If the pressure of a system is increased, in which direction will the equilibrium shift?

When the pressure of a system at equilibrium is increased, the equilibrium will shift in the direction that results in fewer moles of gas. This principle is based on Le Chatelier's principle, which states that if a change is applied to a system at equilibrium, the system will adjust to counteract that change.

In a chemical reaction involving gases, the total number of moles of gas on each side of the reaction can differ. When the pressure is increased, the system responds by shifting towards the side with fewer moles of gas in order to reduce the pressure. This is because a decrease in the number of gas particles will result in a corresponding decrease in the overall pressure exerted by the gas molecules.

For example, if a reaction has four moles of gas on the reactants side and two moles on the products side, increasing the pressure will drive the reaction toward the products side, where there are fewer moles of gas. This shift helps to partially alleviate the increase in pressure by decreasing the number of gas molecules present in the system. Thus, the correct response to the situation described is that the equilibrium shifts to where there are fewer moles.