Answer. A reaction having large value of Kc goes to completion because the equilibrium is established almost on the completion of such a reaction. The reaction mixture consists of almost all the products and reactants are negligible. For example, oxidation of carbon monoxide goes to completion at 1000 K.
2CO (g) + O2(g) <====> 2C02(g) Kc= 2.2 x 1022