In: Chemistry
The equilibrium constant Kc for the following reaction is 4.59 × 10-7 at 730oC. 2HBr(g) ⇌ H2(g) + Br2(g) Suppose 3.20 mol HBr and 1.50 mol H2 are added to a rigid 12.0-L flask at 730oC. What is the equilibrium concentration (in M) of Br2?
[HBr] = moles/L = 3.20 mol/12.0 L = 0.267 M
[H2] = 1.50 mol/12.0 L = 0.125 M
2HBr <====> H2 + Br2
initial (M) 0.267 0.125 0
change(M) -2x +x +x
equilibrium(M) (0.267-2x) (0.125 +x) x
-----------------------------------------------------------------------
Kc = [H2][Br2]/[HBr]^2
4.59 x 10^-7 = (x)(0.125 + x)/(0.267 - 2x)^2
4.59 x 10^-7 = 0.125x + x^2/(0.0713 - 1.068x + 4x^2)
1.84 x 10^-6x^2 - 4.902 x 10^-7x + 3.27 x 10^-8 = 0.125x + x^2
x^2 + 0.125x + 4.902 x 10^-7 = 0
x = 0.125 M
So the concentration of [Br2] = 0.125 M