between H1,H2 and H3.(1mk)

CHEMISTRY PAPER 2 (233/2) 2006

QUESTIONS

1. a) What is an electrolyte? (1mk)

b) State how the following substances conduct electricity.

i) Molten calcium chloride (1mk)

ii) Graphite. (1mks)

chem 022 c) The diagram below shows a set up that was used to electrolyse aqueous magnesium sulphate.

i) On the diagram above, using an arrow, show the direction

of flow of electrons. (1mk)

ii) Identify the syringe in which hydrogen gas would be collected. Explain (1mk)

d) Explain why the concentration of magnesium sulphate was found to have

increased at the end of the experiment. (2mks)

e) During the electrolysis, a current of 0.72A was passed through the electrolyte for 15 munites.Calculate the volume of gas produced at the anode.(1 Faraday = 96 500 coulombs; molar gas volume is 24000cm3 at room temperature). (4mks)

2. a) In an experiment to determine the molar heat of reaction when magnesium displaces copper ,0.15g of magnesium powder were added to 25.0cm3 of 2.0M copper (II) chloride solution. The temperature of copper (II) chloride solution was 25oC.While that of the mixture was 43oC.

i) Other than increase in temperature, state and explain the observations which were made during the reaction.(3mks)

ii) Calculate the heat change during the reaction (specific heat capacity of the solution = 4.2jg-1k-1and the density of the solution = 1g/cm3(2mks)

iii) Determine the molar heat of displacement of copper by magnesium.(Mg=24.0).

iv) Write the ionic equation for the reaction.(1mk)

v) Sketch an energy level diagram for the reaction.(2mks)

b) Use the reduction potentials given below to explain why a solution

containing copper ions should not be stored in a container made of zinc.

Zn2+(aq) + 2e Zn(s); Eø = -0.76v

Cu2+(aq) + 2e Cu(s); Eø = +0.34v (2mks)

3. a) Distinguish between isotopes and allotropes. (2mks)

b) The chart below is part of the periodic table. Study it and answer the questions that follow.(The letters are not the actual symbols of the elements).

i) Select the element in period three which has the shortest atomic radius. Give a reason for you answer. (2mks)

ii) Element F has the electronic structure, 2.8.18.4 on the chart above, indicate the position of element F. (1mks)

iii) State one use of the elements of which E is a member. (1mk)

iv) Write an equation to show the action of heat on the nitrate of element C.

(1mks)

c) When 3 litres of chlorine gas were completely reacted with element D, 11.875g

of the product were formed.Dertermine the relative atomic mass of element D.

(Atomic mass of chlorine = 35.5; molar gas volume = 24litres).(3mks)

4. a) The diagram below shows some processes that take place during

chem 023 the industrial manufacture of sulphuric acid.

(i) Write the equation for the reaction in which sulphur dioxide gas is produced. (1mk)

(ii) Why is it necessary to keep the gases pure and dry ? (1mk)

(iii) Describe the process that takes place in chamber G. (1mk)

(iv) Name the gases that escape into the environment. (1mk)

(v) State and explain the harmful effect on the environment of one of the gases named in (iv) above (1mk)

(vi) Give one reason why it is necessary to use a pressure of 2-3 atmoshperes and not more. (1mk)

b) (i) Complete the table below to show the observations made when

concentrated sulphuric acid is added to the substances shown. (2mks)

 

Substance Observation
Iron fillings
Crystals of white sugar

(ii) Give reasons for the observations made using:

I iron fillings (1mk)

II Crystals of white sugar. (1mk)

(c) Name one fertilizer made from sulphuric acid. (1mk)

(d) Suggest a reason why BaSO4(apigment made from sulphuric acid) would be suitable in making paint for cars. (1mk)

5. a) What name is given to a compound that contains carbon and hydrogen only? ( ½)

b) Hexane is a compound containing carbon and hydrogen.

(i) What method is used to obtain hexane from crude oil? (1mk)

(ii) State one use of hexane (1mk)

c) Study the flow chart below and answer the questions that follow.

chem 025

(i) Identify reagent L. (1mk)

(ii) Name the catalyst used in step 5. (1mk)

(iii) Draw the structural formula of gas J. (1mk)

(iv) What name is given to the process that takes place in step 5? (½mk)

d) (i) write the equation for the reaction between aqueous sodium hydroxide and aqueous ethanoic acid. (1mk)

(ii) Explain why the reaction between 1g of sodium carbonate and 2M hydrochloric acid is faster than the reaction between 1g of sodium carbonate and 2M ethanoic acid. (1mks)

6. The extraction of iron from its ores takes place in the blast furnace. Study it and answer

chem 026 the questions that follow.

a) Name

(i) One of the substances in the slag (1mk)

(ii) Another iron ore material used in the blast furnance. (1mk)

(iii) One gas which is recycled. (1mk)

b) Describe the process which leacd to the formation of iron in the blast furnace

c) State the purpose of limestone in the blast furnace. (3mks)

d) Give a reason why the melting point of the iron obtained from the blast furnace is 12000 C while tat of pure iron is 15350C (1mk)

(e) State two uses of steel (2mks)

7. The table below shows the volumes of nitrogen dioxide gas produced when different volume of IM nitric acid were each reacted with 2.07 g of lead at room temperature.

Volume of 1 M nitric acid (cm3) Volume of nitrogen dioxide gas (cm3)
5 60
15 180
25 300
35 420
45 480
55 480

a) Give a reason why nitric acid is not used to prepare hydrogen gas. (1mk)

b) Explain how the rate of the reaction between lead and nitric acid would be affected if the temperature of the reaction mixture was raised. (2mks)

c) On the grid provided below, plot a graph of the volume of the gas produced (Vertical axis) against volume of acid. (3 marks)

d) Using the graph, determine the volume of:

i) Nitrogen dioxide produced when 30cm3 of 1 M nitric acid were reacted with 2.07 g of lead (1mrk)

ii) 1M nitric acid which would react completely with 2.07g of lead. (1mk)

e) Using the answer in d(i) above, determine:

i) The volume of 1M nitric acid that would react completely with one mole of lead (pb=207) (2mks)

ii) The volume of nitrogen dioxide gas produced when one mole of lead reacts with excess 1 M nitric room temperature. (1mk)

f) Calculate the number of moles of:

i) 1M nitric acid that reacted with one mole of lead (1mk)

ii) nitrogen dioxide produced when one mole of lead were reacted with excess nitric acid. (Molar gas volume of 2400cm3) (1mk)

g) Using the answers obtained in f (i) and (ii) above, write the equation for the reaction between lead and nitric acid given that one mole of lead nitrate and two moles of water were also produced. (1mk)