Hello! I really hope I get my post right this time because if not the rules are really hard to understand. 1. The problem statement, all variables and given/known data We did a lab the other day where copper(II)oxide reacts with carbon (charcoal powder) when adding heat from a bunsen burner. Our experiment was a success but I'm struggling with what our teacher said afterwards; that there can be two different reactions where two different solids form. We studied the product/products afterwards under a loupe and you could clearly see pure copper but also a lot of black solid something attached to the copper and it didn't look like charcoal because there were a small amount of leftovers which clearly looked like small pieces of charcoal, also they weren't attached to the copper. But according to the chemical equation the carbon should be excessive, does the charcoal carbon transform into some other form of carbon (besides the CO2)? 2. Relevant equations First reaction: 2CuO + C → 2Cu + CO2 This one I understand completely, this is called single replacement I think? The molar ratio is 2:1:2:1 amount of substances: nCuO = 0,025 moles nC = 0,021 moles C is excessive which means the theoretical exchange is 0,025 moles Cu and 0,0125 moles CO2, is this correct? Unfortunately we didn't think of weighing the product, the lab mainly was about collecting the CO2 and calculating the exchange percentage of real exchange divided by theoretical exchange. 3. The attempt at a solution I understand this is completely wrong but the rules have to be obeyed so here is my wild hypothesis for the second reaction: CuO + C + O2 → CuCO3 I know this is copper(II) carbonate and it should be green and it doesn't form from combustion but that's the only other reaction I can think of from the reactants.