Equilibrium constant (Kc) is related to rate or velocity constants of forward reaction (kf) and reverse reaction (kr) as:
Kc = \(\frac{K_f}{K_r}\)
This equation can be used to determine the composition of the reaction mixture
[Note: The equilibrium refers to the relative amounts of reactants and products and thus a shift in equilibrium in a particular direction will imply the reaction in that direction will be favoured.]