State the conditions required for :

(i) Catalytic hydrogenation of ethyne.

(ii) Preparation of ethyne from ethylene dibromide.

(i) Vapours of ethyne mixed with hydrogen are passed over a catalyst eg., nickle [Pd. or Pt.] at high temperatures of around 300°C.

(ii) Ethylene dibromide is boiled with conc. alcoholic KOH soln. in a round bottom flask. Ethyne is collected by downward displacement of water.