State which of the following statements does not describe the property of alkenes :

A: They are unsaturated hydrocarbons
B: They decolourise bromine water
C: They can undergo addition as well as substitution reactions
D: They undergo combustion with oxygen forming carbon dioxide and water.

State the conditions required for :

(i) Catalytic hydrogenation of ethyne.

(ii) Preparation of ethyne from ethylene dibromide.

Select from the list — Ammonia, ethane, hydrogen chloride, hydrogen sulphide, ethyne

(i) The gas is used for welding purposes.

(ii) This gas is also a saturated hydrocarbon.

Write structural formula of:

(i) ethanol

(ii) 1-propanal.

(iii) ethanoic acid.

(iv) 1, 2, dichloroethane.