Final answer:
Subscripts in a chemical formula indicate the number of atoms of each element in a molecule, while coefficients are used to balance the equation by indicating the number of each substance involved in the reaction.
Step-by-step explanation:
In a chemical formula, subscripts indicate the number of atoms of each element in a molecule. For instance, in water, H2O, the subscript '2' tells us there are two hydrogen atoms for every one oxygen atom. On the other hand, to balance chemical equations, we use coefficients which are placed in front of the formulas to indicate the quantity of molecules involved in a reaction.
This means while subscripts are part of the formulas and define the qualitative identity of substances (they are not changed after the chemical identity is determined), coefficients can be freely altered to balance the overall equation, ensuring that the number of atoms for each element is equal on both the reactant and product sides of the equation.
For example, when balancing an equation with water and hydrogen peroxide, changing the coefficient from H2O to H2O2 would result in a different chemical substance; however, adjusting the coefficient in front of H2O is proper to achieve balance.