Suppose that 2.00 moles of HCl in a 1.00L glass flask slowly decomposes into H2 and Cl2. When equilibrim is reached, the concentrations of H2 and Cl2 are both 0.214M. What is the Keq?

Answer 1

Keq = product/ reactant
Write the balanced equation for what you are given. 2HCl--->H2 + Cl2

I believe that's how you start off.

Answer 2

.........2HCl ==> H2 + Cl2
I........2M........0.....0
C........-2x.......x.....x
E.......2-2x.....0.214..0.214

Therefore, at equilibrium, H2 = 0.214, Cl2 = 0.214 and HCl = 2-2*0.214. Substitute into Keq expression and evaluate for Keq.