Question

Which has the highest boiling point?

• A. \(0.1\,\text{M } Na_2SO_4\)
• B. \(0.1\,\text{M } C_6H_{12}O_6\) (glucose)
• C. \(0.1\,\text{M } MgCl_2\)
• D. \(0.1\,\text{M } Al(NO_3)_3\)

Hint:

For solutions of equal concentration: \[ \Delta T_b \propto i \] Greater the number of ions produced in solution, higher is the boiling point elevation.

Answer 1

The Correct Option is D

Step 1: Elevation in boiling point is given by: \[ \Delta T_b = i K_b m \] where \(i\) is the van’t Hoff factor.
Step 2: Calculate the van’t Hoff factor for each solution. \[ Na_2SO_4 \rightarrow 2Na^+ + SO_4^{2-} \Rightarrow i = 3 \] \[ C_6H_{12}O_6 \;(\text{non-electrolyte}) \Rightarrow i = 1 \] \[ MgCl_2 \rightarrow Mg^{2+} + 2Cl^- \Rightarrow i = 3 \] \[ Al(NO_3)_3 \rightarrow Al^{3+} + 3NO_3^- \Rightarrow i = 4 \]
Step 3: Since all solutions have the same molarity, the solution with the highest van’t Hoff factor will show the greatest elevation in boiling point.
Step 4: \(Al(NO_3)_3\) has the highest value of \(i = 4\).