Chemistry - Liquid Solution Question with Solution | TestHub

The ratio of theoretical molar mass to the experimentally observed molar mass is known as the van 't Hoff factor $i$.

$i=\frac{\text{Theoretical molar mass}}{\text{Observed molar mass}}$

We need to find the solute for which $i=3$. Assuming complete dissociation for the given strong electrolytes:

For $\text{KCl}\to {\text{K}}^{+}+{\text{Cl}}^{-}$, $i=2$

For ${\text{K}}_2{\text{SO}}_4\to 2{\text{K}}^{+}+{\text{SO}}_4^{2-}$, $i=3$

For ${\text{MgSO}}_4\to {\text{Mg}}^{2+}+{\text{SO}}_4^{2-}$, $i=2$

For ${\text{Al}}_2({\text{SO}}_4{)}_3\to 2{\text{Al}}^{3+}+3{\text{SO}}_4^{2-}$, $i=5$

Thus, ${\text{K}}_2{\text{SO}}_4$ has a van 't Hoff factor of $3$.

Answer: ${\text{K}}_2{\text{SO}}_4$