Question

A mixture initially contains A, B, and C in the following concentrations: [A] = 0.450 M , [B] = 1.10 M , and [C]= 0.650 M . The following reaction occurs and equilibrium is established:

A+2B⇌C

At equilibrium, [A] = 0.250 M and [C] = 0.850 M . Calculate the value of the equilibrium constant, Kc.

Answer 1

A    +      2B      <------------->   C

0.450        1.10                            0.650   ------------------> initial

0.450-x     1.10-2x                      0.650+x   ----------------> equilibrium

At equilibrium :

[A] = 0.450 - x = 0.250

x = 0.200

[B] = 1.10 - 2 x 0.200 = 0.700 M

Kc = [C] / [A][B]^2

     = (0.850)^2 / (0.250) (0.700)^2

     = 6.94

equilibrium constant, Kc. = 6.94