Good news. A moles-to-moles problems requires only one step.
14 mol O2 X 3 mol CO2 / 5 mol O2 = 8.4 mol CO2
In a moles-to-moles stoichiometry problem, the relevant coefficients in the balanced equation are used. The balanced equation shows us that 3 moles of carbon dioxide are produced for every 5 moles of oxygen gas that react. Therefore, to solve the problem, we should multiply the given 14 moles of oxygen gas by the ratio of 3 moles of carbon dioxide to 5 moles of oxygen gas shown in the balanced equation.