The van’t Hoff equation is a formula that shows how the equilibrium constant (K) of a chemical reaction changes with temperature. It connects thermodynamics (enthalpy, Gibbs free energy) to how reactions behave under different temperatures.
Here’s a explanation:
1. What the van’t Hoff equation says
- If a reaction is exothermic (releases heat), increasing temperature decreases K → equilibrium shifts toward reactants.
- If a reaction is endothermic (absorbs heat), increasing temperature increases K → equilibrium shifts toward products.
In short: Temperature changes affect equilibrium, and the van’t Hoff equation quantifies this.
2. Relation to Gibbs free energy
- Gibbs free energy (ΔG) and the equilibrium constant (K) are connected:
- ΔG° tells whether a reaction is spontaneous.
- K tells how far the reaction goes at equilibrium.
- By combining ΔG° = −RT ln K with the van’t Hoff equation:
- We can see how temperature changes affect ΔG° and K, and thus the position of equilibrium.
3. Why it matters
- In industrial chemistry, the van’t Hoff equation helps engineers choose the best temperature to maximize product yield.
- Example: Haber process for ammonia
- Exothermic reaction → high temperatures reduce K, so a balance is needed between reaction rate and yield.
Summary
- Van’t Hoff equation → shows how equilibrium changes with temperature.
- Gibbs free energy → predicts spontaneity and relates to K.
- Together → they help predict how reactions behave and how to optimize conditions.