Question

Define : Common ion effect.

Hint:

Common ion effect is vital in qualitative analysis for the selective precipitation of group radicals.

Answer 1

Step 1: Understanding the Concept:
This effect is based on Le Chatelier's principle applied to ionic equilibria.
Step 2: Detailed Explanation:
When a strong electrolyte that provides an ion already present in the solution of a weak electrolyte is added, the equilibrium of the weak electrolyte shifts in the direction of the undissociated molecule.
Example: Adding \(CH_3COONa\) (strong) to \(CH_3COOH\) (weak). The increased concentration of \(CH_3COO^-\) ions drives the dissociation of acetic acid backwards.
\[ CH_3COOH \rightleftharpoons CH_3COO^- + H^+ \]
Step 3: Final Answer:
Common ion effect is the decrease in the degree of dissociation of a weak electrolyte upon adding a strong electrolyte with a common ion.