The
chemical reaction is represented as:
2A(g) = B(g) + C(g)
To determine the equilibrium concentration of A, we make use of the equilibrium
constant, Kc, given above. It is expressed as the ratio of the equilibrium
concentrations of the products and the reactants. For this reaction, it is
expressed as:
Kc = [B] [C] / [A]^2
From the problem statement, we are given the following
Kc = 0.035
Volume = 20.0 L
Initial concentrations: [B] = 8.00 mol / 20.0 L = 0.4 M
[C] = 12.00 mol / 20.0 L = 0.6
M
Since the initial reactants are B and C, the reaction is reversed as well as
the Kc.
Kc = [A]^2 / [B][C]
We use the ICE table:
B
C A
I 0.4 0.6
0
C -x -x
+x
------------------------------------------
E 0.4 - x 0.6 - x
x
Kc = x^2 / (0.4-x) (0.6-x) = 0.035
solve for x,
x = 0.07691 = [A]
