1. The problem statement, all variables and given/known data Oxides of copper include CuO and Cu2O. In a crucible, you heat 1.51 g of one of these copper oxides in the absence of air and obtain 1.21 g of pure Cu. Which oxide did you have? 2. Relevant equations 3. The attempt at a solution I am really quite uncertain regarding how to even begin a problem like this.