Question

What is the effect of increasing the pressure of a reaction mixture at equilibrium if the product side has fewer moles of gas particles than the reactant side?

Short answer

Increasing the pressure will shift the equilibrium towards the products, as they have fewer moles of gas particles.

Step-by-step solution

Understanding the principle of Le Chatelier

According to Le Chatelier's principle, if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change. In this case, we're increasing the pressure of the reaction mixture.

Identifying the effect of pressure on the equilibrium

Increasing the pressure of a system in equilibrium favors the side with fewer moles of gas. This happens because the system can reduce the pressure by shifting towards the side with less volume, which is associated with fewer gas moles.

Predicting the shift in equilibrium

Since the product side has fewer moles of gas particles than the reactant side, increasing the pressure will shift the equilibrium towards the products.

Key concepts

Chemical Equilibrium

Chemical equilibrium represents a state in a chemical reaction where the rates of the forward and reverse reactions are equal, resulting in no overall change in the concentrations of reactants and products over time. It's important to understand that this is a dynamic process, as molecules are constantly reacting and forming products, which subsequently decompose back into reactants. However, when viewed on a macroscopic level, it appears as if the reaction has ceased since there are no visible changes in the system.

Understanding the balance between these forward and reverse reactions is key to manipulating and predicting the behavior of chemical systems. At equilibrium, the ratio of the concentrations of products to the concentrations of reactants, each raised to the power of their stoichiometric coefficients, is constant and is described by the equilibrium constant, K. This concept is crucial as it informs us about the direction and extent to which a reaction will proceed under given conditions.

Equilibrium Shift

An equilibrium shift refers to the change in the position of an established equilibrium in response to an external change, such as variations in temperature, pressure, or concentration of reactants or products. According to Le Chatelier's principle, the system will naturally adjust its equilibrium position to counteract the disturbance and re-establish equilibrium. This principle helps us predict the direction of the shift.

For example, if we increase the concentration of reactants, the system will shift to the right (towards products) to reduce this concentration by forming more products. Conversely, if a product is removed from the system, the equilibrium will shift to the right to produce more of that product. These shifts are essential for chemical industries as they allow the optimization of yields for desired products.

Pressure Effects on Equilibrium

Pressure changes can significantly affect systems in equilibrium when gases are involved. If the reaction experiences an increase in pressure, the system will react by shifting the equilibrium to reduce the pressure. This is achieved by favoring the production of fewer moles of gas, which corresponds to a decrease in volume according to the ideal gas law where Pressure is inversely proportional to Volume.

In the context of the provided exercise, increasing pressure will prompt the equilibrium to shift towards the product side, as it has fewer moles of gas, and thus occupies less volume. This behavior allows chemical engineers to manipulate conditions to favor the production of a certain product in reactions involving gases. Understanding the subtleties of pressure effects on equilibrium is a fundamental aspect of chemical reaction engineering and process control.