The true statement for the acids of phosphorus, $\mathrm{H}_3 \mathrm{PO}_2, \mathrm{H}_3 \mathrm{PO}_3$ and…

1. the order of their acidity is $\mathrm{H}_3 \mathrm{PO}_4>\mathrm{H}_3 \mathrm{PO}_3>\mathrm{H}_3 \mathrm{PO}_2$
2. all of them are reducing in nature
3. all of them are tribasic acids
4. the geometry of phosphorus is tetrahedral in all the three.

Solution

$\mathrm{H}_3 \mathrm{PO}_2, \mathrm{H}_3 \mathrm{PO}_3$ and $\mathrm{H}_3 \mathrm{PO}_4$ contain one, two and three ionisable hydrogen atoms respectively. $\begin{aligned} & \mathrm{H}_3 \mathrm{PO}_2 \rightleftharpoons \mathrm{H}^{+}+\mathrm{H}_2 \mathrm{PO}_2^{-} \\ & \mathrm{H}_3 \mathrm{PO}_3 \rightleftharpoons \mathrm{H}^{+}+\mathrm{H}_2 \mathrm{PO}_3{ }^{-} \rightleftharpoons 2 \mathrm{H}^{+}+\mathrm{HPO}_3{ }^{2-} \\ & \mathrm{H}_3 \mathrm{PO}_4 \rightleftharpoons \mathrm{H}^{+}+\mathrm{H}_2 \mathrm{PO}_4^{-} \rightleftharpoons 2 \mathrm{H}^{+}+\mathrm{HPO}_4{ }^{2-} \\ & \rightleftharpoons 3 \mathrm{H}^{+}+\mathrm{PO}_4{ }^{3-} \end{aligned}$ But there is very little difference in acidity.
$\text {As } s p^3 \text { hybridised, therefore all are tetrahedral. }$

Asked in: NEET 2020 (Phase 2)

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