Solutions and Colligative Properties - Result Question 25-2
25. When mercuric iodide is added to the aqueous solution of potassium iodide
(1987, 2M)
(a) freezing point is raised
(b) freezing point is lowered
(c) freezing point does not change
(d) boiling point does not change
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Answer:
Correct Answer: 25. (a)
Solution:
Addition of $\mathrm{HgI}_2$ to $KI$ solution establishes the following equilibrium :
$ \mathrm{HgI}_2+2 \mathrm{KI} \rightleftharpoons \mathrm{K}_2\left[\mathrm{HgI}_4\right] $
The above equilibrium decreases the number of ions ( $4$ ions on left side of reactions becomes three ions on right side), hence rises the freezing point.
BETA
