Final answer:
Among the provided options, equations a (CaCO₃ → CaO + CO₂) and b (Fe₂O₃ + 3H₂ → 2Fe + 3H₂O) are balanced. However, equations c (Al + 3Br₂ → AlBr₃) and d (H₂O + 2O₂ → H₂O₂) are not balanced and need correction to adhere to the law of conservation of matter.
Step-by-step explanation:
To determine if a chemical equation is balanced, we must ensure that the number of atoms for each element is the same on both the reactant and product sides, in accordance with the law of conservation of matter. Let's analyze the provided equations.
- a) CaCO₃ (s) → CaO (s) + CO₂ (g) is balanced: 1 Ca on both sides, 1 C on both sides, and 3 O on both sides.
- b) Fe₂O₃ (s) + 3H₂ (g) → 2Fe (s) + 3H₂O (l) is balanced: 2 Fe on both sides, 3 O on both sides, and 6 H on both sides.
- c) Al (s) + 3Br₂ (l) → AlBr₃ (s) is not balanced; the correct balanced equation should be 2Al + 3Br₂ → 2AlBr₃.
- d) H₂O (l) + 2O₂ (g) → H₂O₂ (l) is also not balanced; the correct equation is 2H₂O + 2O₂ → 2H₂O₂ or H₂O + O₂ → H₂O₂ for a simpler balanced version.