Distinguish between the following:

(a) Concentrated H2SO4 and concentrated HNO3 [using sulphur]
(b) Concentrated HCl and concentrated H2SO4 [using sodium nitrate solution]

Solution

Nitric acid (HNO₃) is an oxidizing acid and it can oxidise sulphur into its higher oxidation states (+4 or +6). According to the temperature of the concentrated nitric acid solution, sulphur is oxidized to sulphur dioxide (SO_{​​​​​2}) or sulphuric acid (H₂SO₄) acid.

Reaction

S + 6HNO₃ → H₂SO₄ + 2H₂O + 6NO2


However with sulphuric acid, no evolution of gas occurs.


b) NaNO₃ + HCl gives NaCl + HNO₃
2NaNO₃ + H₂SO₄ gives 2 HNO₃ + Na₂SO₄