Which of the following aqueous solutions will exhibit highest boiling point?

Question

Which of the following aqueous solutions will exhibit highest boiling point?

1. A. 0.01M Urea
2. B. 0.01M KNO3
3. C. 0.01M Na2SO4 (Correct answer)
4. D. 0.015M C6H12O6

Correct Answer

Option C — 0.01M Na2SO4

Detailed Solution & Explanation

The correct answer is 0.01M Na$_2$SO$_4$.

Key Points

• Elevation of boiling point $\Delta T_b=i\,K_b\,m$, so it depends on the product $i\times m$ (van't Hoff factor $\times$ molality).
• Urea: $i\times m=1\times0.01=0.01$; KNO$_3$: $2\times0.01=0.02$; Na$_2$SO$_4$: $3\times0.01=0.03$; glucose: $1\times0.015=0.015$.
• Na$_2$SO$_4$ has the largest $i\times m$, hence the highest boiling point.