Sodium hydroxide can react with ............... acid to form an acid salt.

Sulphuric acid

Reason — An acid salt is formed when a dibasic or tribasic acid is only partially neutralised by a base.

• Nitric acid (HNO₃) and hydrochloric acid (HCl) are monobasic acids → they can form only normal salts, not acid salts.
• Acetic acid (CH₃COOH) is also monobasic → only forms sodium acetate.
• Sulphuric acid (H₂SO₄) is dibasic → with sodium hydroxide (NaOH), it can form an acid salt, sodium hydrogen sulphate (NaHSO₄), on partial neutralisation.

So, sodium hydroxide reacts with sulphuric acid to form an acid salt.

NaOH + H₂SO₄ ⟶ NaHSO₄ + H₂O