The freezing point of benzene decreases by 0.45°C when 0.2g of acetic acid is added to 20g of benzene. If acetic acid associates to form a dimer in benzene, percentage association of acetic acid in benzene will be: (Kffor benzene= `5.12K "kg mol"^(-1)`)

Options

A. 0.946
B. `64.6%`
C. `80.4%`
D. `74.6%`

Answer

A

Explanation

`DeltaT_(f) = i xx m xx k_(f)`
`0.45 = i xx (0.2 xx 1000)/(60 xx 20) xx 5.12`
`i = 0.527 = 1 - alpha + alpha/n` for association
`0.527 = 1- alpha + alpha/2 =1 - alpha/2`