Which statement best describes how the law of conservation of mass applies to chemical reactions?

• A. The mass of the products is always greater than the mass of the reactants due to energy release.
• B. The total mass of reactants equals the total mass of products in a chemical reaction.
• C. Only the mass of solids is conserved during chemical reactions; gases may escape.
• D. Mass can be created or destroyed during a chemical reaction.

Answer: (B)

Verified step by step guidance

1. Understand the law of conservation of mass: it states that mass cannot be created or destroyed in a chemical reaction.
2. Recognize that during a chemical reaction, atoms are rearranged but the total number of atoms remains the same.
3. Since atoms have mass, the total mass of all reactants before the reaction must equal the total mass of all products after the reaction.
4. Note that energy changes (such as energy release) do not affect the total mass in a measurable way in typical chemical reactions.
5. Conclude that the correct statement is that the total mass of reactants equals the total mass of products in a chemical reaction.