Question

To `500cm^(3)` of water, `3.0 xx 10^(-3) kg` acetic acid is added. If `23%` of acetic acid is dissociated, what will be the depression in freezing point? `K_(f)` and density of water are `1.86 K kg mol^(-1)` and `0.997 g cm^(-3)` respectively.

Answer 1

`Delta T = K_(f) xx "molality" xx(1+alpha)`
For acetic acid: `{:(CH_(3)COOH,hArr,CH_(3)COO^(-)+,H^(+),),(1,,0,0,),(1-alpha,,alpha,alpha,):}`
Given `alpha = 0.23`, Also, molality
`= ("mole of acetic acid")/("weight of water(in kg)")`
`(3 xx 10^(-3) xx 10^(3))/(60 xx (500 xx 0.997)/(10^(3))) = 0.10`
`Delta T = K_(f) xx "molality"(1+alpha)`
`Delta T = 1.86 xx 0.1 xx 1.23 = 0.229`