Concept:Le Chatelier’s principle explains how the equilibrium shifts when pressure or temperature is changed.
Explanation:The reaction is
2SO2(g)+O2(g)⇌2SO3(g).
There are 3 gas molecules on the reactant side and 2 gas molecules on the product side.
When pressure is decreased, the equilibrium shifts toward the side with more gas molecules, which is the reactant side.
This shift increases the equilibrium concentrations of
SO2 and
O2.
A catalyst only speeds up the reaction, but it does not change the equilibrium position.
The forward reaction is exothermic, so increasing temperature favours the reverse reaction, not the forward reaction.
Answer:C. Decrease in pressure increases the equilibrium concentration of
O2.