Explain the term – 'valency'. State giving reasons the valency of –

(a) chlorine in hydrogen chloride

(b) sulphate in sulphuric acid

(c) nitrogen in ammonia

(d) magnesium in magnesium oxide

Give the symbol and valency of the following elements and radicals.

(a) Potassium

(b) Sodium

(c) Hydrogen

(d) Calcium

(e) Aluminum

(f) Magnesium

(g) Zinc

(h) Chlorine [chloride]

(i) Sulphur [sulphide]

(j) Nitrogen [nitride]

(k) Oxygen [oxide]

(l) Ammonium

(m) Bicarbonate

(n) Nitrate

(o) Bisulphate

(p) Bisulphite

(q) Hydroxide

(r) Carbonate

(s) Sulphate

(t) Sulphite

State what is meant by the term – chemical formula. Give the chemical formula of –

(a) sodium hydroxide

(b) sodium nitrate

(c) sodium bicarbonate

(d) sodium sulphite

(e) magnesium nitrate

(f) ammonium sulphate

(g) carbonic acid

(h) calcium phosphate

'Dilute hydrochloric acid is added to sodium hydroxide'. Give a word equation and a molecular equation of the same. Is the equation written, a balanced equation. Give reasons.