Which is the correct order of acidity: ${\text{CH}}_3\text{COOH}$, ${\text{ClCH}}_2\text{COOH}$, ${\text{Cl}}_2\text{CHCOOH}$, and ${\text{Cl}}_3\text{CCOOH}$?

Solution

1. Acidity of carboxylic acids is determined by the stability of the conjugate base (carboxylate ion).
2. Electron-withdrawing groups like $-\text{Cl}$ stabilize the negative charge via the inductive effect (-I).
3. As the number of chlorine atoms increases, the electron-withdrawing effect increases.
4. Therefore, ${\text{Cl}}_3\text{CCOOH}$ is the most acidic and ${\text{CH}}_3\text{COOH}$ is the least acidic.
5. Hence the answer is (A).