Conservation of mass is the underlying principle of balancing equation. When we balance equation, this means that we acknowledge that before and after the chemical reaction, the elements are conserved. To balance the chemical equation, we add coefficients before each reactant and product. Here are the following answers:
Reaction 1:
2Al
3ZnCl2
3Zn
2AlCl3
Reaction 2:
4NH3
3O2
2N2
6H2O
