Question

Which of the following solution has the highest boiling point?

• A. 1% glucose
• B. 1% NaCI
• C. 1% sucrose
• D. 1% $ CaCl_{2} $

Answer 1

Answer: (B)

Elevation in boiling point is colligative property, it depends upon number of ions or molecules or particles.
Glucose and sucrose does not dissociate
so $n=1$ for these solutions while for $N a C l, n=2$
and for $C a C l, n=3. 1\%$
solution means $100 \,g$ solution contains $1 \,g$ solute
(glucose or $NaCl$ or sucrose or $C a C l). w_{2}=1 \,g, w_{1}$
(solvent) $=99\, g$
$\Delta T_{b}=\frac{i \times k_{b} \times W_{2} \times 1000}{M_{2} \times W_{1}}$
For glucose. $\Delta T_{b}=\frac{1}{180}=0.0056$
(because $k_{b}, w_{2}, w_{1}$ same for all the cases)
For sucrose, $\Delta T_{b}=\frac{1}{342}=0.00292$
For $NaCl , \Delta T_{b}=\frac{2}{58.5}=0.0342$
For $C a C l_{2}$,
$\Delta T_{b}=\frac{3}{111}=0.0270$
Hence $1 \% NaCl$ solution has the highest boiling point.