You always balance the equation first, which is done. Set up a proportion: the answer comes out of the balanced equation. 6 mols O2:4 mols CO2:: x : 0.3020 mols CO2 6/4 = x / 0.3020 You could reduce this, but why bother. Calculators to the rescue. Cross multiply 0.3020 *6 = 4*x 1.812 = 4x Divide by 4 1.812/4 = x x = 0.4530 to 4 places. D <<<< answer