The formation of water according to the equation 2H2 + O2 + 2H20
shows that 2 molecules (made of 4 atoms) of hydrogen and 1 molecule (made of 2 atoms) of
oxygen produce 2 molecules of water. The total mass of the product, water, is equal to the sum of
the masses of each of the reactants, hydrogen and oxygen. What parts of Dalton's atomic theory are
illustrated by this reaction? What law does this reaction illustrate?