91Ó°ÊÓ

Electron-withdrawing groups increase the acidity of carboxylic acids.

More the number of electron-withdrawing groups on an acid molecule, higher is its acidity.

${\mathbf{pK}}_{\mathbf{a}}$ is inversely related to the acidity of a compound, i.e., a strong acid has lower ${\mathbf{pK}}_{\mathbf{a}}$, while a weak acid has higher ${\mathbf{pK}}_{\mathbf{a}}$.

Among the halogen atoms, fluorine is the most electronegative (highly electron-withdrawing) and hence the carboxylic acids containing fluorine atoms are more acidic, followed by the one containing bromine and then the one containing iodine.

Higher the number of electron-withdrawing groups, higher is the acidity.

Therefore, the order of acidity of the given acids are:

${\mathrm{CF}}_3\mathrm{COOH}>{\mathrm{F}}_2\mathrm{CHCOOH}>{\mathrm{FCH}}_2\mathrm{COOH}>{\mathrm{BrCH}}_2\mathrm{COOH}>{\mathrm{ICH}}_2\mathrm{COOH}$

Therefore, the of the given acids are:

${\mathrm{CF}}_3\mathrm{COOH}\left({\mathrm{pK}}_{\mathrm{a}}=0.28\right),{\mathrm{F}}_2\mathrm{CHCOOH}\left({\mathrm{pK}}_{\mathrm{a}}=1.24\right),{\mathrm{FCH}}_2\mathrm{COOH}\left({\mathrm{pK}}_{\mathrm{a}}=2.66\right),{\mathrm{BrCH}}_2\mathrm{COOH}\left({\mathrm{pK}}_{\mathrm{a}}=2.86\right),{\mathrm{ICH}}_2\mathrm{COOH}\left({\mathrm{pK}}_{\mathrm{a}}=3.12\right)$