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Standard XII
Chemistry
Raoult's Law
Question

Which of the following statements regarding a liquid is not correct?
  1. The vapour pressure of a liquid increases with increase in temperature.
  2. The vapour pressure of a liquid decreases in the presence of a non-volatile impurity.
  3. The vapour pressure increases with decrease in temperature.
  4. At the normal boiling point, the vapour pressure of a liquid is 1 atm.

A
The vapour pressure of a liquid increases with increase in temperature.
B
The vapour pressure of a liquid decreases in the presence of a non-volatile impurity.
C
The vapour pressure increases with decrease in temperature.
D
At the normal boiling point, the vapour pressure of a liquid is 1 atm.
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Solution
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When a liquid is heated, it starts evaporating. So, more pressure is exerted because more molecules converts to vapour state.

So, the vapour pressure increases with the increase in temperature.

Option C is correct.

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Similar Questions
Q1
The following are some statements about vapour pressure.
I. Vapour pressure of a solution increases with increase in temperature.
II. Liquids with high vapour pressure even at ordinary temperatures are volatile liquids.
III. The temperature at which vapour pressure of solution is equal to atmospheric pressure is called boiling point.
IV. When a non-volatile solute is dissolved in a volatile solvent, its vapour pressure decreases.
Which of the above is/are correct?

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Q2

Vapour pressure of a liquid decreases with increase in:


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Q3
Comprehension # 2
Following passage explains the effect of temperature on the vapour pressure of the liquid.

Effect of temperature on vapour pressure
The quantity of heat required to evaporate a given liquid at constant temperature is defined as the heat of vaporisation. Variation of vapour pressure with temperature is given by,

Clausius-Clapeyron equation.

logeP=−ΔHvapRT+logeA

A liquid is said to be at its boiling temperature if its vapour pressure is equal to external pressure. Therefore, the boiling point of water in particular and of liquids in general decreases as an altitude of a place increases where the external pressure is less than 1atmosphere (normal b.p. of water is 373.15K at 1atmosphere)

On top of mount everest, for example, where the atmospheric pressure is only about 260mmHg, water boils at approximately 71∘C. Conversely, if the external pressure on a liquid is greater than 1atm, the vapour pressure necessary for boiling than normal boiling is reached later, and the liquid boils at a temperature greater than the normal boiling point.

Clausius-Clapeyron equation can be written in the following form:

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Q4

Based on the statements given here choose the correct answer.
(1) Boiling point of a liquid increases with increase in temperature.
(2) The volume of liquids increases on boiling and the vaporisation curve shows the variation of the boiling point of a liquid with pressure and expands the equilibrium state between liquid and vapour phase.


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Q5
The normal boiling point of a liquid is that temperature at which vapour pressure of the liquid is equal to:
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