Q. 145.0( 5 Votes )

# Which of the following statements is false?

A. Two different solutions of sucrose of same molality prepared in different solvents will have the same depression in freezing point.

B. The osmotic pressure of a solution is given by the equation II = CRT

(where C is the molarity of the solution).

C. Decreasing order of osmotic pressure for 0.01 M aqueous solutions of barium chloride, potassium chloride, acetic acid and sucrose is

BaCl_{2} > KCl > CH_{3}COOH > sucrose.

D. According to Raoult’s law, the vapour pressure exerted by a volatile component of a solution is directly proportional to its mole fraction in the solution.

Answer :

Depression in freezing point = i × m × K_{f}

Now, i = van’t Hoff factor, m is the molality and K_{f} is the freezing constant of the solvent.

Now K_{f} is the property of the solvent and is different for different solvent.

Two different solutions of sucrose of the same molality prepared in different solvents will have different depression in freezing point.

Thus, statement (i) is false.

At a given temperature osmotic pressure is given by a formula i.e.

Where is the osmotic pressure, is the van’t Hoff factor, M is the molar concentration, R is the universal gas constant and T is the temperature.

Thus, statement (ii) is correct.

When the concentration of the solute is same osmotic pressure depends on the van’t Hoff factor.

Van’t Hoff factor for BaCl_{2} is 3, for KCl is 2, for CH_{3}COOH is 2 and sucrose it is 1.

Since KCl is ionic it will completely dissolve in the solution its osmotic pressure is greater than that of CH_{3}COOH.

Thus statement (iii) is also correct.

According to Raoult’s law, the partial vapor pressure of each component in the solution is directly proportional to its mole fraction.

Thus, for a component C in a solution

Where P_{C} is the partial pressure of component C and x_{c} is a mole fraction of C in a solution.

Thus statement (iv) is also correct.

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Match the laws given in Column I with expressions given in Column II.