Chapter 17, Problem 68A

Interpretation Introduction

Interpretation:

The common ion effect on the solubility of ionic compound is to be explained.

Concept introduction:

The common ion is that ion which is common in both salts of a solution.

Answer to Problem 68A

Common ion decreases the solubility of ionic compound to maintain the equilibrium state of the reaction.

Explanation of Solution

If the concentration of one of the ions is decreased, more salts will dissolve to increase the concentrations of both ions till once again ionic product becomes equal to solubility product.

Consider an example to discuss this concept:

Example: consider an example of two ionic compound

$\text{NaCl}\rightleftharpoons {\text{Na}}^{\text{+}}{\text{+Cl}}^{\text{-}}$

$\text{HCl}\rightleftharpoons {\text{H}}^{\text{+}}{\text{+Cl}}^{\text{-1}}$

There is a common ion which is chlorine.

The dissociation of sodium chloride is deceased to an extent that the ionic product of $\text{NaCl}$ exceeds its solubility product and it is thrown down as a precipitate.

Conclusion

To attain the equilibrium state, the common ion effect decreases the solubility of the ionic compound.