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

`Delta T-(f) = i xx K_(f) xx (W_(2) xx 1000)/(M_(2) xx W_(1)(g))`
Given `: Delta T_(f) = 3.82, K_(f) = 1.86`
`W_(2) = 5, M_(2) = 142, W_(1) = 45`
`i=(3.82 xx 142 xx 45)/(1.86 xx 5 xx 1000)=2.63`