CHEM TEST

FORM 4 CHEMISTRY CAT
13TH JULY 2007
ANSWER ALL QUESTIONS IN THE SPACES PROVIDED
Dacron is a synthetic fibre formed by polymerization reaction between a dicarboxylic acid and a diol+ (an alcohol with two functional groups)
HOOC – C6H4 – COOH HO – (CH2) 2 – OH
a) Show how the polymerization occurs between the two
SOLUTION
HOOC – C6H4 – CO OH H O – (CH2) 2 – OH

H2O
HOOC – C6H4 – COO – (CH2) 2 – OH
b) Name the type of polymerization involved in forming Dacron
- Condensation polymerization
a) What is vulcanization of rubber?
- Heating rubber latex with sulphur.
b) State two properties that vulcanized rubber possess as a result of vulcanization.
- Rubber hardens.
- Greater tensile strength.
c) What property of concentrated sulphuric acid is illustrated by its action on
a. Sugar
- Dehydrating agent
b. Copper metal
- Oxidizing agent
c. Write a stoichometric equation for the reaction that occurs in (b) above

Cu(s) +2H2SO4(l) CuSO4 (aq) + SO2 (g) + 2H2O(l)

d) What determines the chemical properties of an organic compound?
- The functional groups e.g. double bond or triple bond
- OH-, COOH-
Chlorine gas was bubbled through water for sometime. The green-yellow solution formed was poured into a long glass tube as shown in the diagram below. Study the diagram and answer the questions that follow.
Sunlight

Q Long glass tube



Yellow green

a) Name the compounds formed in the green yellow solution
- HCL
- HOCL
b) Write a balanced equation for the formation of solution substance Q
2HOCL(aq) 2HCL(aq) + O2(g)

c) If the remaining solution was electrolyzed using graphite electrodes how would its PH change.
- The pH would rise due to removal of hydrogen ions
- 2H+ (aq) +2e- H2 (g)
In the contact process for the manufacture of sulphuric acid id represented as follows:
2SO2 (g) + O2 (g) 2SO3 (g) DH = -197Kjmol-1



a) If the reaction takes place in a closed vessel state one effect a catalyst has on the above reversible reaction.
- The equilibrium is reached more readily; it alters the rate at which the equilibrium is reached/attained.
b) What is the effect on the rate of the reaction above if
(i) Volume of the container is doubled?
- The reaction proceeds in the backward reaction due to reduced pressure i.e. SO3 breaks down into SO2 and O2.
(ii) Temperature is doubled?
- It is exothermic so temperature affects forward reaction equilibrium shifts to the left
5. a) What is a fuel?
- A substance that releases energy when burnt.
c) List two characteristics of a good fuel
- Heating value.
- Ease and rate of combustion.
- Availability.
- Ease of transportation
- Ease of storage.
- Environmental effects.
6. a) In terms of ions present distinguish between the following pairs of
Electrolytes.
i) Molten electrolyte and aqueous electrolyte
- Molten electrolyte; has only two types of ions
- Aqueous electrolyte; has additional ions of H+ and OH-
ii). Weak electrolyte and strong electrolyte
- Weak electrolyte; ionizes partially.
- Strong electrolyte; ionizes fully.
b) In terms of electrical energy distinguish between an electrolytic cell and an electrochemical cell.
- Electrolytic cell; system of converting chemical energy into electrical energy.
- Electrochemical cell; combination of two half-cells to give a full cell, which is capable of generating electric current from a redox reaction.
7. a) Oxide of Nitrogen contains a 30.4% nitrogen . Its density at s.t.p is 4.11gm-3. -------Determine the MF of the compound. (N=14, O=16 Molar gas Volume=22.4dm3)
SYMBOL N O

RAM 14 16
% MASS 30.4 69.6
MOLES 2.17 4.35
MOLE RATIO 1 2.0
Molecular mass of hydrogen gas = D X V = 4.11gdm-3 x 22 dm3
= 2.06g
EFM = 14 + (6 X 2) = 46
EF = NO2
EFM = 14 +32 = 46
MFM/EFM = n = 92.06/46 =2
MF = (NO2) 2 = N2O2
d) Magnesium ribbon was burned in a gas jar of Nitrogen. A few drops of water were then added to the solid formed in the jar. Write an equation for the second reaction.
Mg3N2 + 6H2O(l) 3Mg(OH)2 + 2NH3(g)









Prepared by
Akama B.N.