Chapter 17, Problem 64A

Interpretation Introduction

Interpretation:

The common ion is to be explained.

Concept introduction:

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

Answer to Problem 64A

The repression of the degree of dissociation of a weak acid or a weak base by the inclusion of a strong electrolyte containing a common ion.

Explanation of Solution

Let us discuss the common ion effect with the help of example

Example:

When $\text{NaCl}$ and $\text{KCl}$ are dissolved in same solution then the chlorine ions are common to both the salts.

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

$\text{KCl}\rightleftharpoons {\text{K}}^{\text{+}}{\text{+Cl}}^{\text{-}}$

According to Le Chatelier’s principle, if a common ion is added to a weak acid or weal base equilibrium, then the equilibrium will shifts towards the reactants.

Conclusion

The common ion effect is the repression of the degree of dissociation of a weak acid or a weak base by the inclusion of a strong electrolyte containing a common ion.