# Chemical Equilibrium Problem

1. Sep 15, 2010

### zorro

1. The problem statement, all variables and given/known data
At a certain temperature, the equilibrium constant for the gaseous reaction of CO with O2 to produce CO2 is 5000 lit/mole. Calculate [CO] at equilibrium, if 1 mol each of CO and O2 afre placed in a 2 L vessel and allowed to come to equilibrium.

2. Relevant equations

3. The attempt at a solution

Concentration at equilibrium
CO= 1-x
O2= 1-x/2
CO2=x where x is the no of moles dissociated

Kc=x^2/(1-x)^2(1-x/2)=5000

I dont understand what assumption I should make to solve this.

2. Sep 15, 2010

### Staff: Mentor

I have not tried to solve, so it is possible there will be some more hurdles, but first step is more or less obvious - equilibrium is shifted far to the right, so amount of product is almost stoichiometric.

I have a gut feeling that it will be better to approach the question from the other end - assume you started with 1 mole of CO2 and half mole of oxygen. x will be very small then and approximations will be much more obvious.

Last edited by a moderator: Aug 13, 2013
3. Sep 15, 2010

### zorro

As you said I took 1 mole CO2 and half mole O2
and got x value as 0.058 (moles of CO)
But how do we relate this the problem (1 mole CO and 1 mole O2)

4. Sep 15, 2010

### Staff: Mentor

Through stoichiometry. If total amount of substances present is identical, it doesn't matter if you start with products or reactants, equilibrium is the same.

Last edited by a moderator: Aug 13, 2013