How does the equilibrium constant change with temperature?

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Answer 1 · 2014-01-11T21:46:03

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.