Question

In a 0.2 molal aqueous solution of a weak acid HX the degree of ionization is 0.3 Taking `K_(f)` for water as 1.85, the freezing point of the solution will be nearst to
A. `-0.360^(@)C`
B. `0.260^@)C`
C. `+0.480^(@)C`
D. `0.480^(@)C`

Answer 1

Correct Answer - d
`alpha=(i-1)/(n-1)or 0.3=(i-1)/(2-1)`
i=1.3.
`DeltaT_(f)=iK_(f)m`
`=1.3xx(1.85 K kg mol^(-1))xx(0.2 mol kg^(-1))`
=0.480 K.
f.p. of solution = 0-0.480 K.
`=-0.480K=-0480^(@)C`.