Question

When you burned copper, the product copper oxide appeared on the wire. Besides copper, the other reactant is oxygen, O2 . Explain how you know it must be oxygen. Where did the oxygen come from?

Answer 1

Copper oxide is the only product, and it contains copper and oxygen.

one of the reactants is copper, so the other reactant must be oxygen.

The copper metal must have combined with something in the air.

Answer 2

Answer:  The oxygen is coming from the atmosphere.

Explanation: After Nitrogen gas, the most abundant gas present in the atmosphere is oxygen gas which makes it available for the reaction.

The product which forms after the reaction between copper metal and oxygen gas is copper oxide which is a black color coating on the surface of the copper.

                          $2Cu(s)+O_{2}(g)\rightarrow 2CuO(s)$

When this copper oxide reacts with hydrogen gas, then the reaction among these two reactant gives copper metal and water as products.

                     $CuO(s)+H_{2}(g)\rightarrow Cu(s)+H_{2}O(g)$

From the above reaction, the formation of water shows that the oxyegn atom came from CuO.