#K_(ep)# is the equilibrium product constant. It determines what you have more of, or what is "favored". If #K_(eq)# is less than one, you have more reactants. If it is greater than 1 you have more products.
#K_(eq)# is calculated by taking the concentration of the products divided by the concentration of the reactants.
For the balanced reaction:
#aA + bB -> cC + dD#
the equilibrium constant, #K_(eq )#is:
#K_(eq) = ([C]^c*[D]^d)/([A]^a*[B]^b)#
the above example is from: http://www.chemicool.com/
Note that the coefficients become exponents.
Also know that concentrations are never added or subtracted, only multiplied and divided.
The unit for concentration is usually moles/liter (Molarity)
