Question

With regard to reaction rate, what is characteristic of a reversible reaction at equilibrium?

Short answer

The reaction rate for a reversible reaction at equilibrium shows equal forward and reverse rates.

Step-by-step solution

Define Reversible Reaction

A reversible reaction is a chemical reaction where the reactants form products, which can in turn react to form the reactants again. This means the reaction can proceed in both the forward and reverse directions.

Define Reaction Rate

The reaction rate is the speed at which a chemical reaction occurs. It is typically expressed as the change in concentration of a reactant or product per unit time.

Understand Equilibrium

A state of equilibrium in a chemical reaction is when the rate of the forward reaction equals the rate of the reverse reaction. This means that there is no net change in the concentrations of reactants and products over time.

Characteristic of Reaction Rate at Equilibrium

At equilibrium, the characteristic of a reversible reaction is that the rate of the forward reaction is equal to the rate of the reverse reaction. This balance in reaction rates ensures that the concentrations of reactants and products remain constant over time.

Key concepts

Reaction Rate

In a reversible reaction, the concept of reaction rate is central to understanding how quickly the reactants are converted to products and vice versa. Reaction rate essentially measures how fast or slow a chemical reaction takes place. For any chemical reaction:

• **Rate of Reaction:** This is typically expressed as the change in concentration of a reactant or product per unit time.
• **Factors Influencing Rate:** Temperature, concentration, surface area, and presence of a catalyst can affect how quickly a reaction reaches completion or equilibrium.
• **Dynamic Behavior:** Even when a reaction appears to have reached completion, some molecules of reactants and products continue to transform back and forth, primarily if the reaction is reversible.

Understanding the reaction rate helps in predicting how long it will take a reaction to reach a state of equilibrium, which is an important aspect of chemical kinetics.

Chemical Equilibrium

Chemical equilibrium is a fascinating state in reversible reactions where two opposing processes happen at the same rate. In essence:

• **Steady State:** At equilibrium, the concentration of reactants and products remains constant because the rate at which the reactants turn into products is perfectly balanced by the rate at which products revert back to reactants.
• **No Visible Change:** Although the reaction appears static, it is dynamic at a microscopic level with continuous interconversion.
• **Equilibrium Constant ( K_{eq} ):** This mathematical expression represents the ratio of the concentrations of products to reactants, explaining the extent to which a reaction proceeds.

Equilibrium does not imply the end of a reaction; rather, it suggests a harmonious balance. This balance is crucial for processes in nature and industries, ensuring reactions are efficient and controlled.

Forward and Reverse Reactions

In reversible reactions, the roles of forward and reverse reactions are central. These directions the reaction can proceed in are defined as:

• **Forward Reaction:** This is when reactants combine to form products. It proceeds from left to right in a chemical equation.
• **Reverse Reaction:** This occurs when the products decompose back into reactants, moving in the opposite direction (from right to left).
• **Interplay at Equilibrium:** At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction. This balance maintains constant concentrations of all species involved in the reaction.

The dynamic equilibrium involving forward and reverse reactions is key to many processes, such as digestion in our bodies and the functioning of natural and synthetic chemical systems.