Problem 15 - Chemistry An Atoms First Approach

Question

Can the subscripts in a chemical formula be fractions? Explain. Can the coefficients in a balanced chemical equation be fractions? Explain. Changing the subscripts of chemicals can balance the equations mathematically. Why is this unacceptable?

Step-by-Step Solution

Answer

Subscripts in a chemical formula cannot be fractions, as they represent the number of atoms in a compound, which are indivisible. However, coefficients in a balanced chemical equation can be fractions, indicating the ratio of amounts for each substance. Nevertheless, whole numbers are usually preferred for convenience. Changing subscripts to balance equations is unacceptable, as it alters the compounds' identity.

Step 1: Subscripts as fractions

No, subscripts in a chemical formula cannot be fractions. The reason is that subscripts represent the number of atoms of a particular element present in a chemical compound. Since atoms are indivisible entities and cannot exist as fractions, subscripts must be whole numbers.

Step 2: Coefficients as fractions

Yes, coefficients in a balanced chemical equation can be fractions. Coefficients represent the number of moles (or molecules) of a particular compound involved in the reaction. Fractions can be used to balance an equation, as it indicates the ratio of amounts for each substance in the reaction. In practice, it is usually more convenient to use whole number coefficients by multiplying all coefficients by the least common denominator to eliminate fractions.

Step 3: Unacceptability of changing subscripts

Changing the subscripts of chemicals in a chemical formula may mathematically balance the equation, but it is scientifically unacceptable because doing so would change the identity of the compounds involved in the reaction. The subscript numbers determine the proportions of atoms in the compound, and altering them would lead to a different compound instead of balancing the original reaction. In summary, subscripts in a chemical formula cannot be fractions as they represent the number of atoms, which are indivisible entities. Coefficients in a balanced chemical equation can be fractions to indicate the ratio of amounts for each substance, although whole numbers are often preferred for convenience. Lastly, changing subscripts is unacceptable for balancing equations because it alters the identity of the involved compounds.