# When mercuric iodide is added to an aqueous solution of potassium iodide the

$\begin{array}{1 1} \text{freezing point is raised} \\\text{freezing point is lowered } \\\text{freezing point does not change}\\\text{boiling point does not change} \end{array}$

Answer : freezing point is raised.
The reaction is $Hgl_2 +2Kl \to K_2Hgl_4$.
Hence $2K^{+}$ and $2L^{-1}$ are replaced by $2K^{+}$ and $Hgl_4^{2-}$.
There is a decrease in the number of species in the solution .
The value of $\Delta T_r$ decreases , hence , freezing point is raised.