Show that ''Law of conservation of mass is fully justified in a balanced chemical equation''.

Law of conservation of mass: The mass of reactants before the reaction is equal to the mass of products after the reaction.

Take the reaction;

$N_2+3H_2⟶2N{H}_3$

Mass of reactants= $28+3\left(2\right)=28+6=34$

Mass of products= $2\left(17\right)=34$

$\therefore$ Mass of reactants before reaction = Mass of products after reaction

$\therefore$ Law of mass conservation is fully justified in a balanced chemical equation.