When aluminum (foil) is placed in an aqueous solution of copper(II) chloride, the aluminum atoms lose electrons to the copper(II) ions and replace them to form aluminum chloride, and to free up metallic copper.
The metallic copper has a tendancy to float on the surface of the solution, being buoyed by gas bubbles. The bubbles appear to evolve from the interface of the aluminum foil with the solution. What is the source and nature of the gas bubbles?
I have two hypotheses:
The bubbles are coming from dissolved $\ce{CO2}$ that is coming out of solution due to an increase in temperature close to the site of reactions.
The bubbles are $\ce{O2}$ bubbles coming from the layer of aluminum oxide on the surface of the aluminum foil.
If this is not the case, what happens to the portion of the portion of the foil that was in oxide form prior to the reaction. How would the aluminum oxide react with copper(II) chloride?