CHEMISTRY 2009

PAPER 1

1. The ionization energies for three elements A. B and C are shown in the table below:

Element A B C
Ionisation energy (kJ/mole) 519 418 494

a) what is meant by ionization energy? (1 mk)

b) which element is the strongest reducing agent? Give a reason. (2 mks)

2. Hardness of water may be removed by either boiling or addition of chemicals

a) write an equation to show how boiling removes hardness of water. (1 mk)

b) name two chemicals that are used to remove hardness of water. (2 mks)

3. The atomic number of sulphur is 16.

Write the electron arrangement of sulphur in the following: (2 mks)

a) H2s;

b) SO23

4. An experiment was set up as shown in the diagram below:

a) Identify substance D. (1 mk)

b) Describe how the other product of the burning candle could be prevented from getting into the environment. (2 mks)

5. In terms of structure and bonding, explain why the melting point of oxygen is much

lower than that of sodium. (3 mks)

6. An isotope of element E has 34 neutrons and its mass number is 64. E forms a cation with 28 electrons. Write the formula of the cation with 28 electrons. Write the formula of the cation indicating the mass and atomic numbers. (1mk)

7. When aluminium oxide was electrolysed, 1800kg of aluminium metal were obtained.

a) Write equation for the formation of aluminium metal (1 mk)

b) Calculate the quantity of electricity in faradays used (Al=27) (2 mks)

8. Using dots (.) and crosses (x) , show bonding in:

a) The compound formed when nitrogen reacts with fluorine

(Atomic numbers F=9, N=7); (1mk)

b) Sodium oxide.

(Atomic numbers Na= 11, 0 = 8) (1 mk)

9. a) what is meant by molar heat of solution? (1 mk)

b) the lattice energy of sodium bromide and hydration energies of sodium and bromide ions are: 733,406 and 335 kJmol -1 respectively.

i) Complete the energy cycle diagram below by inserting the values of

H1, H2, and H3 (1 ½ mks)

ii) Determine the molar heat of solution of solid sodium bromide. ( ½ mk)

10. Hydrogen and oxygen can be obtained by electrolysis of acidified water.

Using equations for the reactions at the electrodes, explain why the volume of hydrogen obtained is twice that of oxygen. (2mks)

11. Starting with 50 cm3 of 2.8M sodium hydroxide, describe how a sample of pure sodium sulphate crystals can be prepared. (3 mks)

12. The standard reduction potentials of two half –cells are:

Ag+(aq) + e AG(s) ; E = 0.80V

2H2O (l) + 2e H2 (g) + 2OH (aq); E1 = 0.83V

 

Draw a labelled diagram of an electro chemical cell that can be constructed using the two half –cells (3 mks)

13. When 8.53 of sodium nitrate were heated in an open test-tube the mass of oxygen gas produced was 0.83 g . Given the equation of the reaction as

2NaNO3(s) 2NaNO2(s) + O2(g)

Calculate the percentage of sodium nitrate that was converted to sodium nitrite (Na = 23.0 N = 14.0 O = 16.0) (3 mks)

14. a) Draw and name the structure of the compound formed when one mole of

ethyne reacts with one mole of hydrogen bromide. (2mks)

b) Draw the structures of the alkynes whose molecular formula is C4H6 (1 mk)

15. a student used the set up shown in the diagram below in order to study the reactions of some metals with steam. The experiment was carried out for ten minutes

a) What observation would be made if gas F is ignited? (1 mk)

b) When the experiment was repeated using iron powder instead of magnesium

ribbon very little gas F was obtained.

i) Give a reason for this observation (1 mk)

ii) What change in the conditions of the experiment should the student have made in order to increase the volume of gas F Produced? (1mk)

16. The solubility curve of potassium nitrate is shown below.

a) Determine the solubility of potassium nitrate at 500C (1 mk)

b) Determine the molar concentration of saturated potassium nitrate at 500C

(K=39.0 0= 16.0 N= 14.0 and density of water 1 g/cm3). (2 mks)

17. The structure of methanoic acid is

What is the total number of electrons used for bonding in a molecule of methanoic acid? Give reasons. (2 mks)

18. Bottles of sodium carbonate, sodium chloride and sugar have lost their labels.

A student prepares and tests an aqueous solution of a sample from each bottle.

The results obtained are as shown in the table below.

Bottle PH Electrical Conductivity Correct label
1 7 Conducts
2 7 Does not conduct
3 10 conducts

Complete the table by filling the correct label for each bottle. (3 mks)

19) The figure below represents the set up that was used to crack an alkane.

a) What was the purpose of the sand? (1 mk)

b) After some time, a colourless gas G collected in the test-tube.

Describe a chemical test and the observations that would be made in ordered to identify the class of compounds to which gas G belongs. (2 mks)

20. Classify the following processes as either chemical or physical. (3 mks)

Process Type of change
a) Heating copper (II) sulphate crystals
b) Obtaining kerosene from crude oil
c) Souring of milk

21. Give the name of the product formed when magnesium reacts with phosphorus.

(1 mk)

22. a student added very dilute sulphuric (VI) acid to four substances and recorded the observations shown in the table below.

 

Test Substance Gas given off
1 Sodium Yes
2 Iron No
3 Carbon Yes
4 Copper No

For which tests are the observations wrong? Explain (3 mks)

23. Use the flow chart below to answer the questions that follow.

a) What observation would be made in step I? (1 mk)

b) Name another substance that could be used in step 2. (1 mk)

c) Give the name of substance H. (1 mk)

24. The boiling points of some compounds of hydrogen with some elements in groups 4 and 6 of the periodic table are given below.

Compound Boiling point (0C) Compound Boiling point(0C)
CH4 -1640 H2O 100.0
SIH4 -112.0 H2S -61.0

a) Which of the compounds CH4 and SIH4 has stronger intermolecular forces? (1 mk)

b) Explain why the boiling points of H2O and H2S show different trends from

that of CH4 and SIH4 (2mks)

25. For each of the following reactions, state the observation and write the formula of the

Compound responsible for the observation:

a) Bromine water is added to aqueous potassium iodide; (1 ½ mks)

b) Excess aqueous ammonia is added to copper (II) hydroxide (precipitate).

(1 ½ mks)

26. The graph below shows the relationship between pressure and the temperature of a

gas in a fixed volume container.

Pressure

(Pa)

Temperature (0C)

a) State the relationship between pressure and temperature that can be deduced

from the graph. (1 mk)

b) Using kinetic theory, explain the relationship shown in the graph. (2 mks)

27. The following reaction is in equilibrium in a closed container

C(s) + H2O(g) . CO(g) + H2(g)

State giving reasons how an increase in pressure would affect the amount of

hydrogen. (2 mks)

28. The energy level diagram below shows the effect of a catalyst on the reaction path.

a) What does point M represent? (1 mk)

CHEMISTRY

PAPER 2

1. a) Two reagents that can be used to prepare chlorine gas are manganese (IV)

oxide and concentrated hydrochloric acid.

i) Write an equation for the reaction. (1 mk)

ii) Give the formula of another reagent that can be reacted with

concentrated hydrochloric acid to produce chlorine gas. (1 mk)

iii) Describe how the chlorine gas could be dried in the laboratory (2mks)

b) In an experiment, dry chlorine gas was reacted with aluminium as shown in

figure 1.

i) Name substance A. (1 mk)

ii) Write an equation for the reaction that took place in the combustion tube. (1mk)

iii) 0.84 g of aluminium reacted completely with chlorine gas. Calculate the volume of chlorine gas used (Molar gas volume is 24dm3, al = 27).

(3 mks)

iv) Give two reasons why calcium oxide is used in the set up. (2 mks)

2 a) Draw the structures of the following compounds: (2 mks)

i) 2- methylbut -2 ene;

ii) heptanoic acid

b) Describe a physical test that can be used to distinguish between methanol and hexanol. (2 mks)

c) Use the flow chart below to answer the questions that follow.

i) Name:

 

(I) the type of reaction that occurs in step II; (1 mk)

(II) Substance B. (1 mk)

ii) Give the formula of substance C. (1 mk)

iii) Give the reagent and the conditions necessary for the reaction in step (IV) (3mks)

3 The set-up below (figure 2) was used to electrolyse a bromide of metal D DBr2.

 

i) Write equation for the reactions at the

I cathode (1 mk)

II anode (1mk)

ii) The electrodes used in the experiment were made of carbon and metal D.

which of the two electrodes was used as the anode? Give a reason. (2 mks)

iii) Give a reason why this experiment is carried out in a fume cupboard.

(1 mk)

iv) When a current of 0.4 A was passed for 90 minutes, 2.3 1 g of metal D were

deposited.

I Describe how the amount of metal D deposited was determines.

(3 mks)

II Calculate the relative atomic mass of metal D. (I Faraday = 96500

coulombs) (3 mks)

4. a) the schematic diagram shows part of the Solvay process used for the

manufacture of sodium carbonate.

i) Explain how the sodium chloride required for this process is obtained

from sea water. (2 mks)

ii) Two main reactions take place in UNIT I . The first one is the

formation of ammonium hydrogen carbonate.

I. Write an equation for this reaction (1 mk)

II. Write an equation for the second reaction (1 mk)

iii) State how the following are carried out: (2 mks)

I Process I

II) Process II

iv)In an experiment to determine the percentage purity of the sample of sodium carbonate produced in the Solvay process, 2.15 g of the sample reacted completely with 40.0cm3 of 0.5 M sulphuric acid.

I calculate the number of moles of sodium carbonate that

reacted. (2 mks)

II Determine the percentage of socium carbonate in the sample.

(Na= 23.0, C= 12.0, O = 16.0) (2 mks)

b) Name two industrial uses of sodium carbonate (2 mks)

have been identified and others labelled.

i) Give the names of the processes

I H (1 mk)

II G (1 mk)

ii) Name one substance that can undergo process F when left in an open

container in the laboratory. (1 mk)

iii) The process J is called deposition. Using water as an example, write

an equation that represents the process of deposition. (1 mk)

b) Figure 4 shows the beating curve for water.

i) Give the names of the intermolecular forces of attraction in the

segments;

I MN (1mk)

II RS (1 mk)

ii) The heats of fusion and vaporization of water are 334.4 Jg-1 and

1159.4 Jg-1 respectively.

I Explain why there is a big difference between the two.(2mks)

II How is the difference reflected in the curve? (1 mk)

c) Coal, oil and natural gas are major sources of energy. They are known as

fossil fuels. Hydrogen is also a source of energy.

i) State and explain two reasons why hydrogen is a very attractive fuel compared to fossils. (3 mks)

ii) State one disadvantage of using hydrogen fuel instead of fossil fuels.

6. a) Study the table below and complete it. (W-1 and X4+ are not the actual

symbols of the ions). (2 mks)

Iron Number of protons Number of neutrons Mass

Number

Electron arrangement
W …………….. 20 ……………. 2.8.8
X4+ 14 …………… 28 …………..

b) State the observation that would be made in the following tests to distinguish between:

i) Sodium and copper burning pieces of each in air. (2 mks)

ii) Sodium and Magnesium by placing small pieces of each in cold

water which contains two drops of phenolphalein. (2mks)

c) The atomic numbers of Na and Mg are 11 and 12 respectively. Which

of the elements has a higher ionization energy? Explain. (2mks)

d) Naturally occurring uranium consists of three isotopes which are

radioactive.

Isotope      234               235               238

U                  U                    U

Abundance 0.01%         0.72%         99.27%

i) Which of these isotopes has the longest half-life? Give a reason

(1 mk)

ii) Calculate the relative atomic mass of uranium (2mks)

iii) 235 Is alpha emitter. If the product of the decay of this

U

92 nuclide is thorium (Th) . Write a nuclear equation for the

process. (1mk)

7. Iron is obtained from haematite using a blast furnace shown if figure 5 below.

a) Four raw materials are required for the production of iron. Three of these are

iron oxide, hot air and limestone

Give the name of the fourth raw material (1 mk)

b) Write an equation for the reaction in which carbon (IV) oxide is converted

into carbon (II) oxide. (1mk)

 

c) Explain why the temperature in the region marked Y is higher than that of the

incoming hot air. (2 mks)

d) State one physical property of molten slag other than density that allows it to

be separated from molten iron as shown in figure 5. (1mk)

e) One of the components of the waste gases is Nitrogen (IV) oxide

describe the adverse effects it has on the environment. (2mks)

f) Iron from the blast furnace contains about 5% carbon

i) Describe how the carbon content is reduced. (2mks)

ii) Why is it necessary to reduce the carbon content? (1 mk)