When balancing a chemical equation, which of the following must be true?

• A. The number of atoms of each element must be the same on both sides of the equation.
• B. The charges of all compounds must be zero on both sides of the equation.
• C. The total number of molecules must be the same on both sides of the equation.
• D. The coefficients of all reactants must be equal to the coefficients of all products.

Answer: (A)

Verified step by step guidance

1. Understand that balancing a chemical equation means ensuring the law of conservation of mass is obeyed, which states that matter cannot be created or destroyed in a chemical reaction.
2. Recognize that this requires the number of atoms of each element to be the same on both sides of the equation, so no atoms are lost or gained during the reaction.
3. Note that the charges of compounds do not necessarily have to be zero on both sides; rather, the total charge should be balanced if dealing with ionic equations.
4. Understand that the total number of molecules does not have to be the same on both sides; coefficients can differ as long as atom counts are balanced.
5. Realize that coefficients of reactants do not have to be equal to coefficients of products individually; they must be adjusted to balance atoms, not necessarily to be equal.