Question

Give two reactions to show that nitric acid is :

(i) An acid.

(ii) An oxidizing agent

Answer 1

(i) (a) Dilute nitric acid reacts with magnesium metal to liberate hydrogen gas and magnesium nitrate is formed.

Mg + 2NHO₃ ⟶ Mg(NO₃)₂ + H₂ ↑

(b) Dilute nitric acid reacts with marble pieces to liberate carbon dioxide gas and calcium nitrate is formed.

CaCO₃ + 2HNO₃ ⟶ Ca(NO₃)₂ + H₂O + CO₂ ↑

(ii) (a) When carbon is heated with concentrated nitric acid, it is oxidized to carbonic add and the acid is reduced to nitrogen dioxide and water.

C + 4HNO₃ ⟶ H₂CO₃ + 4NO₂ + H₂O

(b) When sulphur is heated with concentrated nitric acid, it is oxidized to sulphuric acid and the nitric’add is reduced to nitrogen dioxide and water. Carbonic add further decomposes to carbon dioxide.

S + 6HNO₃ (Conc) ⟶ H₂SO₄ + 6NO₂ + 2H₂O