Mass of glucose $\left(\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6\right)$ required to be dissolved to prepare…
Mass of glucose $\left(\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6\right)$ required to be dissolved to prepare one litre of its solution which is isotonic with $15 \mathrm{~g} \mathrm{~L}^{-1}$ solution of urea $\left(\mathrm{NH}_3 \mathrm{CONH}_2\right)$ is (Given: Molar mass in $\mathrm{g} \mathrm{mol}{ }^{-1} \mathrm{C}: 12, \mathrm{H}: 1, \mathrm{O}: 16, \mathrm{~N}: 14$ )
55 g
15 g
30 g
45 g
Solution
For isotonic solutions [osmotic pressure must be equal]
$\pi_1=\pi_2$
$\mathrm{C}_1 \mathrm{RT}=\mathrm{C}_2 \mathrm{RT}$
$\mathrm{C}_1=\mathrm{C}_2$
$\frac{\mathrm{m}}{180 \times 1}=\frac{15}{60 \times 1} \quad(\mathrm{~m}$ is the mass of glucose)
$m=\frac{180}{4}=45 \mathrm{~g}$