Question

The boiling point of a glucose solution containing 12 g of glucose in 100 g of water is 100. $34^\circ C$ . Boiling point of water is $100^\circ $ C. The molal elevation constant of water is

• A. 0.51 $^\circ $ C/Molal
• B. 51 $^\circ $ C/Molal
• C. 5.1 $^\circ $ C/Molal
• D. None of these

Answer 1

Answer: (A)

$\Delta T_{b}=100.34-100=0.34^\circ C$
$\Delta T_{b}=\frac{k_{b} \times w_{2} \times 1000}{M_{2} \times w_{1}}$
$k_{b}=\frac{\Delta T_{b} \times M_{2} \times w_{1}}{w_{2} \times 1000}$
$k_{b}=\frac{0.34 \times 180 \times 100}{12 \times 1000}=0.51$