if we are looking at the combustion of methane we know that one molecule of methane can produce two water molecules that is what is dictated by the stochiometric coefficients because this ratio will hold true for any quantities of these substances it is also true that one mole of methane will produce two moles of water because a mole is just a number and since the number of items in a mole is equal to avagadro's number it is a simple matter to figure out the number of product molecules that are generated in a reaction by doing stochiometric calculations let's say we are looking at this exact scenario if one mole of methane combusts completely how many water molecules are produced well as we said due to the stochiometric ratio we know that 2 moles of water water are produced so how many molecules is that we simply multiply 2 moles by avagadro's number and we get 1.24 * 10 24 water molecules so we can quickly see that these calculations are just about utilizing a stochiometric ratio and avagadro's number in a twep process to give a number of product molecules let's try another example looking now at the combustion of hexane if three moles of hexane combust how many water molecules will be produced once again we need to find out the moles of water that are produced first which we can get by using the stochiometric ratio 3 moles of hexane times 10 moles of water for every 2 moles of hexane gives us 15 moles of water being formed then we simply multiply the number of moles by avagadro's number to get the number of water molecules that are produced so we've learned that for any reaction we can always go from the moles of a reactant to the moles of a product using the stochiometric ratio and then to the number of product molecules using avagadro's number