2021 SolutionsColligative Properties – Osmotic Pressure Medium Question 17 of 62 in Solutions

The following solutions were prepared by dissolving 10 g of glucose ($C_6H_{12}O_6$) in 250 ml of water ($P_1$), 10 g of urea ($CH_4N_2O$) in 250 ml of water ($P_2$) and 10 g of sucrose ($C_{12}H_{22}O_{11}$) in 250 ml of water ($P_3$). The right option for the decreasing order of osmotic pressure of these solutions is:

A $P_1>P_2>P_3$
B $P_2>P_3>P_1$
C $P_3>P_1>P_2$
D $P_2>P_1>P_3$

The answer is D.

Solution

$\pi = iCRT$ with i = 1 for all three (non-electrolytes) and the same volume, so $\pi \propto \frac{mass}{molar\ mass}$ $P_1 = \frac{10}{180}RT$ (glucose), $P_2 = \frac{10}{60}RT$ (urea), $P_3 = \frac{10}{342}RT$ (sucrose) So $P_2 > P_1 > P_3$

Concept osmotic pressure vs molar mass

Solutions in past papers

62 questions from this chapter have appeared across 25 exam years.