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:

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