Q. 314.0( 18 Votes )
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.
The depression in freezing point of water observed for the same amount of acetic acid, trichloroacetic acid and trifluoroacetic acid increases in the pattern,
Acetic acid< trichloroacetic acid< trifluoroacetic acid.
This is because fluorine is more electronegative than chlorine. So, trifluoracetic acid is a stronger acid in comparison to trichloroacetic acid and acetic acid. And also, acetic acid is the weakest of all.
Explanation: Stronger acid produces more number of ions, therefore it has more ΔTf(depression in freezing point), hence lower freezing point. As the acidic strength increases, the acid gets more and more ionised.
Trifluoracetic acid ionizes to the largest extent. Hence, in this case, trifluoracetic acid being the strongest acid produces more number of ions(extent of ionisation and concentration of ions are more), high ΔTf(depression in freezing point)and lower freezing point and vice versa.
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