How many grams of water are produced when 2.50 mol oxygen reacts with hydrogen?
Well calculate it out. You know that there are 6.02X10^23 atoms in a mole. You know that hydrogen has a GMW of 1.0 and oxygen has a GMW of 16. You know that water is H2O. You know, therefore how much a mole of water weighs. You also know that the specific gravity (in this case SG=Density) is 1 g/ml. Now you have all you need to know to derived the answer. We aren’t here to do your homework for you.