So now what we do is we simply realize that our Q for this system is the concentration of this guy over the concentration of this guy. So let's go back to our nurse equation. Notice that our e for standard conditions cancels out because we have the same type of equation, and so they have the same magnitude of different signs. So when you look the value up on a table you add them up and they cancel out. That's why that e goes away. And now we have E equals negative RTln of Q over N F. Now, F is a constant.