Question

Which of the following will have highest boiling point?

• A. 1% glucose in water
• B. 1% sucrose in water
• C. 1% NaCl in water
• D. 1% urea in water

Hint:

Electrolytes raise boiling point more than nonelectrolytes of the same molality due to a larger van’t Hoff factor.

Answer 1

The Correct Option is C

Step 1: Use colligative property (boiling point elevation).
Boiling point elevation \(\Delta T_b = i\,K_b\,m\) depends on van’t Hoff factor \(i\) (number of particles).
Step 2: Compare \(i\) for solutes.
Glucose, sucrose, urea are non-electrolytes \(\Rightarrow i \approx 1\).
NaCl dissociates into Na\(^+\)+Cl\(^-\) \(\Rightarrow i \approx 2\).
Step 3: Conclusion.
Greater \(i\) gives larger \(\Delta T_b\). Hence 1% NaCl(aq) has the highest boiling point.