Question

Consider the following reaction:
A(g)⇌2B(g)
Find the equilibrium partial pressures of A and Bfor each of the following different values of Kp. Assume that the initial partial pressure of B in each case is 1.0 atm and that the initial partial pressure of A is 0.0 atm. Make any appropriate simplifying assumptions.

A) Kp= 1.6x10^-4

B) Kp=2.0X10^5

Answer 1

A (g) <----------------> 2 B (g)

0                                  1

+x                                1-2x

Kp = P²_B / P_A

1.6 x 10^-4 = (1-2x)^2 / x

1.6 x 10^-4x = 1 + 4x^2 - 4x

x = 0.50

P_A = 0.496 = 0.50 atm

P_B = 1 - 2x = 0.008 atm

b)

Kp = P²_B / P_A

2 x 10^5 = (1-2x)^2 / x

x = 5.0 x 10^-6

P_A = 5.0 x 10^-6 atm

P_B = 1 - 2x = 0.1 atm