Question

When mercuric iodide is added to aqueous solution of KI:

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

Answer 1

The correct option is A Freezing point is raised

When mercuric iodide is added to aq.sol. of $KI$ the freezing point of the given solution increases. Mercuric Iodide will react with Potassium Iodide to form dipotassium tetraiodomercury as:

$2KI+Hg{I}_2\to K_2\left[Hg{I}_4\right]$

This will decrease the number of ions in the solution and so Vanthaff factor decreases which depend on the number of particles.