<u>Answer: </u>The coefficient '2' must be added infront of and in order to balance a chemical reaction.
<u>Explanation:</u>
Law of conservation of mass states that the mass can neither be created nor be destroyed, but it can only be transformed from one form to another. It always remain conserved.
In a chemical reaction, the number of individual atoms on the reactant side must be equal to the number of individual atoms on the product side. All the balanced chemical reactions follow law of conservation of mass.
For the given chemical reaction, the balanced equation follows:
<u>On reactant side:</u>
Number of potassium atoms = 2
Number of nitrogen atoms = 2
Number of oxygen atoms = 6
<u>On product side:</u>
Number of potassium atoms = 2
Number of nitrogen atoms = 2
Number of oxygen atoms = 6
Thus, the coefficient '2' must be added infront of and in order to balance a chemical reaction.