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 nearest to

Options

A. `-0.480^(@)C`
B. `-0.360^(@)C`
C. `-0.260^(@)C`
D. `+0.480^(@)C`

Answer

A

Explanation

`{:(HX hArr,H^(+)+,X^(-)),(1,-,-),(1-0.3,0.3,0.3):}`
`DeltaT_(f) = iK_(f)m = 1.3 xx 1.85 xx 0.2 = 0.48`
`:. T_(f) = (0-48)^(@)C = 0.48^(@)C`