liquids

1. 1
Chapter NO : 04 Liquids And Solids
Chemistry : By Sir Bilal
Talat Yasmin College
Sangla Hill

2. Contents
Vapour pressure
Factors affecting on vapour pressure
Temperature
Intermolecular forces
Summary
Exams Questions
1

3. Vapour Pressure
The pressure exerted by the vapours of liquid in equilibrium with the
liquid at a given temperature is called vapour pressure.
2
Definition
Dynamic Equilibrium :Equilibrium in which Rate of evaporation becomes equal
to rate of condensation.

4. 3
Vapour Pressure
Some Facts About Vapour Pressure
 Vapour pressure of a pure liquid is always more than impure liquids.
 Vapour pressure of liquid is inversely proportional to its boiling point.
 Vapour pressure of liquid is independent the amount of liquid.
 Vapour pressure of liquid is also independent the surface area of liquid.

5. Factors affecting onVapour Pressure
4
Temperature
Increases in temperature increases the vapour pressure of a liquid and vice
versa. It is because at high temperature Kinetic Energy of molecules increases
therefore evaporation increases hence vapour pressure increase.
The vapour pressure of H2O
increases from 4.579torr to
9.209torr from 0 oC to 10 oC
but it increases from 527.8torr
to 760torr from 90 oC to 100 oC
Example

6. 5
Intermolecular Forces
 Stronger the intermolecular forces lower will be the vapour pressure of
a liquid vice versa.
Examples
 At 20 oC H2O with strong intermolecular hydrogen bonding has low vapour
pressure 17 torr than ether 442 torr in which no hydrogen is present.
 Isopentane has the high vapour pressure due to weak London forces while
glycerol has low due to strong hydrogen bonding.
Factors affecting onVapour Pressure

7. 6
Summary

8. 7
Exams Questions
Intermolecular Forces
1. Vapour pressure of a liquid depends upon :
A) Amount of liquid
B) Surface Area
C) Temperature
D) Size of container
2. Vapour Pressure of a substance does not depend upon
A) Temperature
B) Intermolecular forces
C) Surface Area
D) Physical State of matter