What happens to the number of moles in a reaction upon increasing pressure?

When pressure is increased in a chemical reaction that involves gaseous reactants and products, the equilibrium position will shift toward the side of the reaction that has fewer moles of gas. This is based on Le Chatelier's principle, which states that if a system at equilibrium is subjected to a change in conditions, the system will adjust to counteract that change and restore a new equilibrium.

In systems with gases, increasing pressure essentially compresses the gas molecules, and the system will respond by favoring the direction that produces the fewest gas molecules to relieve the pressure. Therefore, if one side of the equation has fewer moles of gas compared to the other side, the equilibrium will shift in that direction to decrease the overall pressure.

This principle is particularly relevant in reactions where the number of moles of gas on the reactant side is different from that on the product side. This is why the answer indicating a shift toward the side with fewer moles of gas is the correct interpretation of the impact of increased pressure on equilibrium position.