A solution of urea boils at `100.18^(@)C` at the atmospheric pressure. If `K_(f)` and `K_(b)` for water are `1.86` and `0.512K kg mol^(-1)` respectively, the above solution will freeze at,

Options

A. `- 6.54^(@)C`
B. `6.54^(@)C `
C. ` 0.654^(@)C `
D. `-0.654^(@)C `

Answer

D

Explanation

`m = ( Delta T_(b))/( K_(b)) = ( Delta T_(f))/(K_(f))`
Boiling point of water is `100^(@)C ` and freezing point of water is `0^(@)C `.
`Delta T_(f) =( 0.18 xx 1.86 )/(0.5162) 0.654`
Freezing point of solution is = F.P. of solvent- depression in F.P.
`=0-0.654= - 654^(@)C`