The combustion of 0.374 kg of methane in the presence of excess oxygen produces 0.983 kg of carbon dioxide. what is the percent yield?

Assuming that it undergoes complete combustion, all of the carbons from methane would be converted to carbon dioxide. Thus you would be able to know the % yield of product by converting everything first to moles then dividing the product with the reactant. The moles of methane is 0.023375 while the moles of carbon dioxide is 0.02234. In calculating for the % yield divide the moles of CO2 with moles of methane and you would get 95.58%. 

it would only be the stuff in module eight so you need to study all the lessons in that you also could check the flvs

hope this : )