If the elevation in boiling point of a solution of non-volatile, non-electrolytic and non-associating solute in a solvent ( `K_(b)=x "K kg mol"^(-1)` ) is y K, then the depression in freezing point of the same concentration would be ( `K_(f)` of the solvent `= z "K kg mol"^(-1)`)

Options

A. `(2 x z)/(y)`
B. `(yz)/(2)`
C. `(xz)/(y)`
D. `(xz)/(2y)`

Answer

B

Explanation

`DeltaT_(b)=K_(b)xxm` or `y=x xx m` ...(i)
`DeltaT_(f)=K_(f)xxm` or `DeltaT_(f)=z xx m` (ii)
Since m is same, dividing eq. (ii) by eq. (i)
`(DeltaT_(f))/(y)=z/x` or `Delta_(f)=(yz)/(x)`