Question

Which among the following aqueous solutions has the highest boiling point?

• A. 1% glucose
• B. 1% sucrose
• C. 1% NaCl
• D. 1% CaCl$_2$

Hint:

The boiling point elevation is directly proportional to the van't Hoff factor (i). The more ions a substance dissociates into, the greater the elevation in boiling point.

Answer 1

The Correct Option is D

Step 1: Understand the concept of boiling point elevation.
Boiling point elevation occurs when a solute is added to a solvent, resulting in an increase in the boiling point. The extent of boiling point elevation depends on the number of particles in solution, which is determined by the van't Hoff factor (i).
Step 2: Analyze the van't Hoff factor.
- Glucose and sucrose are non-electrolytes, meaning they do not dissociate into ions in solution. Their van't Hoff factor (i) is 1. - NaCl dissociates into 2 ions (Na$^+$ and Cl$^-$), so its van't Hoff factor (i) is 2. - CaCl$_2$ dissociates into 3 ions (Ca$^{2+}$ and 2 Cl$^-$), so its van't Hoff factor (i) is 3.
Step 3: Apply to the options.
The higher the van't Hoff factor, the higher the number of particles in solution, leading to a greater boiling point elevation. Therefore, the solution with the highest boiling point will be the one with CaCl$_2$, which has the highest van't Hoff factor.
Final Answer: \[ \boxed{1% \text{CaCl}_2} \]