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. 0.381
B. 2.05
C. 2.63
D. 3.11

Answer

C

Explanation

`DeltaT_(f)=i xxK_(f)xxm =i xxK_(f)xx(w_(2))/(M_(2))xx(1)/(w_(1))xx1000`
`3.82=ixx1.86xx(5)/(142)xx(1)/(45)xx1000`
`" "("Molar mass of "Na_(2)SO_(4)=142)`
`"or "i=2.62`