Question

$H_3PO_3$, phosphorus acid is

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

Answer 1

Answer: (A)

a diprotic acid

Answer 2

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 $H _{3} PO _{3}$ is added to water, only $2 H ^{+}$ions are released, $SO , H _{3} PO _{3}$ is a diprotic acid.