Question

List four factors that can shift the position of an equilibrium. Which one can alter the value of the equilibrium constant?

Short answer

The four factors that shift the position of an equilibrium are changes in concentration, temperature, pressure, and the introduction of a catalyst. Only changes in temperature can alter the equilibrium constant.

Step-by-step solution

- Factors that Shift Equilibrium

The four main factors that can shift the position of an equilibrium are: 1. Change in Concentration: Adding more reactants pushes the equilibrium point towards the products side while adding more products pushes the equilibrium towards the reactants. 2. Change in Temperature: Changing the temperature will favor either the exothermic or the endothermic reaction, shifting the equilibrium. 3. Change in Pressure: Increasing the pressure will shift the equilibrium towards the side with fewer gas particles, while reducing the pressure shifts it towards the side with more gas particles. 4. Introduction of a Catalyst: A catalyst speeds up both the forward and reverse reactions and can quickly establish equilibrium, but does not shift its position.

- Factor that Alters the Equilibrium Constant

Only changes in temperature can alter the value of the equilibrium constant. This is because the equilibrium constant (K) is directly related to the standard Gibbs free energy change, which is temperature-dependent. Changes in concentration or pressure cause the system to shift to regain equilibrium but do not affect the equilibrium constant. Catalysts also do not affect the equilibrium constant, as they speed up both the forward and reverse reactions equally.

Key concepts

Factors That Shift Equilibrium

Understanding what factors can shift chemical equilibrium is crucial to comprehend the dynamic nature of reactions. When a system at equilibrium experiences a change, the balance between the reactants and products is affected, and the system shifts in an attempt to reestablish equilibrium. The four main factors identified include changes in concentration, temperature, pressure, and the introduction of a catalyst.

Concentration

Altering the concentration of reactants or products shifts the equilibrium to counterbalance the change. If additional reactants are introduced, the system will shift toward the products to use up the added reactants. Conversely, adding more products causes the system to favor the reactants to reduce the product concentration.

Temperature

Temperature changes affect exothermic and endothermic reactions differently. An increase in temperature typically favors the endothermic direction, while lowering the temperature favors the exothermic reaction, thus shifting the equilibrium accordingly.

Pressure

In reactions involving gases, changing the pressure has an impact on equilibrium. Increasing pressure shifts the balance toward the side with fewer moles of gas, and decreasing pressure favors the side with more moles of gas.

Catalysts

While catalysts speed up the rate at which equilibrium is reached by enhancing both the forward and reverse reactions, they do not shift the position of the equilibrium itself.

Equilibrium Constant

The equilibrium constant, represented as K, is a quantitative measure that reflects the ratio of the concentration of products to the concentration of reactants at equilibrium, raised to the power of their respective coefficients in the balanced equation. The value of K offers insight into the position of equilibrium and indicates the favorability of the forward or reverse reaction.

It is crucial to recognize that the equilibrium constant is only altered by changes in temperature. This is because K is related to the standard Gibbs free energy change, a thermodynamic function that varies with temperature. When temperature increases or decreases, the balance between the quantity of products and reactants at equilibrium changes, which is directly reflected in the value of K. Conversely, adjustments in concentration, pressure, or the introduction of a catalyst achieve equilibrium shifts without affecting the constant's value.

Le Chatelier's Principle

Le Chatelier's Principle provides a qualitative view by predicting how a change in conditions can affect the position of an equilibrium. It states that when a system at equilibrium faces an external stress such as changes in concentration, temperature, or pressure the system will adjust itself in a manner that tends to counteract or reduce the effect of the disturbance.

For example, an increase in reactant concentration would result in the system producing more products. Upon experiencing a rise in temperature for an exothermic reaction, the system would shift toward the reactants to absorb the excess heat. Similarly, an increase in pressure would shift the equilibrium to the side of the reaction with fewer gaseous molecules. Le Chatelier's Principle is an essential concept for predicting the outcome of system perturbations and is widely applied in various industrial processes to improve yields.