Question

An endothermic reaction was found to have an activation energy of 100 kJ. If this reaction is reversed, the activation energy is only 20 kJ. What is the value of delta H for the endothermic reaction?

Answer 1

For an endothermic reaction, Ea forward = Ea reverse + delta E rxn.

Answer 2

So the answer would be positive 120 kJ?

Answer 3

No. If Ea forward is 100 and Ea reverse is 20, then delta E reaction is 80.

Answer 4

I looked for and count not find a good diagram. Finally I succeeded.
http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm
You can see that 40 + 30 = total = 70 for exothermic and equally you see that 100 = total = 20 + 80
http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm