At chemical equilibrium state, when pressure, temperature or number of moles of components change, then the net results of reaction change, this is called as Le Châtelier principle.
Temperature:
Ammonia is formed by reaction of hydrogen and nitrogen and the reaction is reversible.
N2 + 3H2 ↔ 2NH3
Here forward reaction evolved heat and is called as exothermic reaction, whereas reverse reaction absorbs heat and is called as endothermic reaction. It the temperature of equilibrium mixture of hydrogen, nitrogen and ammonia is increased, then the reaction which absorbs heat will be favored and ammonia is decomposed.
Pressure:
N2 + 3H2 ↔ 2NH3
When ammonia is formed, the volume of reactants decreased, hence increased in pressure will favor the formation of ammonia
Concentration of reagents:
2NO + O2 ↔ 2NO2
When more number of NO or O2 is added, the equilibrium shifts to the right producing more number of NO2
When more no of NO2 is added, the equilibrium shifts to the left producing more number of NO and O2.