Behaviour of saturated vapour - MeroPaper


Behaviour of saturated vapour

Behaviour of saturated vapour

Saturated vapour pressure of a liquid has following properties.

  1. The Saturated vapour pressure depends on nature of the substance.
  2. The vapour pressure of a liquid depends on its temperature. The saturated vapour pressure increases with rise in temperature and decreases with fall in temperature.
  3. The  vapour pressure is always greater than unsaturated vapour pressure.
  4. It doesnot depend on the volume occoupied by the vapours.
  5. It is dependent of the pressure of vapours of other liquids present. The vapour should not have any chemical reaction.
  6. The total pressure exerted by the vapours of all substances is equal to the sum of the pressure exerted by the vapour of individual substances I.e P=p1+p2+p3
  7. The  vapour doesnt obey the gas law where as unsaturated vapour obey the gas laws.


In the figure Curve, AB shows that pressure increases with a decrease in volume. From A to B the vapour is unsaturated and obeys Boyle’s law. At point B, the vapour is unsaturated and exerts maximum pressure. Beyond B with the decrease in volume, pressure remains constant. From B to C it represents the change from the saturated vapour to the liquid state.

In the Fig curve, AB shows pressure is increased with rising in temperature. A to B vapour is saturated. Beyond B, if Temperature is increased the vapour becomes unsaturated and pressure increases with temperature In BC, The pressure of unsaturated vapour is directly proportional to absolute temperature.



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