A chemical reaction may be 'reversible' in nature. State the meaning of the term in italics. Give a reason why a catalyst is used in certain chemical reactions.

Give a balanced equation for the following -

(a) A reversible catalytic reaction involving -

(i) nitrogen as one of the reactants

(ii) sulphur dioxide as one of the reactants.

State which type of chemical reactions proceed with -

(a) Evolution of heat energy

(b) Absorption of heat energy.

State in each of the following reactions whether heat is evolved or absorbed

(i) water is added to quicklime

(ii) two neutral gases on passage through an electric arc give nitric oxide

(iii) two neutral gases combine to give - a basic gas.

State the meaning of the term 'oxide. Give a balanced equation for formation of the following oxides -

(a) Sulphur dioxide from a non-metal

(b) Zinc oxide from a metal

(c) Lead oxide from a mixed oxide.

Give two examples each of the following oxides -

(a) Acidic oxides

(b) Basic oxides

(c) Amphoteric oxides

(d) Neutral oxides.

State which of the following oxides i.e. (a) to (d) -

(i) React with water to give a base

(ii) React with a base to give salt & water

(iii) React with acids & bases to give salt & water.