Explain how you know it must be oxygen. Where did the oxygen come from?

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.

Explanation:

b. acid is the correct answer @jayxboof all social media

acid : acids are those which accepts an electron-pairs.

base : bases are those which donates ab electron-pairs.

alkali : it is a base that dissolves in water. it is basically a base and the ph greater than 7.

hydroxide ion : it is a poly-atomic ion which is negatively charged.

answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error