Exercise 2 | Chemical Kinetics: Mechanisms

The activation energy in the forward direction of an elementary step is 35 kJ.

The activation energy in the reverse direction is 55 kJ.

What is ΔHrxn for this step?

Ea (forward reaction) = Ea (reverse reaction) + ΔHrxn

⇒ ΔHrxn = Ea (forward reaction) - Ea (reverse reaction) = 35 – 55 = -20 kJ