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 :
freezing point is raised.
Solution :
Added $$Hg{I_2}$$ 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 particles decreases and so $$\Delta {T_f}$$ increases.
[ NOTE : : Depression in freezing point is a colligative property ]