Chemistry in Society: Equilibria

Chemical Equilibria in Society

Understanding Equilibria Behavior

The concept of dynamic equilibrium is fundamental in understanding how reactions behave.
A dynamic equilibrium is achieved in a closed system when the rate of the forward reaction equals the rate of the reverse reaction.
This doesn’t mean that the reactions stop but that the concentrations of reactants and products do not change over time.
An equilibrium can be approached from either direction.

The Role of Le Chatelier’s Principle

Le Chatelier’s Principle is a tool that predicts how equilibrium systems respond to external changes.
The principle states that a change in any condition of a balanced system will cause the system to adjust so that the change is counteracted.
External changes can include alterations to pressure, temperature or concentration of reactants and products.
The principle provides a qualitative, rather than quantitative, understanding of equilibrium shifts.

Impact of Concentration Changes

For reactions in equilibrium, increasing the concentration of reactants will shift the equilibrium to the right, generating more product. Conversely, decreasing the concentration of reactants shifts the equilibrium to the left.
Conversely, increasing the concentration of products will shift the equilibrium to the left, generating more reactants, while reducing the concentration of products shifts the equilibrium to the right.

Influence of Pressure and Volume Changes

In gas-phase reactions, changes in pressure or volume can alter the position of equilibrium. Increasing pressure will favor the side of the reaction with fewer gas molecules, and vice versa.
If the reaction produces the same number of gas molecules on both sides, changes in pressure or volume will not affect the equilibrium.

Effect of Temperature Changes

For exothermic reactions, an increase in temperature shifts the equilibrium to the left (favoring reactants), since the reaction can be thought of as “removing” heat. For these reactions, decreasing the temperature shifts the equilibrium to the right (favoring products).
For endothermic reactions, increasing the temperature shifts the equilibrium to the right (favoring products), since the reaction can be thought of as “absorbing” heat. Decreasing the temperature for these reactions shifts the equilibrium to the left (favoring reactants).

The Role of Catalysts in Equilibrium

A catalyst increases the rate at which equilibrium is achieved but does not change the equilibrium position. It achieves this by providing an alternative reaction pathway with a lower activation energy.

Remember, understanding the responses of systems to external forces is key to manipulating chemical reactions for societal benefit. Every reaction is a balance of various factors and requires careful control to optimise outcomes.