At 1280C the equilibrium constant Ke for the reaction Br2g 2

At 1280°C the equilibrium constant Ke for the reaction Br2(g) 2Br(g) is 1.1 x 10-3. If the initial concentrations are [Br21-0.0390 M and [Brl-o0390 M, calculate the concentrations of these two species at equilibrium. [Brleq =

Solution

                      Br2(g) -----------> 2Br(g)

I                   0.039                  0.039

C                +x                        -2x

E               0.039+x               0.039-2x

         Kc   = [Br]^2/[Br2]

       1.1*10^-3 = (0.039-2x)^2/(0.039+x)

      1.1*10^-3 *(0.039+x)   = (0.039-2x)^2

       x = 0.0156

[Br2]    = 0.039+0.0156    = 0.0546M

[Br]      = 0.039-2*0.0156   = 0.0078M