Which of the following indicates that a chemical equation is balanced?

• A. The sum of the masses of reactants is less than the sum of the masses of products.
• B. The total number of molecules is the same on both sides of the equation.
• C. The number of atoms of each element is the same on both sides of the equation.
• D. The coefficients of all reactants and products are equal.

Answer: (C)

Verified step by step guidance

1. Understand the Law of Conservation of Mass, which states that matter cannot be created or destroyed in a chemical reaction. This means the total mass of reactants must equal the total mass of products.
2. Recognize that a balanced chemical equation must have the same number of atoms of each element on both sides of the equation to satisfy this law.
3. Note that the sum of the masses of reactants being less than the sum of the masses of products violates the conservation of mass, so this cannot indicate a balanced equation.
4. Understand that having the same total number of molecules on both sides does not guarantee the equation is balanced because molecules can contain different numbers of atoms.
5. Realize that coefficients of all reactants and products being equal is not necessary; coefficients must be adjusted to ensure the number of atoms of each element is equal on both sides.