Chemistry - Liquid Solution Question with Solution | TestHub

The depression in freezing point is given by $\Delta T_f=i\times K_f\times m$.

For complete dissociation, the van't Hoff factor $i$ is equal to the number of ions produced per formula unit.

For $0.2$ m Potassium chloride (KCl): $i=2$, $i\times m=2\times 0.2=0.4$

For $0.1$ m Sodium chloride (NaCl): $i=2$, $i\times m=2\times 0.1=0.2$

For $0.05$ m Aluminium phosphate (AlPO${}_4$): $i=2$, $i\times m=2\times 0.05=0.1$

For $0.15$ m Magnesium sulphate (MgSO${}_4$): $i=2$, $i\times m=2\times 0.15=0.3$

Since $0.05$ m Aluminium phosphate has the minimum value of $i\times m$, it exhibits the minimum freezing point depression.

Answer: $0.05$ m Aluminium phosphate