 So we'll simply go back to chemical reaction kinetics. We have a state A and a state B We know that there is a reaction K A to B and there is another reaction K B to A We also know that the chemical equilibrium constant uppercase K The ratio of B to A That's going to be again at the equilibrium the number of molecules going from A to B divided by the rate going from B to A And another way of writing that is going to be at the equilibrium. That's going to be the number of molecules in state B divided by the number of molecules in state A the What I want to know now is that how does something let's focus on state A for instance How does the number of molecules in state A the derivative change as a function of time? well There's going to be the flux away from state A That's the number of molecules per second multiplied by the density leaves some space there So that's going to be proportional to the number of molecules A at that time and then things are moving away So it's a minus sign and that's K from A to B, right? But I'm also gaining molecules I'm gaining the molecules going from B to A multiplied by the current concentration in state B There are a few too many variables here so We can introduce that n zero is always equal n A plus n B That's particularly going to be true at infinity, but n zero does not change And that means that I can write this n B as n zero minus n A and That means that this becomes K A to B leaves some space Nat plus K B to A and Zero minus n A Multiplied by K B to there is already a minus sign there. So I can say K B there B to A there Already here in principle we have the results The derivative here is now going to be the change here is going to be proportional to the current concentration in state A But you see here there we have the sum of the two reaction rates Which initially looks really strange, but it's not that stupid if we're thinking about the range at which I approach equilibrium Things moving from the left to right and right to left. They're both going to help me equilibrate, right? So that the total apparent rate with which I appeared to the reaction appears to happen It's actually the sum of both rates very surprising We can do this slightly more formally and solve the entire partial differential equation But it's not really that important so I'm not going to do it the book does it if you want to follow it But the idea is that we have an apparent rate K up Which is equal K from A to B plus K B to A In practice, this is much easier to measure in the lab because I don't have to worry about molecules going in the wrong direction This is just everything just measure how fast the reaction happens. I don't care in which direction it happens We're going to need a different plot to plot that in it's called the Chevron plot and let me show you what it looks like