The freezing point depression constant for water is `1.86^(@)K Kgmol^(-1)`. If `5.00g Na_(2)SO_(4)` is dissolved in `45.0 g H_(2)O`, the freezing point is charged 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. `0.381`

Answer

B

Explanation

`K_(f) = -186 . ^(@)C mol^(-1)`
`DeltaT_(r ) = I xx K_(f) m `
`3.82 = I xx 1.86 xx (5 xx 1000)/(142 xx 45)`
i= 2.63