Question

$H_{3}P{O}_3$, phosphorus acid is

• A. a diprotic acid
• B. a triprotic acid
• C. a monoprotic acid
• D. not acidic

Answer 1

Answer: (A)

Due to more electronegativity difference between $H$ and $O$, the $H$ atom attached to $O$ is detached rather than the $H$ attached to $P$.
So, when $H_{3}P{O}_3$ is added to water, only $2H^{+}$ions are released, $SO,H_{3}P{O}_3$ is a diprotic acid.