Phenol associates in benzene to certain extent to form a dimer. A solution containing `20 xx 10^(-3) kg` of phenol in `1.0 kg` of benzene hs its freezing point depressed by `0.69 K`. Calculate the fraction of phenol that has dimerized. (`K_(f)` for benzene is `5.12 K kg mol^(-1)`).

Options

A. `746.24`
B. `646.24`
C. `846.24`
D. `546.23`

Answer

A

Explanation

`a=0.7`
`n_(r)=(1+2alpha)n_(1)+n_(2)`
`=2.4n_(1)+n_(2)`
`n_(1)=(7)/(164)`
`n_(2)=(100)/(18)`
`P_(s)=(760)(100/18)/(2.4xx(7)/(164)+(100)/(8))`
`P_(s)=746.24mmHg`