Question

The vapour pressure of water at room temperature is 23.8 mm Hg. The vapour pressure of an aqueous solution of sucrose with mole fraction 0.1 is equal to

• A. 2.39 mm Hg
• B. 2.42 mm Hg
• C. 21.42 mm Hg
• D. 21.44 mm Hg

Answer 1

Answer: (C)

21.42 mm Hg

Answer 2

The correct answer is Option C) 21.42 mm Hg

Lowering of vapor pressure = ΔP=Po−Ps

Here, The vapor pressure of water = Po=23.8mmHg
The vapor pressure of solution = Ps

Now, the equation can be written as, (Po−Ps) / Po=ixB

Here, i = Van't Hoff factor; for sucrose i= 1

xB= mole fraction of sucrose

⇒ (23.8−Ps) / 23.8 = 1 x 0.1

Ps = 21.42 mm Hg

The vapour pressure of water at room temperature is 23.8 mm Hg. The vapour pressure of an aqueous solution of sucrose with a mole fraction of 0.1 is equal to 21.42 mm of Hg.

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