When the volume of the container with the equilibrium system PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) is reduced, the system will shift to the left (reactants) to produce fewer moles of gas according to Le Chatelier's principle. The correct answer is option C.
Le Chatelier's principle states that if a dynamic equilibrium is disturbed by changing conditions, the position of the equilibrium moves to counteract the change. In the chemical equation PCl₅(g) ⇌ PCl₃(g) + Cl₂(g), we have 1 mole of gas on the reactants side and 2 moles of gas on the products side. When the volume of the container is halved from 2.0 L to 1.0 L, the pressure in the container increases, which favors the side of the reaction that produces fewer moles of gas. Therefore, the system will shift to the left (reactants) and the correct answer is C. The reactions shift to the left (reactants) to produce fewer moles of gas.
The initial interpretation stating that the reaction would shift to the right is incorrect because it does not account for the fact that there are more moles of the product than a reactant, which contradicts the direct relationship between volume and pressure in a gas system. The incorrect interpretation suggests an equal number of moles on both sides, which is not the case for this reaction.
Furthermore, the application of stoichiometry and gas laws indicates that the equilibrium will shift to the side with a smaller total volume of gas when pressure is increased due to a reduction in container volume.
Therefore, option C is correct.