Why Doesn't Changing Reactant Concentration Affect the Equilibrium Constant?

[johndoe3344]

Homework Statement

Not really a textbook question, but I've read from numerous sources that changing the concentration of the reactants/products won't change the equilibrium constant. Why isn't this contradictory?

Assume the reaction:
xX + yY <---> zZ
where x,y,z are the coefficients of X,Y,Z


Keq = [Z]^z/[X]^x[Y]^y

So if I change the concentration of say, X, then won't Keq change by definition?

 

[chemisttree]

No. The constant will remain constant. The concentration of Z and/or Y will change accordingly to maintain the equality.

 

[johndoe3344]

Thanks a lot. That cleared it up for me.