Question

Which salts will be more soluble in an acidic solution than in pure water?

• $\mathrm{Ag}_{2} \mathrm{SO}_{4}$
• $\mathrm{Zn}(\mathrm{OH})_{2}$
• CuCN
• $R b C IO_{4}$
• $\mathrm{PbBr}_{2}$

Answer 1

The solubility of an ionic compound depends upon the strength of its conjugate base. If the anion present in the salt is a strong conjugate base, it reacts with the $\mathrm{H}^{+}$ ions present in the acid.

Consider the given compounds as follows:

$\mathrm{Ag}_{2} \mathrm{SO}_{4}, \mathrm{Zn}(\mathrm{OH})_{2}, \mathrm{CuCN}, \mathrm{RbCIO}_{4}$ and $\mathrm{PbBr}_{2}$

In the above compounds, $\mathrm{SO}_{4}^{2-}, \mathrm{CN}^{-}$ and $\mathrm{OH}^{-}$ are strong conjugate bases of the weak acids. Therefore, they react with the $\mathrm{H}^{+}$ ions present in the acid. Hence, they are more soluble in acidic medium as compared to water.

 

The ions $\mathrm{Br}^{-}$ and $\mathrm{CIO}_{4}$ are weak conjugate bases of strong acids. Therefore, they do not react with the $\mathrm{H}^{+}$ ions present in the acid. Hence, the salts that are more soluble in the acidic medium than in pure water are as follows:

$\mathrm{Ag}_{2} \mathrm{SO}_{4}, \mathrm{Zn}(\mathrm{OH})_{2}, \mathrm{CuCN}$