Question

Making CO: Making CO from CO2 is a potential energy source. The value of Kp for the reaction CO₂ (g) + C (s) --> 2CO (g)    is 1.5 at 700C. Calculate the equilibrium partial pressures of CO and CO₂ if initially P_CO2 = 0.355 atm and P_CO= 5.30 atm. Pure granite is present intially and when equilibrium is achieved.

P_CO = _____ atm

P_CO2 = ______ atm

Answer 1

CO₂(g) + C(s)   <--------> 2CO(g)

Here, Kp = 1.5

We have,

Keq = (P_CO)²/P_CO2 = (5.3)²/0.355 = 79.12

Here, Kp< Keq, therefore backward reaction predominates

Let us assume the pressure of CO(g) at equilibrium = (5.3 - 2x)

Therefore, pressure of CO₂ at equilibrium = 0.355 + x

Now, Kp =1.5 = (5.3 - 2x)²/(0.355 + x)

4x² - 22.7x + 27.55 = 0

On solving,

x = 1.75

Equillibrium pressure of CO(g) = (5.3 - 2x) = (5.3 – 2 x 1.75) = 1.8 atm

Equillibrium pressure of CO₂ = 0.355 + x = 0.355 + 1.75 = 2.105 atm