Hey, everyone. So in this example question, it says a certain reaction has an enthalpy value of -20 kilojoules and an activation energy of 40 kilojoules. A catalyst is found that lowers the activation energy of the reaction by 10 kilojoules. What is the total difference in energy between the products and the transition state?

All right, so they're telling us here our enthalpy value. So this is ΔH and we can say here ΔE also can fill in and it's -20. So let's say that we're our reactants start here at 40 kilojoules, and -20 means our products are 20 kilojoules lower, so they're here at 20 kilojoules. Activation energy. Remember, activation energy is the difference in height between my transition state and my reactant line. So that would mean my transition state which is up here would have to be 80. The difference between these two is what my activation energy is.

Now remember ΔH, Oregon ΔE equals products minus reactants. So it D be 20, -, 40, which is how we got that -20, all right. So now they're saying that we used a catalyst which lowers the energy of activation. So here we were at 80 for the transition state, it gets lowered by 10. So now we're at 70. We're still at 40 for the reactants. That doesn't change and my products are still down here at line 20.

So now we have to calculate the difference. This ΔH or ΔE doesn't change. It's still going to be -20 and then here differences in energy between products and the transition state ear if we're looking at what's the total difference in energy between products and transition state. So we're looking at this total distance here, right. So here we'd say total difference in energy between products and the transition state, products are at 20, transition state is 70. So that would be a difference of 50 kilojoules total.

OK. So that's the total difference. We start out with a total difference of 60 kilojoules between products and transition state. We add the catalyst, the overall energy is lowered by that much. It'd be 50 here. If we wanted to look at the new activation energy, we could also do that. The activation energy here, the new one, would be 70 minus the 40, so it would be 30 kilojoules. And again ΔH or ΔE would still be -20 kilojoules. So this is all the information we could tell for this particular energy diagram once we've introduced the catalyst.