Question

How does the equilibrium constant change with temperature?

Answer 1

For an exothermic reaction (`ΔH` is negative), `K` decreases with an increase in temperature.

For an endothermic reaction (`ΔH` is positive), `K` increases with an increase temperature.

You can calculate the effect of changing temperature on the equilibrium constant by using the van't Hoff equation

`(dlnK)/(dT) = (ΔH^°)/(RT^2)`, where `R` is the Ideal Gas Constant.

If you integrate this equation from `T_1` to `T_2`, you get

`ln((K_2)/(K_1)) = (ΔH^°)/R (1/(T_1) – 1/(T_2))`

Thus, if you know the `ΔH^°` and the equilibrium constant at one temperature, you can calculate the equilibrium constant at some other temperature.