Final answer:
Decreasing the pressure by increasing the volume causes the reaction to shift towards the side with the most moles of gas according to Le Chatelier's principle, in order to accommodate the change and re-establish equilibrium.
Step-by-step explanation:
When you decrease the pressure in a reaction by increasing the volume, the reaction initially experiences a decrease in gas molecule concentration. In response to this change, according to Le Chatelier's principle, the reaction will shift or adjust to minimize the stress introduced by the change in conditions. If there are different numbers of moles of gases on either side of the equilibrium, the equilibrium will shift toward the side with the most moles of gas. In a provided example where there are three moles on the reactant side and two moles on the product side, the equilibrium shift will be towards the reactants (to the left) when the pressure is decreased. This is because the side with more moles of gas (the reactants with three moles) will better "accommodate" the increase in volume, or decrease in pressure.