Reverse Activation Energies

Arrhenius Equation:

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Josiah Chung 1G
Posts: 16
Joined: Fri Sep 25, 2015 3:00 am

Reverse Activation Energies

Postby Josiah Chung 1G » Sun Mar 06, 2016 9:20 pm

On one of the past final exam questions it says that for an exothermic reaction the reverse activation energy equals delta(H) + Ea. I wasn't able to find any information on this in the course reader; what are the rules for the reverse activation energy for an endothermic reaction

Annie Qing 2F
Posts: 28
Joined: Fri Sep 25, 2015 3:00 am

Re: Reverse Activation Energies

Postby Annie Qing 2F » Mon Mar 07, 2016 3:29 pm

So reverse activation energies are just imagining the reverse reaction occurring. It's easier to visualize it when you think about the graphs of exothermic and endothermic reactions.

Exothermic Reaction
exothermic.png (25.19 KiB) Viewed 788 times

It makes sense that the reverse activation energy for an exothermic reaction would be ∆H + Ea since those values added together gives you the height of the hump if you imagine the graph mirrored or going backwards.

Endothermic Reaction
endothermic.png (12.65 KiB) Viewed 788 times

For an endothermic reaction, the reverse activation energy could be given by Ea - ∆H.

Hope this helps!

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