Question

The correct statement(s) related to oxoacids of phosphorous is(are)

• A. Upon heating, $H_3PO_3$ undergoes a disproportionation reaction to produce $H_3PO_4$and $PH_3$.
• B. While $H_3PO_3$ can act as a reducing agent, $H_3PO_4$ cannot.
• C. $H_3PO_3$ is a monobasic acid.
• D. The H atom of the P-H bond in $H_3PO_3$is not ionizable in water.

Answer 1

Answer: (A), (B), (D)

Upon heating, $H_3PO_3$ undergoes a disproportionation reaction to produce $H_3PO_4$and $PH_3$.

Answer 2

$\begin{array}{l}4H_{3}PO_{3} \overset{\Delta }{\rightarrow}PH_{3} + 3H_{3}PO_{4}\end{array}$
In H3PO4, phosphorous is present in the highest oxidation state, i.e., +5. So H3PO4 cannot act as a reducing agent. Structure of H3PO3,

It is a dibasic acid.
H atom present in the P–H bond is not ionizable.
These P-H bonds are not ionisable to give H+ and do not play any role in basicity. Only those H atoms which are attached with oxygen in P-OH form are ionisable and cause the basicity. Thus, H3PO3 and H3PO4 are dibasic and tribasic, respectively as the structure of H3PO3 has two P – OH bonds and H3PO4 three.