Why are stoichiometric coefficients the exponents in the equilibrium constant expression?

[Thumbz]

Ok, I've always wondered, is there any explanation behind the Law of Mass Action? In my textbook, the law is just described as being an example of the empirical nature of chemistry, and no reason for why that describes the equilibrium condition is given. Is there an intuitive reason why the stoichiometric coefficients would be the exponents to the coefficients in the equilibrium equation? If there is, I fail to see it.

 

[Borek]

Reasons become more or less obvious when you treat the system using thermodynamics. For simple systems it can be also explained using kinetic approach to equilibrium. But there is probably no simple explanation that can be used by someone just starting to learn chemistry.