question_answer 43)

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:

Fluorine, being the most electronegative, has the strongest electron withdrawing inductive effect (-I effect). Consequently, trifluoroacetic acid is the strongest acid while acetic acid is the weakest acid. Hence, trifluoroacetic acid ionizes most while acetic acid ionizes least. More the number of ions produced, more is the depression in freezing point. Thus, the depression in freezing point is maximum for the trifluoroacetic acid and minimum for acetic acid. The depression in freezing points are in the order: Acetic acid < trichloroacetic acid < trifluoracetic acid.