Answer:
By changing the coefficients you change the amount you have of certain compounds in the equation, whereas changing the subscript would change what compounds are actually in the equation because it would change the ratio of how many atoms of each element are in a compound.
For Example:
Outside of Balancing Equations, [tex]NO_{2}[/tex] (Nitrite) and [tex]NO_{3}[/tex] (Nitrate) are different because one forms a strong acid while the other forms a weak acid based on how many oxygen atoms are added to the compound. So in a chemical equation, if you change the subscripts, you change the entire compound so your reaction may be with a weak acid instead of a strong acid and give you a different product. Meanwhile, changing the coefficient changes the amount of the compound you have for the reaction in order to maintain the Conservation of Mass Law.
