Question

The solubility of iodine in water increases in the presence of.

• A. Alcohol
• B. Chloroform
• C. Sodium hydroxide
• D. Potassium iodide

Answer 1

Answer: (D)

Potassium iodide

Answer 2

Iodine has the least affinity for water and is only slightly soluble in it. However, it dissolves in 10% aq. solution of KI due to the formation of a complex ion i.e. $2NaCl + 2H_{2}O \rightarrow 2NaOH + \underset{(\text{anode})}{Cl_{2}} + \underset{(\text{cathode})}{H_{2}}$.

$I_{2} + KI$ ⇌$KI_{3}$ or $I_{2} + I^{-}$ ⇌ $I_{3}^{-}$ (complex ion).