The freezing point of benzene decreases by ${0.45}^{°} C$ on adding $0.2 g$ of acetic acid to $20 g$ of benzene. If acetic acid associates to form a dimer in benzene, then what is the percentage association of acetic acid in benzene?
$(K_{f} for benzene = 5 .12 K kg {mol}^{- 1})$

Question

The freezing point of benzene decreases by ${0.45}^{°} C$ on adding $0.2 g$ of acetic acid to $20 g$ of benzene. If acetic acid associates to form a dimer in benzene, then what is the percentage association of acetic acid in benzene?

$(K_{f} for benzene = 5 .12 K kg {mol}^{- 1})$

TestHub · Accepted Answer

2 CH 3 COOH ⇌ CH 3 COOH 2 1 - α α 2 i = 1 - α 2 ΔT f = i × K f × m 0 .45 = i × 5 .12 × 0 .2 × 1000 60 × 20 i = 0 .527 = 1 - α 2 ⇒ α = 0 .946 or 94 . 6 %

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