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

Solution & Explanation

\textbf{Answer:} (A) 0.01 M \ce{Na2SO4} \textbf{Solution:} Elevation of boiling point is colligative: $\Delta T_b = i K_b m$, so the highest boiling point corresponds to the largest effective particle concentration $i \times m$. \ce{Na2SO4} ($i = 3$, $m = 0.01$): $i m = 0.03$. \ce{KNO3} ($i = 2$, $m = 0.01$): $i m = 0.02$. Glucose \ce{C6H12O6} ($i = 1$, $m = 0.015$): $i m = 0.015$. Urea ($i = 1$, $m = 0.01$): $i m = 0.01$. The largest value (0.03) is for 0.01 M \ce{Na2SO4}, which therefore has the highest boiling point.