Question

Consider the following salts:
Na₂CO₃, NaCl, NH₄Cl, CH₃COONa, K₂SO₄, (NH₄)₂SO₄
Which of these salts will give:
(a) acidic solutions?
(b) neutral solutions?
(c) basic solutions (or alkaline solutions)?

Answer 1

(a) The salt solutions of NH₄Cl and (NH₄)₂SO₄ give acidic solutions, because these salts are each formed from a weak base and a strong acid. The ionisation of a weak base is not complete, whereas a strong acid ionises completely. Hence, there are more H⁺ ions than OH^- ions, making the solutions acidic.

(b) The salt solutions of NaCl and K₂SO₄ are neutral, because these salts are formed from a strong base and a strong acid, and on ionisation, there is an equal number of H⁺ and OH^- ions, making the solutions neutral.

(c) The salt solutions of CH₃COONa and Na₂CO₃ are basic, because these salts are each formed from a weak acid and a strong base. The ionisation of a weak acid is not complete, whereas a strong base ionises completely. Hence, there are more OH^- ions than H⁺ ions, making the solutions basic.