Answer: The atom count for each element on the reactant side of a balanced chemical equation is equal to the atom count for each element on the product side of the same equation
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products formed must be equal to the mass of reactants taken.
In order to get the same mass on both sides, the atoms of each element must be balanced on both sides of the chemical equation.
Thus there are 4 atoms of hydrogen on reactant as well as product side.
Also there are 2 atoms of oxygen on reactant as well as product side.