Question

3. Mono chloroacetic acid is stronger than propionic acid​

Answer 1

Answer:

Why is monochloroacetic acid a stronger acid than acetic acid?

Well, consider the defining equilibria, for which we will supply thermodynamic data…

H3C−C(=O)OH(aq)+H2O(l)⇌H3C−C(=O)O−+H3O+

…for which pKa=4.76

ClH2C−C(=O)OH(aq)+H2O(l)⇌ClH2C−C(=O)O−+H3O+

…for which pKa=2.85

Cl3C−C(=O)OH(aq)+H2O(l)⇌Cl3C−C(=O)O−+H3O+

…for which pKa=0.70

The enhanced acidities of the halo-acid is well-known to be an entropy effect. The charge density of chloroacetate is MUCH less than of acetate ion, and thus the second reaction is STRONGLY FAVOURED by entropy… i.e. chloroacetate is LESS efficiently solvated by the solvent water molecules…and this effect is magnified with respect to trichloroacetate ion…