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Identify the statement that is not true:

1. For 0.01 M aqueous solutions of the given substances, the osmotic pressure increases in the order BaCl2 > KCl > CH3COOH > sucrose.
2. The osmotic pressure of a solution is expressed by π = MRT, where M denotes the solution’s molarity.
3. According to Raoult’s law, the vapour pressure of a component above a solution is directly proportional to its mole fraction.
4. Two sucrose solutions having the same molality but made in different solvents will show the same depression in freezing point.

Correct answer: Two sucrose solutions having the same molality but made in different solvents will show the same depression in freezing point.

Solution

Depression of freezing point is dTf = Kf x molality, and Kf differs from solvent to solvent, so equal-molality sucrose solutions in different solvents do NOT show equal dTf. That statement (index 3) is the untrue one; pi = MRT is correct.

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