Question

When mercuric iodide is added to the aqueous solution of potassium iodide then:

• A. Freezing point is raised
• B. Freezing point is lowered
• C. Freezing point does not change
• D. Boiling point does not change

Answer 1

The correct option is A Freezing point is raised

When mercuric iodide is added to the aqueous solution of potassium iodide, it forms a complex with $KI$ in the solution as follows:
$2KI+Hg{I}_2\to K_2\left[Hg{I}_4\right]$
As a result number of solute particles decreases.
Since depression of freezing point and elevation of boiling point are colligative properties of a solution, thus freezing point and boiling point of the solution certainly changes and freezing point of the solution is raised as the number of solute particle decreases.