Question

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

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

Answer 1

The correct option is A Freezing point is raised

When mercuric iodide is added to the aq. solution of $KI$, the freezing point of the given solution increases. Mercuric iodide will react with $KI$ to form dipotassium tetraiodomercury as :
$2KI+Hg{I}_2\to K_2\left[Hg{I}_4\right]$
Since Number of ions decreases, hence van't Hoff factor ($i$) will decrease and freezing point of the solution will increase.