Hello everyone, Here's my question. We have a reaction with an overal enthalpy change of -66KJ. The activation energy is 7KJ. We want the Ea for the reverse reaction. Formula: Ea (rev) = ∆E + Ea (fwd) So I wrote: Ea (rev) = -66 + 7 = 59 KJ. But the corrected exercise says: 66+7 = 73KJ. Why did we add 66, if it's a negative value? Thank you, J.