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Question
Give two points to explain why vapour pressure of solvent is lowered by dissolving nonvolatile solute into it.
Solution
- Vapour pressure of a liquid depends on the ease with which the molecules escape from the surface of liquid. When nonvolatile solute is dissolved in a solvent, some of the surface molecules of solvent are replaced by nonvolatile solute molecules. These solute molecules do not contribute to vapour above the solution.
- Thus, the number of solvent molecules available for vaporization per unit surface area of a solution is less than the number at the surface of pure solvent. As a result the solvent molecules at the surface of solution vaporize at a slower rate than pure solvent. This results in lowering of vapour pressure.
RELATED QUESTIONS
Answer the following.
Why vapour pressure of a solvent is lowered by dissolving a nonvolatile solute into it?
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Write the expression for relative lowering of vapour pressure.
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Which of the following is NOT a colligative property?
The vapour pressure of solvent decreases by 1 O mm Hg, if mole fraction of non-volatile solute is 0.2. Calculate vapour pressure of solvent.
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Relative lowering of vapour pressure of a solution of non-volatile solute depend only on ____________.
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Which of the following is CORRECT statement?
At a constant volume, a quantity of an ideal gas has a pressure of 700 mm Hg at 300 K. At what pressure, the temperature will be halved?
According to Raoult's law, relative lowering of vapour pressure for a solution containing a nonvolatile solute is equal to ____________.
Which of the following is INCORRECT expression in terms of vapour pressure of pure solvent `("P"_1^0)` and that of solution (P)?
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Identify the correct statement from the following:
38.4 g of unknown substance (molar mass 384 g mol-1) and 116 g of acetone is used to prepare a solution at 313 K. If vapour pressure of pure acetone (molar mass 58 g mol-1) is 0.842 atmosphere, what is the vapour pressure of solution?
12 g of a nonvolatile solute dissolved in 108 g of water produces the relative lowering of vapour pressure of 0.1. The molecular mass of the solute is ______.
Which of the following solutions will have the maximum lowering of vapour pressure at 300 K?
State and explain Raoult's law for the solution of non-volatile solutes.
