Q60 / 180 · KCET 2023 · Chemistry

Which one of the following oxoacids of phosphorus can reduce $\mathrm{AgNO}_3$ to metallic silver?

  • Correct answer
    A
    $\mathrm{H}_3 \mathrm{PO}_2$
  • B
    $\mathrm{H}_4 \mathrm{P}_2 \mathrm{O}_7$
  • C
    $\mathrm{H}_4 \mathrm{P}_2 \mathrm{O}_6$
  • D
    $\mathrm{H}_3 \mathrm{PO}_4$

Solution

Hypophosphorus acid $\left(\mathrm{H}_3 \mathrm{PO}_2\right)$ is a strong reducing agent which can effectively reduce $\mathrm{Ag}^{+}$ ions to $\mathrm{Ag}$ and itself gets oxidise to phosphorus acid $\left[\mathrm{H}_3 \mathrm{PO}_3\right]$ as follows $\begin{aligned} 3 \mathrm{AgNO}_3+4 \mathrm{H}_3 \mathrm{PO}_2+\mathrm{H}_2 \mathrm{O} \longrightarrow & 3 \mathrm{Ag}+4 \mathrm{H}_3 \mathrm{PO}_3 \\ & +3 \mathrm{HNO}_3\end{aligned}$

Hence, the correct answer is option: 'A'.

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