Which statement explains how balanced chemical equations obey the law of conservation of mass?

• A. They show that the total mass of reactants equals the total mass of products.
• B. They indicate that energy is conserved during a chemical reaction.
• C. They ensure that the number of molecules is the same on both sides of the equation.
• D. They allow for the creation or destruction of atoms during a reaction.

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 a balanced chemical equation has the same number of each type of atom on both the reactant and product sides.
3. Know that because atoms are neither created nor destroyed, the total mass of the reactants must equal the total mass of the products.
4. See that balancing the equation ensures the quantities of atoms are conserved, which directly reflects the conservation of mass.
5. Conclude that balanced chemical equations demonstrate the law of conservation of mass by showing equal total mass before and after the reaction.