Question

In the reaction, ${N_2} + {O_2}\, \leftrightharpoons 2NO\; + \;heat$ , which of the following conditions is suitable to get a good yield of $NO$ ?
(A) Increase in temperature
(B) Decrease in temperature
(C) Increase in pressure
(D) Addition of Catalyst

Answer 1

The formation of Nitrogen oxide from the reaction of Nitrogen and oxygen is exothermic as a large amount of heat is released after the bond formation. The equilibrium between the reaction is set. We need to shift it in a direction where it will favor product formation i.e. $NO$ .

Complete step by step answer:
Le Chatelier’s principle which is also called the equilibrium law is used to predict the effect of some change in factors on a thermodynamic system that is in chemical equilibrium. The principle was given by French chemist Henry Louis Le Chatelier. He said that equilibrium can adjust the forward and backward reactions in such a way as to negate the changes that are affecting the equilibrium. According to the Le Chatelier Principle, states that a change in temperature, pressure, or concentration of reactants in an equilibrium system will shift the equilibrium to change into a new equilibrium to negate the effect of that change. In the case of changing temperature, adding or removing heat shifts the equilibrium. The given reaction is exothermic, so in case of an exothermic reaction, increasing the temperature will shift the equilibrium in the reverse direction to remove the effect of extra heat but we want a good yield of $NO$ . So, to get that we have to shift the equilibrium in the forward direction, so it will favor product formation more, and to achieve that we have to decrease the temperature so that the equilibrium shifts in the forward direction.
Hence, option (B) is correct.

Note:
Exothermic reactions are those reactions in which heat is evolved from the system to the surrounding after the product formation. In the case of endothermic reactions, the heat is absorbed from the surroundings to the system.