CHEMISTRY THEORY PAPER 1

OCT/NOV. 2008

2 HOURS

1. A small crystal of potassium manganate (VII) was placed in a beaker water. The beaker was left standing for two days without shaking. State and explain the observations that were made. 2mks)

2. When a hydrated sample of calcium sulphate CaSO4 XH2O was heated until all the water was lost, the following data recorded;

Mass of crucible = 30.296 g

Mass of crucible +hydrated salt = 33.111 g

Mass of crucible + anhydrous salt = 32.781 g

Determine the empirical formula of the hydrated salt (Relative formula mass of CaSO4 =136, H2O =18). (3mks)

3. Complete the following table by filling in the missing test and observations

(3mks)

No. Gas Test Observation
I Chlorine Put a moist red litmus paper into the gas
II Sulphure (IV) oxide Paper turns green
III Butane Add a drop of bromine water

4. The structure of a detergent is

a) Write the molecular formula of the detergent. (1mk)

b) What type of detergent is represented by the formula? (1mk)

c) When this type of detergent is used to wash linen in hard water, spots (marks) are left on the linen. Write the formula of the substance responsible for the spots (1mk)

5. Phosphoric acid is manufactured from calcium phosphate according to the following equation.

Ca3(PO4)2(s) + 3H2SOv(l) 2H3PO4(AQ) + 3 CaSO4(S)

Calculate the mass in (Kg) of phosphoric acid that would be obtained if 155 Kg of calcium phosphate reacted completely with the acid

(Ca=40, P=31, S=32, O=16, H=1) (2mks)

6. The structure below represents a sweet smelling compound

Give the names of the two organic compounds that can be used to prepare this compound in the laboratory. (2mks)

7. a) What are isotopes? (1mk)

b) Determine the number of neutrons in 18

O.

8 (1mk)

8. a) State the observation made at the end of the experiment when a mixture of

iron powder and sulphur is heated in a test tube. (1mk)

b) Write an equation for the reaction the product in (a) above and dilute hydrochloric acid. (1mk)

c) When a mixture of iron powder and sulphur is heated, it glows more brightly than that of iron fillings and sulphur. Explain this observation

(1mk)

9. Zinc reacts with both concentrated and dilute sulphuric (VI) acid. Write equations for two reactions. (2mk)

10. When magnesium was burnt in air, a solid mixture was formed. On addition of water to the mixture a gas which turned moist red litmus paper blue was evolved. Explain these observations.

11. The table below gives atomic numbers of elements represented b the letters a, B, C and D.

Element A B C D
Atomic number 15 16 17 20

Use the information to answer the questions that follow.

a) Name the type of bonding that exists in the compound formed when A and D react (1mk)

b) Select the letter which represents the best oxidizing agent. Give a reason for your answer. (2mks)

12. In an experiment, a test-tube full of chlorine water was inverted in chlorine water as shown in the diagram below and the set up left in sunlight for one day.

C

After one day, a gas was found to have collected in the test-tube

a) Identify the gas.

b) What will happen to the PH of the solution in the beaker after one day? Give an explanation. (2mks)

C 001 13. In a laboratory experiment hydrogen gas was passed over heated copper (II) oxide as shown the diagram below.

Describe a chemical test that can be used to identify the product e. (2mks)

14. Samples of urine from three participants F, G and H at an international sports meeting were spotted onto a chromatography paper alongside two from illegal drugs A1 and A2.

C 002

A chromatogram was run using methanol. The figure below shows the chromatogram.

a) Identify the athlete who had used an illegal drug. (1mk)

b) Which drug is more soluble in methanol? (1mk)

15. The table below gives the solubilities of substances J, K and L at different temperatures

Substance Solubility in grammes per 100 g water at
00C 200C 400C 600C
J

K

L

0.334

27.60

35.70

0.16

34.0

36.0

0.097

40.0

40.0

0.0058

45.5

37.3

Select the substance which, when dissolved in water, heat is given out. Give a reason .(2mks)

16. Starting with copper metal, describe how a sample of crystals of copper (II) chloride may be prepared in the laboratory. (3mks)

17. A compound whose general formula is M (OH)3 reacts as shown by the equation below.

(a) What name is given to compounds which behave like M (OH) 3 in the two

Reactions (1 mk)

(b) Name two elements whose hydroxides behave like that of M (2 mks)

18. The grid below is part of the periodic table. Use it to answer the questions that follow, (the letters are not the actual symbols of the elements).

a) Indicate on the grid the position of an element represented by letter V whose atomic number is 14. (1mk)

b) Select a letter which reaction between Q and T. (1mk)

19. Select a letter which represents a mono atomic gas. (1mk)

a) Write the cell representation for the electrochemical cell that would give the highest E (1mk)

b) State and explain the observations made when a copper rod is placed in a beaker containing silver nitrate solution. (2mks)

20. a) State the Graham’s law diffusion. (1mk)

b) The molar masses of gases W and X are 16.0 and 44.0 respectively. If the rate of diffusion of W through a porous material is 12cm3s-1 calculate the rate of diffusion of X through the same material. (2mks)

21. The diagram below represents an experiment that was set up to investigate movement of ions during electrolysis.

C 003

When the circuit was completed, it was noticed that a blue colour spread towards the right.

a) Explain this observation (2mks)

b) Write the equation for the reaction that occurred at the anode. (1mk)

C 004 22. The diagram below is part of a set up used in the laboratory preparation of a gas.

Complete the diagram to show how a dry sample of the gas can be collected.

(3mks)

23. In a closed system, aqueous iron (III) chloride reacts with sulphide gas as shown in the equation below.

2FeCl3(aq) + H2S(g) 2FeCl2(aq) 2HCl(aq) + S(s)

State and explain the observation that would be made if dilute hydrochloric acid is

added to the system at equilibrium. (2mks)

24. a) A radioactive substance emits three different particles.

Give the symbol of the particle with the highest mass. (1mk)

b) (i) Find the values of Z1 and Z2 in the nuclear equation below

iii) What type of nuclear reaction is represented in b (i) above?

(1mk)

Give the name of the:

a) Process taking place between t0 and t1. (1mk)

b) Energy change that occurs between t3 and t4

26. When solid B1 was heated, a gas which formed a white precipitate when passed through lime water was produced. The residue was dissolved in dilute nitric (V) acid to form a colourless solution B2. when dilute hydrochloric acid was added to solution B2 a white precipitate which dissolved on warning was formed.

a) Write the formula of the;

I Cation in solid B1 (1mk)

II anion in solid B1 (1mk)

b) Write an ionic equation for the reaction between the resdue and dilute nitric (V) acid. (1mk)

27. In an experiment to determine the percentage of magnesium hydroxide in an anti-acid, a solution containing 0.50 g of the anti-acid was neutralized by 23.0 cm3 of 0.010m hydrochloric acid (Relative formula mass of magnesium hydroxide =58)

a) Mass of magnesium hydroxide in the anti-acid; (2mks)

b) Percentage of magnesium hydroxide in the anti-acid (1mk)

28. During the extraction of aluminium from its ores; the ore is first purified to obtain alumina.

a) Name

(i) Substance C1 (1mk)

………………………………………………………………………..

(ii) Process D1 (1mk)

…………………………………………………………………………

b) Give two reasons why aluminium is used extensively in the making of cooking pans. (1mk)

29. A certain mass of a metal E1 reacted with excess dilute hydrochloric acid at 25oC. The volume of hydrogen gas liberated was measured after every 30 seconds. The results were presented as shown in the graph below.

a) Name one piece of apparatus that may have been used to measure the volume of gas liberated. (1mk)

b) (i) On the same axis, sketch the curve that would be obtained if the experiment was repeated at 350C. (1mk)

(ii) Explain the shape of your curve in b(i) above. (1mk)

30. Crude oil contains sulphur. What would be the effect to the environment of using fuel containing sulphur? (1mk)

31. Study the flow chart below and answer the questions that follow.

a) Give the name of the process that takes place in step 1. (1mk)

b) Give;

(i) The name of substance G1

(ii) One use of substance F1

CHEMISTRY PAPER 2 THEORY

OCT /NOV. 2008

233/2

2 HOURS

1. a) Biogas is a mixture of mainly carbon (IV) oxide and methane.

(i) Give a reason why biogas can be used as a fuel. (1mk)

(ii) Other than fractional distillation, describe a method that can be

used to determine the percentage of methane in biogas. (3mks)

b) A sample of biogas contains 35.2% by mass of methane. A biogas cylinder contains 5.0 kg of the gas.

Calculate the;

(i) Number of moles of methane in the cylinder. (Molar mass of methane=16)

(2mks)

(ii) Total volume of carbon (IV) oxide produced by the combustion of methane in the cylinder (Molar gas Volume=24.0 dm-3+ at room temperature and pressure). (2mks)

c) Carbon (Iv) oxide, methane, nitrogen (I) oxide and trichlorofluoromethane are green-house gases.

(i) State one effect of an increased level of these gases to the environment. (1mk)

(ii) Give one source from which each of the following gases is released to the environment;

I Nitrogen (i) oxide (I mk)

II Trichlorofluoromethane. (1mk)

2 a) Write an equation to show the effect of heat on the nitrate of:

(i) Potassium (1mk)

b) The table below gives information about elements A1A2A3, and A4

Element Atomic

Number

Atomic

Radius (nm)

Ionic radius (nm)
A1

A2

A3

A4

3

5

13

17

0.134

0.090

0.143

0.099

0.074

0.012

0.050

0.181

(i) In which period of the periodic table is element A2? Give a reason

(2 mks)

(ii) Explain why the atomic radius of:

I A1 is greater than that of A2;

II A4 is smaller than its ionic radius (2 mks)

(iii) Select the element which s in the same group as A3 (1 mk)

(iv) Using dots (.) and crosses(x) to represent outermost electrons. Draw a

diagram to show the bonding in the compound formed when A1 reacts with A4 (1 mk)

3. (a) Describe the process by which Nitrogen is obtained from air on a large scale.

(4 mks)

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

C 006

(i) Identify gas J. (1 mk)

(ii) Using oxidation numbers, show that ammonia is the reducing agent in step (VI) (2mks)

(iii) Write the equation for the reaction that occurs in step (V). (1mk)

(iv) Give one use of ammonium nitrate. (1mk)

c) The table below shows the observations made when aqueous ammonia was added to cations of elements F2F and G until in excess.

Cation of Addition of a few drops of

Aqueous ammonia.

Addition of excess aqueous ammonia.
E White precipitate Insoluble
F No precipitate No precipitate
G White precipitate Dissolves

(i) Select the cation that is likely to be Zn2+ (1mk)

(ii) Given that the formula of the cation of element E is E 2+, write the ionic equation for the reaction between E2+ (aq) and aqueous ammonia. (1mk)

4a) (i) State the Le chatelier’s principle. (1mk)

(ii) Carbon (II) oxide gas reacts with steam according to the equation;

CO(g) + H2O(g) H2(g)+ CO+2(g)

What would be the effect of increasing the pressure of the system at equilibrium? Explain. (2mks)

b) The table below gives the volumes of oxygen gas produced at different times when hydrogen peroxide decomposed in the presence of a catalyst.

 

Time(Sec) 0 10 20 30 40 50 60
Volume of oxygen (cm3) 0 66 98 110 119 120 120

(i) Name the catalyst used for this reaction (1mk)

(ii) On the grid provided, draw the graph of volume of oxygen gas produced (vertical axis) against time. (3mks)

(iii) Using the graph, determine the rate of decomposition of hydrogen peroxide after 24 seconds. (2mks)

(iv) Give a reason why the total volume of oxygen gas produced after 50 seconds remains constant. (1mk)

5. (a) Alkanes, alkenes and alkynes can be obtained from crude oil. Draw the

structure of the second member of the alkyne homologous series. (1mk)

  1. Study the flow chart below and answer the questions that follow

C 007

  1. State the conditions for the reaction in step 1 to occur ( 1 mk)
  2. Identify substance II ( 1 mk)
  3. Give:

I. One advantage of the continued use of substance such as J (1 mk)

II The name of the process that takes place in step III (1 mk)

III The name and the formula of substance K (2mks)

Name:………………………………

Formula:……………………………

  1. The relative molecular mass of J is 16,800. Calculate the number of monomers that make up J.
  2. The table below give the formula of four compounds L,M,N and P
Compound Formula
L C2H6O
M C3H6
N C3H6O2
P C3H8

Giving a reason in each case, select the letter which represents a compound that:

(i) Decolorizes bromine in the absence of UV light ( 2 mks)

(ii) Gives effervescence when reacted with aqueous sodium carbonate

( 2 mks)C 008

The diagram below represents a set up that can be used to electrolyze aqueous copper (II) sulphate.

(a) (i) Describe how oxygen gas is produced during the electrolysis ( 2 mks)

(ii) Explain why copper electrodes are not suitable for this electrolysis

( 2 mks)

  1. Impure copper is purified by an electrolytic process

(i) Name one ore from which copper is obtained ( 1 mk)

(ii) Write the equation for the reaction that occur at the cathode during the

purification of copper ( 1 mk)

(iii) In an experiment to electroplate a copper spoon with silver, a current of 0.5 A was passed for 18 minutes. Calculate the amount of silver deposited on the spoon (π = 96500 coulombs, Ag = 108) (3mks)

  1. Give two reasons why some metals are electroplated (2mks)

7. (a) Define the standard enthalpy of formation of a substance ( 1 mk)

(b) Use the thermo chemical equations below to answer the questions that

follow.

(i) Name two types of heat changes represented by ∆H3 ( 2 mks)

(ii) Draw an energy level diagram for the reaction represented by equation 1

(iii) Calculate the standard enthalpy of formation of ethane ( 2 mks)

  1. When a sample of ethane was burnt, the heat produced raised the temperature of 500g of water by 21. 5 K, (specific heat capacity of water = 4.2Jg-1K).

Calculate the:

    1. Heat change for the reaction ( 2 mks)
    2. Mass of ethane was burnt. ( relative formula mass of ethane= 30)

( 2 mks)