Q93 / 200 · NEET 2024 (Re-NEET) · Chemistry

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 $\mathrm{g} \mathrm{mol}{ }^{-1} \mathrm{C}: 12, \mathrm{H}: 1, \mathrm{O}: 16, \mathrm{~N}: 14$ )

  • A
    55 g
  • B
    15 g
  • C
    30 g
  • Correct answer
    D
    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) $m=\frac{180}{4}=45 \mathrm{~g}$

Hence, the correct answer is option: 'D'.

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