If a system at equilibrium is subjected to a change of any one of the factors such as concentration , pressure or temperature, the system adjusts itself in such a way so as to minimise the effect of that change.
Effect of change in concentration on equilibrium:
As we add or remove reactant (or product) the ratio of equilibrium concentratio become 'Q' (reaction quotient) and depending upon.
$Q<K$: equilibrium will shift ihn forward direction
$Q>K$ equilibrium will shift in backward direction
Effect of change in pressure :
If a system in equilibrium consists of gases, then the concentrations of all the components can be altered by changing the pressure. When the pressure on the system is increased, then equilibrium will shift in the direction in which there is decrease in number of moles i.e., towards the direction in which there is decrease in volume.
Effect of change in pressure on melting point : There are two rypes of solids :
Solids whose volume decreases on melting, e.g., ice, diamond, carborundum, magnesium nitride and quartz.
Solid (higher volume) $\iff$ Liquid (higher volume)
The process of melting is facillitated at high pressure, thus melting point is lowered.
Solid whose volume increase on melting, e.g., Fe, Cu, Ag, Au, etc.
Solid (lower volume) $\iff$ Liquid (higher volume)
In this case the process of melring becomes difficult at high pressure, thuse melting point becomes high.
Solubility of substances : When solid substance are dissolved in water, either heat is evolved.
for endothermic solubility process solubility increase with increase in temperature. For exothemic solubility decrease with increase in temperature.
Solubility of gases in liquids : when a gas dissolves in liquid, there is decreases in voolume. Thus increase of pressure will faavour the dissolution of gas in liquid.
Effect of temperature : For endotherimic reacrtion as temperature increases reaction shift in backward direction
$Fe\left(l\right)\iff Fe\left(s\right)$
Above equilibrium is favaured at :

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