As with any combustion reaction, the products of combusting a hydrocarbon fuel (cxhy) with oxygen (o2) are carbon dioxide (co2) and water (h2o). a mass of 16.55 g for an unknown fuel was combusted in a reaction vessel containing an unknown amount of oxygen. at the end of the reaction, there still remained 16.48 g of the fuel as well as 0.1144 g of water and 0.2096 g of carbon dioxide. the oxygen was completely consumed during the reaction. how many molecules of oxygen gas were initially present in the reaction vessel?