Question

What is the equilibrium pressure of H2 (g) produced by the reaction: H2 (g) 2 H (g) starting with 6.5 x 10^-5 bar of H (g), under conditions where Kp = 7 x 10^-21?

Answer 1

................H2(g) ==> 2H(g)

I................0................6.5E-5 bar
C.............+x................-2x
E...............x...............6.5E-5 - 2x
Kp = p^2H/pH2
Kp = (6.5E-5-x)^2/x = 7E-21 where x = pressure
Substitute the E line into Kp expression.
Solve for x = pressure in units of bar