Give balanced equations for the following reactions of synthesis involving formation of :

(a) An acid – from sulphur dioxide gas

(b) An alkali – from a basic oxide – sodium oxide

(c) A salt – from a trivalent metal and a coloured gas.

Convert — (a) nitrogen to ammonia (b) hydrogen to hydrogen chloride – by a direct combination reaction.

Define a thermal dissociation reaction with a suitable example.

Define a displacement reaction with example. State why Zn displaces H₂ from dil. H₂SO₄ but Cu does not.