Activation energies for multi-step reactions


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Tyler Angtuaco 1G
Posts: 130
Joined: Wed Sep 11, 2019 12:16 am

Activation energies for multi-step reactions

Postby Tyler Angtuaco 1G » Wed Mar 11, 2020 11:16 am

For a three step reaction, is there a way to determine which of the fast steps has the higher activation energy if we are not provided these values? Question 7.11 only provides us with three sets of reactions (which we have to assume which one is slow and which are fast based on the overall rate law) and the fact that the reaction is exothermic. I was not sure why we can assume the last (fast) step has a higher activation than the first (fast) step.

Jessica Booth 2F
Posts: 101
Joined: Fri Aug 30, 2019 12:18 am

Re: Activation energies for multi-step reactions

Postby Jessica Booth 2F » Wed Mar 11, 2020 12:10 pm

If there is a graph, you can look at the difference between the top of the bump to the starting energy level of the different fast steps to determine which fast step has a higher activation energy. In other words, the fast step with the largest "uphill section" will have the higher activation energy.

BNgo_2L
Posts: 95
Joined: Wed Sep 11, 2019 12:17 am

Re: Activation energies for multi-step reactions

Postby BNgo_2L » Thu Mar 12, 2020 8:10 am

Activation energy is determined by the amount of energy needed for the reactants to go to the transitional state, so on a graph, the activation energy will be the amount of energy from the level of the reactants to the peak (transitional state) of the graph.


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