## Endo VS Exo

$K = \frac{k_{forward}}{k_{reverse}}$

205150314
Posts: 106
Joined: Wed Feb 20, 2019 12:16 am

### Endo VS Exo

How are you able to tell whether a a rxn is endo or exo just by the value of the fwd and rev rxns?

Abhi Vempati 2H
Posts: 104
Joined: Fri Aug 09, 2019 12:17 am

### Re: Endo VS Exo

You have to look at the activation energies (not the rate constants). If the fwd reaction has a lower activation energy than the rev reaction, you know that there is a smaller "hump" going forward and a larger one going backward. If you draw the reaction profile, this corresponds to an exothermic reaction.

Similarly, if fwd reaction has a larger activation energy than the rev reaction, you know that there is a larger hump in the fwd direction. This reaction profile (if you draw it) will correspond to an endothermic reaction. Hope this helps!

Myka G 1l
Posts: 100
Joined: Fri Aug 30, 2019 12:17 am

### Re: Endo VS Exo

The activation energy (Ea) for the forward reaction is the potential energy difference between the activated complex and the reactants. For the reverse reaction it is the potential energy difference between the activated complex and the products. If the forward reaction has a lower activation energy than the reverse reaction it is exothermic. The converse applies for endothermic reactions.

Tanmay Singhal 1H
Posts: 143
Joined: Sat Jul 20, 2019 12:16 am

### Re: Endo VS Exo

activation energy for each should tell you

Shutong Hou_1F
Posts: 117
Joined: Sat Sep 14, 2019 12:17 am

### Re: Endo VS Exo

I think that whether a reaction is endothermic or exothermic depends only on the final Gibbs free energy and initial Gibbs free energy. If the reactants have higher free energy, then the reaction is exothermic; if the products have higher free energy, then the reaction is endothermic.