A solution of urea in water has boiling point of `100.15^(@)C`. Calculate the freezing point of the same solution if `K_(f)` and `K_(b)` for water are `1.87 K kg mol^(-1)` and `0.52 K kg mol^(-1)`, respectively.

Options

A. `-0.54^(@)C`
B. `-0.44^(@)C`
C. `-0.64^(@)C`
D. `-0.34^(@)C`

Answer

A

Explanation

`DeltaT_(b)=(100.15-100)=0.15^(@)C`
we know that ,`DeltaT= "molarity" xxK_(b)`
Molarity =`DeltaT_(b)/(K_(b))=(0.15)/(0.52)=0.2884`
`DeltaT_(f)= "molarity" xxk_(f)`
`= 0.2884xx1.87=0.54^(@)C`
Thus , the freezing point the solution
`=-0.54^(@)C`