The equilibrium constant, Kc, for the following reaction is 4.76104 at 431K. PCl5(g)PCl3(g)+Cl2(g) When a sufficiently large sample of PCl5(g) is introduced into an evacuated vessel at 431K, the equilibrium concentration of Cl2(g) is found to be 0.317 M. Calculate the concentration of PCl5 in the equilibrium mixture. [PCl5]= M