With the help of Le-Chatelier’s principle, determine the favourable conditions of concentration, temperature and pressure for the reaction

(i) Effect of concentration. Increase in concentration of reactants (N₂, H₂) will shift the equilibrium in the forward direction to form more ammonia in order to decrease their concentrations. The addition of extra NH₃ from outside to the equilibrium mixture will shift the equilibrium in the backward direction. Thus, the addition of N₂ and H₂ favours the formation of ammonia.
(ii) Effect of temperature. The forward reaction is exothermic in nature while the backward reaction is endothermic in nature. According to Le-Chatelier’s principle, on decreasing the temperature, the equilibrium shifts towards that direction where the evolution of heat takes place in order to nullify the effect of decreasing temperature. Thus, a decrease in temperature favours the formation of ammonia.
On the other hand, on increasing the temperature the equilibrium shifts towards the backward direction where absorption of heat takes place in order to nullify the effect of the rise in temperature. Thus, lower temperature favours the formation of ammonia.
(iii) Effect of pressure. On increasing the pressure, the number of moles per unit volume increases and thus according to Le-Chatelier’s principle, the equilibrium shifts towards that side where the number of moles per unit volume decreases in order to nullify the effect of an increase in pressure. On the other hand, on decreasing the pressure, the equilibrium shifts towards the backwards direction i.e. ammonia decomposes to give N₂ and H₂. Thus, an increase in pressure favours the formation of ammonia.
Hence favourable conditions in the formation of ammonia are:
(i) The addition of N₂ and H₂ 
(ii) Lower temperature
(iii) Higher pressure.