According to the Law of Conservation of Mass, which quantity or quantities must always be the same on both sides of a balanced chemical equation?

• A. The total mass of all reactants and products
• B. The total number of molecules
• C. The total energy released or absorbed
• D. The total volume of gases

Answer: (A)

Verified step by step guidance

1. Understand the Law of Conservation of Mass, which states that mass cannot be created or destroyed in a chemical reaction.
2. Recognize that in a balanced chemical equation, the total mass of the reactants must equal the total mass of the products.
3. Note that while the number of molecules, energy changes, or volume of gases can vary, the total mass remains constant.
4. Therefore, the quantity that must always be the same on both sides of a balanced chemical equation is the total mass of all reactants and products.
5. This principle ensures that the equation is balanced in terms of atoms and mass, reflecting the conservation law.