Question

The reaction of iron(III) oxide with carbon monoxide is important in making steel. At 1000 K, Kp=19.9 for the reaction Fe2O3(s) + 3CO(g) <-----> 2Fe(s) + 3CO2(g). What are the equilibrium partial pressures of CO and CO2 if CO is the only gas present initially, at a partial pressure of 0.978 atm?

Answer 1

Solution :-

Balanced reaction equation

Fe2O3(s) + 3CO(g) <-----> 2Fe(s) + 3CO2(g).

In the Kp equation only gases state species are involved

Initial pressure of CO = 0.978 atm

Equilibrium pressured of CO and CO2 = ?

Kp=19.9

Lets make the ICE table

Fe2O3(s) + 3CO(g) <-----> 2Fe(s) + 3CO2(g).

                        0.978                                  0

                        -3x                                      +3x

                       0.978-3x                              3x

Kp = [CO2]^3 / [CO]^3

19.9 = [3x]^3/[0.978-3x]^3

19.9 = 27x^3 / [0.978-3x]^3

19.9* [0.978-3x]^3 = 27x^3

Solving this equation for the x

We get

X = 0.238

Therefore equilibrium pressure are as follows

[CO]eq = 0.978 atm – 3x = 0.978 atm – (3*0.238) = 0.264 atm

And

[CO2]eq = 3x = 3*0.238 atm = 0.714 atm