Question

Which from following solutions in water on complete dissociation exhibits minimum freezing point depression?

• A. \(0.2\) m Potassium chloride
• B. \(0.1\) m Sodium chloride
• C. \(0.05\) m Aluminium phosphate
• D. \(0.15\) m Magnesium sulphate

Hint:

Compare i times m for each solution; the smallest value gives the smallest depression.

Answer 1

The Correct Option is C

Step 1: Approach:
Since the solvent is the same, rank solutions by the total molal concentration of particles.

Step 2: Count particles:
Every salt here splits into two ions (1:1 or 3:3 charge types). So particle molality is just twice the formula molality: 0.4, 0.2, 0.1, 0.3.

Step 3: Pick the least:
The lowest particle molality is 0.1, belonging to the 0.05 m aluminium phosphate solution, so it has the least depression and the highest freezing point.

Final Answer:
Option (C) has the minimum freezing point depression. \[ \boxed{\text{0.05 m aluminium phosphate (C)}} \]