Rate Determining

[Pooja Nair 1C]

How do you determine whether a step in a mechanism is slow or fast if they don't already give it to you?

[Karen Ung 2H]

According to my TA, information on whether the steps in a mechanism are slow or fast will be given.

[704887365]

If they give you graphs with activation energy, the graph with the higher activation energy will be slower than the other bc it will take longer and more energy to carry out the reaction.

[Michael Downs 1L]

If the slow step is listed first, then you don't have to worry about calculating any other steps listed below it

[Jennifer Ho 1K]

The slow step should be given, and the other steps are assumed to be fast.

[GabrielGarciaDiscussion1i]

One way to help determine is the the number of molecules needed to combine. So more often than not, a bimolecular reaction will be slower than a unimolecular. Then termolecular being slower than bimolecular. THIS IS NOT FOOL PROOF OR ANY KIND OF LAW TO USE 100% OF THE TIME, just something to consider. Also, look at the Activation energies.

[Clarissa Molina 1D]

Do you always ignore the reverse of the slow step? Why?

[GabrielGarciaDiscussion1i]

Do you always ignore the reverse of the slow step? Why?

Well the idea is that when it comes to the slow step, the reaction produces products slowly in comparison to the other reactions so that the slow reaction can only proceed forward for a significant amount of time since there is not a significant enough amount of product to proceed with the reverse rxn. It reaches equilibrium so slowly that we can negate the reverse k for the slow reaction.