## Pre-Equilibrium

Charisse Vu 1H
Posts: 101
Joined: Thu Jul 25, 2019 12:17 am

### Pre-Equilibrium

Why do we use the pre-equilbrium approach instead of the other methods presented in class?

Ryan Narisma 4G
Posts: 104
Joined: Fri Aug 30, 2019 12:18 am

### Re: Pre-Equilibrium

Hi Charisse Vu 1H! We use the pre-equilibrium approach because it makes it easier to relate the rates of the forward and reverse reaction in the elementary reaction that occurs before the slowest step. The steady state approximation involves the use of differential equations which make it harder for us to create a rate law. The pre-equilibrium approach allows us to set the rates of the forward and reverse reaction as equal seeing as the elementary step is in equilibrium. With the rates equal we can solve for the intermediate concentration and substitute in the rate law of the slowest elementary step. I hope this helps!

Sam McNeill 1E
Posts: 110
Joined: Sat Aug 24, 2019 12:17 am

### Re: Pre-Equilibrium

Lavelle also specified that we will only be using the pre-equilibrium approximation and not the steady state.

RRahimtoola1I
Posts: 102
Joined: Fri Aug 09, 2019 12:15 am

### Re: Pre-Equilibrium

You use the pre-equilibrium method when the earlier step is the fast step and the later step is a slow step. You can then think of the fast step as being almost at equilibrium and use that to solve.