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

Options

A. `2.63`
B. `3.11`
C. `0.381`
D. `2.05`

Answer

A

Explanation

According to depression in freezing point.
`Delta T_(f)=I xx K_(f).m`
where, `K_(f)` = cryoscopic constant
or `i=(Delta T_(f)xxW_("solvent"))/(K_(f)xx n_("solute")xx1000)`
`=(3.82xx45)/(1.86xx((5)/(142))xx1000)=2.63`