concentration of O2 at equilibrium

Question

consider the following unbalanced equation at some constant temperature:

CO2(g) CO(g) + O2(g) where K = 4.1 x 10^-6

in an experiment, 5.8 mol of CO2 and 2.8 mol of CO are initially placed into a 1.0L rigid container. Calculate the concentration of O2 when the reaction has reached equilibrium.

Answer 1

First, balance the equation and set up an ICE table...

2CO2(g) <==> 2CO(g) + O2(g)

5.8mol............2.8mol......0.....Initial

-x..................+x..........+1/2x...Change

5.8-x.........2.8+x.........1/2x....Equilibrium

Keq = [CO]²[O₂]/[CO₂]²

4.1x10^-6 = (2.8+x)²(0.5x)/(5.8-x)²

4.1x10^-6 = 0.5x³ + 2.8x² + 3.9^x/x² = 11.6x + 33.6

Solve for x and multiply by 2 to get the final O2 concentration at equilibrium.