How do I solve this AP Chemistry problem?

Question

How do I calculate the activation energy for the reverse of the reaction NO(g) +CO(g) ==>NO(g) CO₂(g), given the activation energy for the forward reaction for the forward reaction is 125kJ/mol and ΔE=-125kJ/mol?

Answer 1

there's a typo in your chemical equation, but that actually won't affect our calculations.  The energy change for a reaction is equal to the difference of the activation energies of that reaction and the reverse reaction.

 

ΔE = act E for - act E rev

-125 = 125 - x

x = 250

 

So the activation energy of the reverse reaction is 250kJ/mol.