So first let's examine that situation at hand. Notice our first step is now the fast step and that means 1 mol of N o will react with 1 mol of BR two to produce 1 mol of no BR two. And this step will be really quick meaning that by the time it gets here it's going to go back. And in fact we're going to assume that this step, this reaction first reaction is at equilibrium before this reaction even begins. And we're going to assume that the concentration of this guy is very, very small. Now let's look at the second step.