Now, let's suppose we react 1 mol of methane with two moles of oxygen, and we find that our actual yield in grams was 38 grams of carbon dioxide. Now, if we find our theoretical yield, we could then find our percent yield. How would we go about finding our theoretical yield? Well, we have to realize that we have 1 mol reacting in two moles. That means a theoretical yield of this guy is 1 mol. Because one to two gives you one of this guy and two of this guy.