What is the effect of increasing the pressure in a gaseous reaction at equilibrium?

Increasing the pressure in a gaseous reaction at equilibrium affects the position of the equilibrium according to Le Chatelier's principle. This principle states that if a change is applied to a system at equilibrium, the system will adjust itself to counteract that change and re-establish a new equilibrium.

When the pressure is increased, the equilibrium will shift towards the side of the reaction that produces fewer gas molecules. This shift occurs because by favoring the side with fewer molecules, the system can reduce the pressure. Essentially, the system shifts to minimize the effect of the pressure change.

For example, consider a reaction where one mole of gas reacts to produce two moles of gas. Increasing the pressure would cause the equilibrium to shift towards the side that generates only one mole of gas, leading to a reduction in overall gas volume and, consequently, a decrease in pressure.

Thus, the correct answer reflects the behavior of gas reactions under pressure changes, emphasizing the system's response to maintain equilibrium.