Question

Assign appropriate reason for the following observation:

Phosphinic acid behaves as a monoprotic acid.

Answer 1

Phosphinic acid (H₃PO₂) behaves as a monoprotic acid because:

1. It contains only one ionisable \[\ce{-OH}\] group attached to phosphorus.
2. The two \[\ce{P-H}\] bonds are not ionisable and do not release H⁺ ions.
3. Hence, only one hydrogen from the \[\ce{-OH}\] group ionises, making it monoprotic.
4. The other hydrogens remain bound and do not contribute to acidity.