2 SO2(g) ⇌ O2(g) + 2 SO3(g) + heat
What will happen if the temperature is decreased?
Le Chatelier's Principle says, in most unsophisticated language, that a system in equilibrium will try to undo what we do to it. So if we take the heat away, the system will try to replace the heat. How can it do that? Obviously, if the reaction produces heat it will replace it by shifting to the right. That will reduce SO2 and produce more O2 and SO3 and heat.
If the temperature of the system is decreased, according to Le Chatelier's principle, the system will try to counteract the change by shifting the equilibrium in the direction that will produce more heat.
In this reaction, heat is treated as a reactant, which means that decreasing the temperature will shift the equilibrium to the left, favoring the reactants. As a result, the concentrations of SO2 and O2 will increase, while the concentration of SO3 will decrease.
If the temperature of the system described by the equation 2 SO2(g) ⇌ O2(g) + 2 SO3(g) is decreased, the equilibrium will shift to the left. This means that the reaction will favor the formation of SO2 and O2 rather than SO3.
To understand why this occurs, we need to apply Le Chatelier's principle, which states that if a stress is applied to a system at equilibrium, the system will respond by shifting in the direction that minimizes the effect of the stress.
In this case, decreasing the temperature is a stress on the system. According to the reaction equation, the forward reaction (from left to right) is exothermic because it releases heat. By decreasing the temperature, we are effectively removing heat from the system.
To counteract this decrease in temperature, the system will shift in the endothermic direction, which is towards the left. This means that the equilibrium will favor the formation of more SO2 and O2 and less SO3.
In summary, if the temperature is decreased, the equilibrium of the system described by the given reaction will shift to the left, favoring the production of SO2 and O2.