Temperature affects equilibrium because it changes the rates of the forward and reverse reactions differently, depending on whether the reaction is exothermic or endothermic. This is explained by Le Chatelier’s Principle.
Key points:
- Exothermic reaction (releases heat):
- Increasing temperature adds heat, so the system shifts toward reactants (reverse reaction) to absorb the extra heat.
- Decreasing temperature favors products (forward reaction).
- Endothermic reaction (absorbs heat):
- Increasing temperature favors products (forward reaction) to use the extra heat.
- Decreasing temperature favors reactants (reverse reaction).
- Effect on equilibrium constant (K):
- K changes with temperature.
- For exothermic reactions: higher T → lower K
- For endothermic reactions: higher T → higher K
Summary: Temperature can shift the equilibrium position and also change the value of K, unlike concentration or pressure changes, which only shift the position.