Question

When mercuric lodide is added to the aqueseous solution of potassium iodide?

• A. The boiling point does not change
• B. Freezing point is raised
• C. The freezing point is lowered
• D. Freezing point does not change

Answer 1

The correct option is B Freezing point is raised

Freezing point of the solution increase because there is association of ion which will decrease the number of ions in the solution as a result of which Van't Hoff factor $\left(i\right)$ will decrease as $n$ decrease from $5$ to $3$. Freezing point depression when a solute is added to a solvent is given by $\Delta T=iKpm$. As $i$ decreases, so which means $\Delta T$ is less now. Hence, less depression in freezing point which means Higher freezing point.

$2KI+Hg{I}_2⟶K_2\left[Hg{I}_4\right]$