Question

Consider the following reaction and associated equilibrium constant:
aA(g)⇌bB(g), Kc = 3.7

A) Find the equilibrium concentrations of A and B for a=1 and b=1. Assume that the initial concentration of A is 1.0 M and that no B is present at the beginning of the reaction.

B) Find the equilibrium concentrations of A and B for a=2 and b=2. Assume that the initial concentration of A is 1.0 M and that no B is present at the beginning of the reaction.

C) Find the equilibrium concentrations of A and B for a = 2 and b = 1. Assume that the initial concentration of A is 1.0 M and that no B is present at the beginning of the reaction.

Answer 1

aA(g) <----> bB(g) ; Kc = 3.7

A)

when a = 1 and b = 1 then,

          A <-----> B

Initially 1         0

change        -x        +x

at equilib (1-x)     (0+x)

Kc = [B]/[A]

3.7 = (x)/(1-x)

x = 0.7872

[B] = 0.7872 M

[A] = (1-0.7872) = 0.2128 M

B)

when a = 2 and b = 2 then,

           2A <-----> 2B

Initially    2*1         2*0

change        -2x        +2x

at equilib (2-2x)     (0+2x)

Kc = [B]/[A]

3.7 = (2x)/(2-2x)

x = 0.7872

[B] = 0.7872 M

[A] = (1-0.7872) = 0.2128 M

C)

when a = 2 and b = 1 then,

           2A <-----> B

Initially       2*1         0

change      -2x        +x

at equilib (2-2x)     (0+x)

Kc = [B]/[A]

3.7 = (x)/(2-2x)

x = 0.881M

[B] = 0.881 M

[A] = (1-0.881) = 0.119 M