Chemical Change: Factors Affecting Equilibrium

Understanding Equilibrium

Chemical equilibrium is the state in a chemical reaction when the concentrations of the products and the reactants are unchanged over time.
It is reached when the rate of the forward reaction equals the rate of the backward reaction.
Reactions that can achieve an equilibrium are termed reversible reactions, denoted by the symbol ⇌ in chemical equations.

Conditions Affecting Equilibrium

Three key factors can shift the position of equilibrium: concentration, temperature, and pressure.
Le Chatelier’s Principle can be used to predict how changes in conditions affect the position of equilibrium.

Concentration

Increasing the concentration of reactants shifts the equilibrium towards the products. There is more chance for the reactants to collide and react, thus increasing the forward reaction.
Increasing the concentration of products shifts the equilibrium towards the reactants. This can reduce the product concentration until a new equilibrium is established.

Temperature

Increasing the temperature favours the endothermic reaction (one that absorbs heat). Thus, if the forward reaction is endothermic, raising the temperature shifts equilibrium towards the products. If the backward reaction is endothermic, equilibrium shifts towards the reactants.
Decreasing the temperature favours the exothermic reaction (one that releases heat). Hence, if the forward reaction is exothermic, lowering the temperature shifts equilibrium towards the products.

Pressure

This only affects gaseous reactions. Increasing pressure shifts the equilibrium towards the side with fewer gas molecules, reducing the pressure.
Decreasing pressure shifts equilibrium towards the side with more gas molecules, increasing the pressure.

Catalysts and Equilibrium

A catalyst speeds up the rate of both the forward and backward reactions, helping achieve equilibrium faster.
Although a catalyst accelerates a reaction, it does not change the position of equilibrium.

Remember that understanding these concepts involves relating them to practical examples, and being familiar with the use of these principles in context.