Question:
The solubility of $\mathrm{AgCN}$ in a buffer solution of $\mathrm{pH}=3$ is $\mathrm{x}$. The value of $\mathrm{x}$ is:
[Assume: No cyano complex is formed; $\mathrm{K}_{\mathrm{sp}}(\mathrm{AgCN})$ $=2.2 \times 10^{-16}$ and $\mathrm{K}_{\mathrm{a}}(\mathrm{HCN})=6.2 \times 10^{-10}$ ]
Correct Option: , 2
Solution:
$\frac{\mathrm{K}_{\mathrm{sp}}}{\mathrm{Ka}}=\frac{\mathrm{s}^{2}}{\left(\mathrm{H}^{+}\right)} ; \quad \mathrm{s}=\sqrt{\frac{\mathrm{K}_{\mathrm{sp}}}{\mathrm{K}_{\mathrm{a}}}\left(\mathrm{H}^{+}\right)}$
$\mathrm{s}=\sqrt{\frac{2.2 \times 10^{-16}}{6.2 \times 10^{-10}} \times 10^{-3}}$
$\mathrm{s}=1.9 \times 10^{-5}$
Hence answer is $(2)$