Question

The experimental values of colligative properties of many solutes in solution resembles calculated values of colligative properties.
However in some cases, the experimental values of colligative properties differ widely than those obtained by calculations. Such experimental values of colligative properties are known as abnormal values of colligative properties. The causes for abnormal values of colligative properties are:
(i) Dissociation of solute: It increases the colligative properties.
e.g.: Dissociation of $\text{KCl, NaCl}$ etc. in $H_{2}O$.
(ii) Association of solute: It decreases the colligative properties.
e.g.: Dimerisation of acetic acid in benzene.

One mole of $I_2$ (solid. is added in $1\text{M}$, 1 litre $\text{KI}$ solution. Then,

• A. Osmotic pressure of the solution increases
• B. Freezing point of the solution increases
• C. Relative lowering in the vapour pressure decreases.
• D. There is no change in the boiling point of the solution.

Answer 1

The correct option is D There is no change in the boiling point of the solution.

$KI+I_2\to K{I}_3$

$K{I}_3$ dissociates as $K^{+}and{I}_3^{-}$

so, numbers of ions are same. Hence no change in boiling point of solution.