The freezing point depression constant for water is -1.86^° C m^-1. If 5.00 g Na_2 SO_4 is dissolved in 45.0 g H_2 O, the freezing point is changed…

The freezing point depression constant for water is $\displaystyle -1.86{ }^{\circ} \mathrm{C} m^{-1}$. If $\displaystyle 5.00 \mathrm{~g} \mathrm{Na}_2 \mathrm{SO}_4$ is dissolved in $\displaystyle 45.0 \mathrm{~g} \mathrm{H}_2 \mathrm{O}$, the freezing point is changed by $\displaystyle -3.82^{\circ} \mathrm{C}$. Calculate the van't Hoff factor for $\displaystyle \mathrm{Na}_2 \mathrm{SO}_4$.