What is the relationship between mass of reactants and mass of products in a chemical reaction?
The mass of an atom is the sum of the masses of all of its protons and neutrons and the mass of the reactants is the sum of the masses of all of its atoms (protons and neutrons). Unless atoms are lost in the process, the mass of the products must equal the mass of the reactants if the process is stochiometric (all atoms participate in the reaction). Water (H2O) is produced by reacting hydrogen with oxygen and there must be exactly twice as many hydrogen atoms as oxygen atoms otherwise there will remain uncombined hydrogen or oxygen atoms (but no mass is lost). Of course the ‘product’ is that which you are trying to ‘produce’ and a complex reaction may also result in some unwanted products (or leftovers?).
