a) Calcium carbonate/magnesium carbonate√1

b) Washing with weak acid solution such as methanoic acid√1

c)

– Helps in forming strong teeth &bones (1)

- does not dissolve lead pipes.

- Good for brewing & tanning industry

a) i) Butanoic acid 1m

ii) propylethanoate. 1mk

a) Sample I is a pure substance since pure substance have a sharp melting and boiling points. (1mk)

Sample II is impure since the melting point is lower than that of a pure substance and its boiling point is higher than that of pure substance which is characteristic phenomena of an impure substance. (1mk)

b) Since ice causes skidding, common salt becomes an impurity to water (ice) causing it to melt at a lower temperature. (1mk)

a) The volume of a fixed mass of gas is inversely proportional to its pressure at constant temperature

c) When volume is decreased at constant temperature, gas particles have a shorter distance to cover before colliding with each other and the walls of the container. The collisions become more frequent which increases pressure.

a)Aluminium reacting with O2 forming a hard resistant layer of Al2O3 which does not react (1)

b) Aluminium oxide layer on utensils reacts with the alkali in ash forming complex soluble salts since it is amphoteric.(1) hence exposing aluminium to corrosion.(1)

c) Aluminium, magnesium (1)

Monomer molecular mass

i) Increasing the pressure

ii) Decreasing the temperature

a) X- fractionating column (1mk)

Y- Liebig condenser

b) to condense back the component of higher boiling point. (1mk)

c) shown on the diagram (½ mk)

d) fractional distillation (½ mk

a) – Wrong drying agent, Quick lime reacts with chlorine

- Wrong method of gas collection. Chlorine is denser than air and cannot be collected by upward delivery.

b) Potassium Dichromate

i) This occurs when ammonia decomposes when heated

ii) When ammonia is burned in air enriched with oxygen.

iii) These are formed when ammonia is oxidized in the presence of platinum catalyst.