$N a_{2} S O_{4}(s) \rightarrow 2 N a^{+}+S O_{4}$
hence van's hoff factor $i=3$
Now $\Delta T_{f}=i k_{f} \cdot m=3 \times 1.86 \times 0.01$
$=0.0558 \,K$
${K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ & ${CuSO}_4$
SideX $SPM$ Side $\mathrm{Y}$ Due to osmosis :