Acids, Bases and Salts — Question 11

(a) A non-metal, e.g., sulphur or phosphorous is oxidised by conc. nitric acid to form to form sulphuric acid or phosphoric acid respectively.

S + 6HNO₃ ⟶ H₂SO₄ + 2H₂O + 6NO₂

P + 5HNO₃ ⟶ H₃PO₄ + H₂O + 5NO₂

(b) Normal salts of more volatile acids are displaced by a less or non-volatile acid.

E.g., Both hydrochloric acid and nitric acid are formed by using sulphuric acid [H₂SO₄].

NaCl + H₂SO₄ $\xrightarrow{\space\Delta\space}$ NaHSO₄ + HCl

NaNO₃ + H₂SO₄ $\xrightarrow{\space\Delta\space}$ NaHSO₄ + HNO₃