The depression in freezing point of benzene is `0.45^(@)C` when 0.2 g of acetic acid is added to 20 g of benzene. If acetic acid associates to form a dimer in benzene, the percentage association of acetic acid in benzene will be
(`K_(f)` for benzene `=5.12K kg mol^(-1)`)

Options

A. `80.4%`
B. `74.6%`
C. `94.6%`
D. `64.6%`

Answer

C

Explanation

`underset(1-alpha)(2CH_(3)COOH)hArrunderset(alpha//2)((CH_(3)COOH)_(2))`
`i=1-(alpha)/2`
`DeltaT_(f)=i.K_(f)xxm`
`0.45=ixx5.12xx(0.2xx1000)/(60xx20)`
`i=0.527=1-(alpha)/2impliesalpha=0.946`
or `94.6%`