6.2.6 The Effect of Temperature Changes on Equilibrium (HT only)

Changes in temperature can have a significant impact on the position of equilibrium in a chemical reaction. The effect of temperature changes depends on whether the reaction is endothermicA reaction that ‘absorbs’ heat, where the products have greater energy than the reactants. or exothermicA reaction that releases heat, where the products have less energy than the reactants..

Endothermic Reactions

An endothermic reaction is one that absorbs heat from its surroundings. In an endothermic reaction, increasing the temperature causes the equilibrium to shift in the direction of the products. This means that the relative amount of products at equilibrium increases when the temperature is increased.

Conversely, decreasing the temperature of an endothermic reaction shifts the equilibrium towards the reactants. As a result, the relative amount of products at equilibrium decreases when the temperature is decreased.

Exothermic Reactions

An exothermic reaction releases heat into its surroundings. For exothermic reactions, the effect of temperature changes is opposite to that of endothermic reactions. When the temperature of an exothermic reaction is increased, the equilibrium shifts in favour of the reactants. Consequently, the relative amount of products at equilibrium decreases.

On the other hand, decreasing the temperature of an exothermic reaction causes the equilibrium to shift towards the products. This leads to an increase in the relative amount of products at equilibrium.

Conclusion

By examining the nature of the reaction (endothermic or exothermic) of the reaction, we can predict the effect of temperature changes on the position of equilibrium. An understanding of the heat transfer in chemical reactions and the principles of Le Chatelier's Principle is crucial for making these predictions.