Question

The solubility of iodine in water increases in the presence of
A. Alcohol
B. Chloroform
C. Sodium hydroxide
D. Potassium iodide

Answer 1

Hint: Solubility of any substance or compound is defined as its power to dissolve in a solvent. As the solubility increases the substance becomes easily dissolvable in any solvent.

Complete Step by Step Solution:
We know that water is a polar solvent. So, it will dissolve an ionic substance more easily than a covalent substance.
Here iodine is a gas and purely covalent compound. It has a covalent bond between two iodine atoms. Thus iodine will not dissolve in water or become less soluble in polar solvent water. It is more dissolve in non polar solvents like ethanol, ethylene etc.
But in presence of potassium iodide the iodine gas form an triodide ion. The triodide ion is ionic in nature and increases the solubility of iodine gas in water.
The reaction is given as follows-
$KI+{{I}_{2}}\rightleftharpoons {{K}^{+}}+I_{3}^{-}$
Thus the correct option is D.

Note: Polar solvents dissolve the polar substance or solute easily and form polar solution. The examples of polar solvents are water, DMF. For example sodium chloride is a polar salt and dissolves in polar solvent water easily. Again non polar solvents dissolve the non polar substance or solute easily and form non polar solution. The examples of non polar solvents are chloroform, carbon tetrachloride etc.