Question

If 10 g each of glucose, urea and sucrose is dissolved in 250 mL of water having osmotic pressure π₁, π₂ and π₃ respectively, the decreasing order of osmotic pressure of these solutions is ________.

Options

• π₁ > π₂ > π₃

• π₂ > π₁ > π₃

• π₂ > π₃ > π₁

• π₃ > π₁ > π₂

Answer 1

If 10 g each of glucose, urea and sucrose is dissolved in 250 mL of water having osmotic pressure π₁, π₂ and π₃ respectively, the decreasing order of osmotic pressure of these solutions is π₂ > π₁ > π₃.

Explanation:

Molar mass of glucose = C₆H₁₂O₆ = 180 g Moles of glucose = `10/180` = 0.056

Molar mass of urea = CO(NH₂)₂ = 60 g

Moles of urea = `10/60` = 0.167

Molar mass of sucrose= C₁₂H₂₂O₁₁ = 342

Moles of Sucrose = `10/342` = 0.029

∵ No. of moles ∝ no. of particles

∴ Decreasing order of osmotic pressure of solution is

`[("Urea"),((pi_2))] > [("glucose"),((pi_1))] > [("sucrose"),((pi_3))]`