Consider the following reaction and associated equilibrium constant: a A( g )+ b
ID: 891822 • Letter: C
Question
Consider the following reaction and associated equilibrium constant:
aA(g)+bB(g)cC(g), Kc = 5.0
1. Find the equilibrium concentrations of A, B, and C for a=1, b=1, and c=2. Assume that the initial concentrations of A and B are each 1.0 M and that no product is present at the beginning of the reaction.
2. Find the equilibrium concentrations of A, B, and C for a=1, b=1, and c=1. Assume that the initial concentrations of A and B are each 1.0 M and that no product is present at the beginning of the reaction.
Explanation / Answer
1)
A(g) + B(g) ------------------> 2 C(g) Kc = 5.0
1.0 1.0 0
1.0 -x 1.0-x 2x
Kc = [C]^2 / [A] [B]
5.0 = (2x)^2 / (1-x)^2
2.24 = 2x / 1-x
2.24 - 2.24 x = 2x
x = 0.53
equilibrium concentrations of [A] = [B] = 1.0 - x = 1.0 - 0.53 = 0.47
[A] = [B] = 0.47 M
[C] = 2x = 2 x 0.53 = 1.06 M
2)
A(g) + B(g) ------------------> C(g) Kc = 5.0
1.0 1.0 0
1.0 -x 1.0-x x
Kc = [C] / [A] [B]
5.0 = x / (1-x)^2
x = 0.64
equilibrium concentrations of [A] = [B] = 1.0 - x = 1.0 - 0.64 = 0.36 M
[A] = [B] = 0.36 M
[C] = x = 0.64 M