Sulphurous acid (H2SO3) is a dibasic acid, i.e., it contains two replaceable hydrogen ions per molecule of the acid. Hence, it can form normal salt as well as acid salt on reaction with an alkali.

Sulphurous acid (H2SO3) is a dibasic acid, i.e., it contains two replaceable hydrogen ions per molecule of the acid. Hence, it can form normal salt as well as acid salt on reaction with an alkali.
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