the equilibrium constant is the ration of product concentration to reactant concentration at equilibrium. a reaction will likely go to completion if the equilibrium constant is what?
k <1 reactants favored.
k = 1 equilibrium
k >1 products favored.
Here is a good site to read more about it.
http://www.800mainstreet.com/7/0007-007-Equi_exp_k.html