Question

Oxygen in the air combines with the copper statue to form copper oxide, which is green. Which of these is the correct chemical reaction for this? A) Cu + O → CuO Eliminate B) Cu + O2 → CuO C) CuO → Cu + O2 D) 2 Cu + O2 → 2CuO

Answer 1

D, 2Cu + O2 → 2CuO. A is wrong because oxygen is a diatomic element, meaning it always has to come in the form of O2 in the case of gas. B is wrong because the equation isn't balanced correctly; there's two oxygens on the reactants side, while only one oxygen on the products side. C is wrong because it's saying you're STARTING OUT with CuO already: that doesn't correspond with the word problem. Thus leaves D, where the equation is balanced correctly, has the diatomic oxygen, and ends with CuO.