Which statement about balanced equations is true?

• A. It shows equal numbers of atoms of each element on both sides.
• B. It shows only products.
• C. It is always written with words.
• D. It does not involve atoms.

Answer: (A)

Balancing shows the conservation of mass in chemical reactions—the same number of each type of atom must appear on both sides of the equation. By using coefficients in front of reactants and products, we adjust the counts so the atoms match on both sides. This is exactly what the statement about equal numbers of atoms on each side is getting at, so it’s the best description. For example, 2 H2 + O2 → 2 H2O has four hydrogen atoms and two oxygen atoms on both sides. The other ideas don’t fit: a balanced equation includes both reactants and products, not only products; it uses chemical symbols and formulas, not just words; and atoms are involved because their counts must be preserved.