Question

At a certain temperature, the reaction has Kc = 5 x 108. If a reaction mixture at equilibrium contains 0.26 M of H2 and 0.087 M of Cl2, what is the concentration of HCl?

Answer 1

.....H2 + Cl2 ==> 2HCl
E...0.26..0.087....x

Kc = (HCl)^2/(H2)(Cl2)
You know Kc, (H2), and (Cl2), substitute and solve for HCl.