The freezing point depression constant for water is `-1.86^(@)Cm^(-1).`if `5.00g Na_(2)SO_(4)`is dissolved in `45.0gH_(2)O`,the freezing point is changed by `-3.82^(@)C`,Calculate the van't Hoff factor for `Na_(2)SO_(4)`

Options

A. `2.05`
B. `2.63`
C. `3.11`
D. `0.83`

Answer

B

Explanation

`K_(3)[Fe(CN)_(6)]` dissociates as
`K_(3)[Fe(CN)_(6)]hArr 3K^(+)+[Fe(CN)_(6)]^(3-)`
For electrolytes
`Delta T_(f)=k_(f)xxixx(W_(2))/(m)xx(1000)/(W_(1))`
`=1.86xx4xx(0.1)/(329)xx(1000)/(100)=2.3xx10^(-2)`
`T_(f)=-2.3xx10^(-2).^(@)C`