Question

This reaction is endothermic. $$ \mathrm{C}(s)+\mathrm{CO}_{2}(g) \rightleftharpoons 2 \mathrm{CO}(g) $$ Predict the effect (shift right, shift left, or no effect) of these changes. (a) increasing the reaction temperature (b) decreasing the reaction temperature

Short answer

For an endothermic reaction: (a) increasing the temperature shifts the equilibrium to the right, (b) decreasing the temperature shifts the equilibrium to the left.

Step-by-step solution

Understand Endothermic Reactions

Recognize that in an endothermic reaction, heat is absorbed from the surroundings. This means that heat can be considered a reactant. The reaction consumes heat to proceed, and the energy of the products is higher than that of the reactants.

Apply Le Chatelier’s Principle for Temperature Increase

Le Chatelier’s Principle states that if a system at equilibrium is disturbed, the system will adjust itself to counteract the disturbance. Increasing the temperature adds heat to the system, so the equilibrium will shift to consume the excess heat. In an endothermic reaction, this means the equilibrium will shift to the right to form more products.

Apply Le Chatelier’s Principle for Temperature Decrease

Decreasing the temperature removes heat from the system, so the equilibrium will shift to replace the lost heat. For an endothermic reaction, this means the equilibrium will shift to the left, favoring the reactants.

Key concepts

Le Chatelier's Principle

Le Chatelier's Principle is a fundamental concept in chemistry that describes how a chemical system at equilibrium responds to external changes. This principle states that if an external stress—such as changes in concentration, pressure, or temperature—is applied to a system in equilibrium, the system will adjust itself in a way that minimizes the impact of this change.

For example, consider a simple reversible reaction where adding more of a reactant will drive the reaction forward to produce more products, while removing a product will shift the reaction in reverse to produce more of the missing product. This self-adjusting behavior helps the system maintain a state of dynamic balance. Le Chatelier's Principle is primarily used to predict the outcome of changes in a chemical reaction and is crucial for understanding how to control reactions in industrial processes.

Chemical Equilibrium

Chemical equilibrium occurs when a reversible chemical reaction is proceeding in both directions at the same rate, such that the concentrations of the reactants and products remain constant. It's important to note that even though the macroscopic properties do not change, the reaction is still occurring on the molecular level.

Chemical equilibrium is dynamic, meaning that the formation of the products and the reformation of the reactants are happening continuously. Equilibrium does not mean that the reactants and products are present in equal amounts—rather, their ratios will depend on the reaction's specific characteristics, including temperature, pressure, and the inherent properties of the substances involved.

Reaction Temperature Effects

Temperature has a profound effect on the position of chemical equilibrium in a reversible reaction. For endothermic reactions, where heat is absorbed, an increase in the reaction temperature provides additional energy that is necessary for the reaction to proceed, favoring the formation of products. This shift in equilibrium can be understood by picturing heat as a reactant.

On the other hand, a decrease in temperature has the opposite effect. It removes heat from the system, which effectively removes a 'reactant' from the endothermic process, thus shifting the balance toward the reactants. This fundamental understanding of how temperature affects chemical equilibrium is essential not only in academic settings but also in various industrial applications where temperature control is used to optimize product yields.