Given the reaction at equilibrium: #N_2(g) + O_2(g) + e n ergy rightleftharpoons 2NO(g)# What change will result in a decrease in the amount of #NO(g)# formed?
Decrease the temperature of the reaction to drive the reaction to the left and consume
The forward reaction is an endothermic reaction. This means that the back reaction is exothermic. In the forward reaction, the system absorbs energy from the surroundings and the temperature decreases. Conversely, in the back reaction, the system releases energy to the surroundings and the temperature increases.
So, using Le Châtelier's principle, if you make a change to an equilibrium system, the reaction will shift in the direction that counteracts that change until a new equilibrium is established.
In this case we want the reaction to go backwards to consume
It does this by moving in the back/exothermic direction, which releases heat.