Arrange the following solutions according to decreasing order of osmotic pressure under similar condition of temperature and assuming complete dissociation A. 0.2 m KCl B. 0.3 m MgSO 4 C. 0.1 m BaCl

Question

Arrange the following solutions according to decreasing order of osmotic pressure under similar condition of temperature and assuming complete dissociation A. 0.2 m KCl B. 0.3 m MgSO 4 ​ C. 0.1 m BaCl 2 ​ D. 0.5 m Al 2 ​ ( SO 4 ​ ) 3 ​

TestHub · Accepted Answer

Osmotic pressure is a colligative property, which depends on the total number of solute particles in the solution. For electrolytes, $π \propto i \times m$ , where $i$ is the van't Hoff factor and $m$ is the molality.

For complete dissociation:
A. $KCl \to K^{+} + Cl^{-}$ , $i = 2$ . Effective concentration $= 2 \times 0.2 = 0.4 m$
B. $MgSO_{4} \to Mg^{2 +} + SO_{4}^{2 -}$ , $i = 2$ . Effective concentration $= 2 \times 0.3 = 0.6 m$
C. $BaCl_{2} \to Ba^{2 +} + 2 Cl^{-}$ , $i = 3$ . Effective concentration $= 3 \times 0.1 = 0.3 m$
D. $Al_{2} (SO_{4})_{3} \to 2 Al^{3 +} + 3 SO_{4}^{2 -}$ , $i = 5$ . Effective concentration $= 5 \times 0.5 = 2.5 m$

Comparing the effective concentrations, the decreasing order of osmotic pressure is $D > B > A > C$ .

Answer: $D > B > A > C$

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