For example consider:
$$aA + bB \rightarrow pP + nN$$ where $a, b, p$ and $n$ are moles.
The equilibrium constant is $$ \frac{[P]^p [N]^n }{[A]^a [B]^b}$$ Where does this come from? I don't understand why anyone would multiply the concentrations of the products together and then divide it by the product of the reactants together. There doesn't seem to be anything in my prior experience to justify that. And why are the exponents the number of moles? What is the physical meaning of an equilibrium constant?
