Question

The depression in freezing point of water observed for the same amount of acetic acid, trichloroacetic acid and trifluoroacetic acid increases in the order given above. Explain briefly.

Answer 1

When strongly electron withdrawing groups are present on alpha C atom of acetic acid, the acid strength and the degree of dissociation increases. This increases the vant Hoff factor i and the depression in the freezing point. Trifluoroacetic is most acidic because fluorine is most electron withdrawing in nature. Hence, trifluoroacetic acid has maximum depression in the freezing point.