Answer
The subscripts in a chemical formula cannot be fractions. The coefficients in a balanced chemical equation cannot be fractions. Changing the subscripts to balance is unacceptable because we are changing the compounds or substances which the reaction details.
Work Step by Step
The subscripts cannot be fractions as we cannot have part of an atom to be bonded in a compound. Similarly, coefficients cannot be fractions as we cannot have part of a compound used in a reaction. Changing the subscripts to balance is unacceptable because we are then outlining a completely different reaction with different reactants and products. In other words, when we change the subscripts, we change the substances in the reactants and products and therefore describe a completely different reaction.
