Short Answer TypeThe reaction
is at equilibrium, 
formed is absorbed in sulphuric acid, what happens to the equilibrium?
In a gaseous system at equilibrium 
3 mole of inert gas is pumped into the vessel at constant pressure. What will be its effect on equilibrium?
Long Answer TypeShort Answer TypeWhat is the effect of pressure on the solubility of a gas in a liquid?
Or
State Henry's Law.
A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
(i) What is the initial effect of the change on vapour pressure?
(ii) How do rates of evaporation and condensation change initially?
(iii) What happens when equilibrium is restored finally and what will be the final vapour pressure?
Long Answer Type(i) In case of liquid 
gas equilibrium, the vapour pressure of the liquid becomes constant at a given temperature.
(ii) In case of solid 
solution equilibrium, the concentration of solute in solution becomes constant at a given temperature.
(iii) In the case of gas 
solution equilibrium, the pressure of the gas above liquid becomes constant at a given temperature.
(iv) In the case of solid 
liquid equilibrium, there is only one temperature (melting point) at which two phases can co-exist i.e. temperature remains constant at a given pressure.
Hence the common characteristics of physical equilibrium are:
1. Equilibrium can be established only in case of a closed system.
2. The equilibrium is dynamic in nature i.e. the process does not stop after the establishment of equilibrium but the rate of the forward reaction becomes equal to the rate of backward reaction.
3. The measurable properties of the system such as melting point, boiling point, vapour pressure and solubility remain constant since the concentration of the substances remains constant.
4. When equilibrium is attained there exists an expression involving the concentration of reacting substances which acquire a constant value at a given temperature.
5. In the case of a gas dissolving in a liquid, the increase of pressure always increases the solubility of the gas in the liquid.
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