2NO(g) + O₂(g) ⇋ 2NO₂(g) + heat

In this reaction how do the following changes influence the amount of the product?

a) Decrease in temperature

b) Increase in pressure

c) Increase in the concentration of oxygen

a) In the above reaction, on decreasing the temperature the system tries to increase the temperature by evolving heat. So the rate of exothermic reaction will increase. So, the above reaction will proceed in the forward reaction for increasing the temperature. Hence the formation of NO₂ will increase.

Note- Exothermic reactions are those reactions which evolve heat.

b) In the gaseous system, a decrease in the number of molecules helps to decrease the pressure. According to Le Chatelier principle, If we increase the pressure then the number of molecules per unit volume increases which results in increment in the number of effective collisions. So, to decrease the pressure, the reaction will decrease reactant molecules and the reaction will proceed in that direction to attain equilibrium where the number of molecules is less. So the above reaction will proceed in forwarding direction. So in the above reaction, the reactant molecules will react and form product very easily because there are fewer molecules at product side. Hence the formation of NO₂ will increase.

c) On increase in the concentration of oxygen, the reaction will proceed in a forward direction to attain equilibrium by decreasing concentration of reactants. So, the amount of NO₂ will increase.