Sapling 17

[Yeprem]

Can someone please explain how this works?
A certain reaction has an enthalpy of ΔH=29 kJ and an activation energy of Ea=61 kJ.
What is the activation energy of the reverse reaction?

[ALee_1J]

You really gotta think of this while looking at a reaction profile (energy vs time as the reaction progresses). Ea is the energy barrier so the height of the bump to the energy of the reactants. delta H is the difference in energy between the reactants and products. If you flip the reaction profile/diagram thing, you'll notice that the activation energy of the reverse reaction is equal to the activation of the forward reaction plus the delta H.

[Stephanie Zhang 2K]

It would be helpful to write out a reaction profile! the ∆H enthalpy is the change in energy between the reactants and the products; you take the difference between the initial product energy and the initial reactant energy. The activation energy is the energy barrier that the reaction needs to overcome in order to take place; this is seen as the difference between the "top of the hill" and the reactant initial energy (assuming that the activation energy in the problem is referring to the forward activation energy). Then, to find the activation energy of the reverse process, we add together the activation energy of the forward process and the ∆H for this exothermic process.

[Joshua Eidam 2A]

If you draw out the reaction curve that shows the activation energy and whether it is exothermic or endothermic will be really helpful. Once you determine how the reaction works, you will be able to see how the activation energy, the delta H, and the reverse reaction are related. I believe since the delta H is positive that the reaction is endothermic so you would just subtract the delta H from the activation energy for the forward reaction to get the activation for the reverse reaction.

[Simran Bains 2C]

I thought of it like the diagram that we would draw, where deltaH is the difference in Reactants and Products, and then the activation energy is essentially how high up it goes from the reactants side. So I believe that the reverse activation energy would be just adding up the two.

[derickngo3d]

It is really helpful to look at the reaction enthalpy graph. The activation energy is the height of the mountain, and the change in enthalpy is the difference between the starting and final enthalpy.

[rhettfarmer-3H]

I think the best way to think of this is through the enthaply graph. SO first determine if its Endo or exo. In this case h is postive therefore, it endo. Endo goes to higher energy for products so there is less EA for the reverse. SO we will take the forward and substract it from h.

[abby hyman]

The activation energy of the reverse reaction is the activation energy of the forward, plus delta H