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

Options

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

Answer

D

Explanation

`Delta T_(f)=0.45`
`m=(((0.2)/(60))xx1000)/(20)=(1)/(6)`
`K_(f)=5.12` K kg / mol
`i=1+((1)/(n)-1)x " " (n=2)`
`= 1-(x)/(2)`
`Now, Delta T_(f)=iK_(f)m`
`0.45=(1-(x)/(2))(5.12)((1)/(6))`
x = 0.94
`therefore` Percentage of `~~ 94%`