(a) which hydrocarbons burn with (i) non-sooty blue flame and (ii) sooty yellow flame? (b) what happens when methane reacts with chlorine? (c) what is rectified spirit? (d) why does soap not work in hard water? (e) what is glacial acetic acid?

A) Hydrocarbons are compounds made of hydrogen and carbon. They include both saturated and unsaturated hydrocarbon.
i) Alkanes are the hydrocarbons that burns with a non-sooty blue flame, this is because  they are saturated, that is they lack both double bond or triple bond between carbon. Instead each carbon has a maximum number of bonds with single bonds between carbon atoms.

ii) Alkenes and alkynes are hydro carbon which burns with a sooty yellow flame. This is due to the fact that they are unsaturated, that is, alkenes have a double bond between carbon atoms while alkynes have a triple bond between carbon atoms.

b) Methane is an saturated hydrocarbon (alkane). it has one carbon atom and four hydrogen atoms. When reacted with chlorine, one chlorine atom replaces/substitutes one hydrogen atom forming chloro-methane and hydrogen chloride gas. A reaction called substitution.
CH₄ + Cl₂ = CH₃Cl + HCl

c) Rectified spirit is a highly concentrated ethanol which has been purified by means of repeated distillation, a process that is called rectification. It has a composition of ethanol 95% and water with 5%. The process of fermentation in beer making industry mostly produces rectified spirit.

d) Hard water is water that has high material content, it contains calcium and magnesium principally as bicarbonates, chlorides and sulfates. Soap do not work with hard water because it is difficult to form lather with it. The dissolved calcium ions and magnesium ions in hard water react with soap to form precipitates, thus more soap is needed.

e) Glacial acetic acid is a weak colorless reducing agent when it remains free of water (not diluted). This makes it suitable for use in plastics and food industries. Despite being a weak acid it is mildly corrosive with metals such as iron, magnesium and zinc. It liberates hydrogen gas and a salt when reacted with such metals.