Question

Account for the following:

H₃PO₃ is a diprotic acid.

Answer 1

1. H₃PO₃ (phosphorous acid) is a diprotic acid because it can release two protons (H⁺ ions) in aqueous solution.
2. Its structure contains two acidic hydrogen atoms bonded to oxygen and one hydrogen bonded directly to phosphorus, which is not ionisable.
3. Therefore, only the two hydrogens attached to oxygen are ionisable, making it diprotic.
4. It ionises in two steps, first releasing one H⁺ ion, then a second H⁺ ion, confirming its dibasic (diprotic) nature.