Question

Elevation in boiling point of a molar (1M) glucose solution $(d=1.2\,g\,mL^{-1})$ is

• A. $1.34\,K_{b}$
• B. $0.98\,K_{b}$
• C. $2.40\,K_{b}$
• D. $K_{b}$

Answer 1

Answer: (B)

Molarity $=1\,M=1\,mol\,L^{-1}$
1000 mL of solution has glucose = 180 g
$(1000 \times 1.2)\,g$ of solution has glucose = 180 g
$\therefore $ Solute $(w_{1})=180\,g$
Solution $= 1200\, g$
Solvent, $H_{2}O (w_{2})=120-180=1020\,g$
$\therefore \Delta T_{b}=\frac{1000K_{b}w_{1}}{m_{1}w_{2}}$
$=\frac{1000\times K_{b}\times180}{180\times1020}$
$=0.98K_{b}$