Oxides of copper include CuO and Cu₂O.You heat 1.51 g of one of these copper oxides in the absence of air and obtain 1.21 g of Cu.
True or false: You must have had CuO.

Question

Oxides of copper include CuO and Cu₂O.You heat 1.51 g of one of these copper oxides in the absence of air and obtain 1.21 g of Cu. True or false: You must have had CuO.

Quizplus · Accepted Answer

When CuO is heated in the absence of air, it decomposes to give copper metal and oxygen gas:
2CuO(s) → 2Cu(s) + O2(g)
From the balanced equation, it can be seen that the molar ratio of CuO to Cu is 2:2 or 1:1. Therefore, if you start with 1.51 g of CuO and completely convert it to Cu, you would expect to obtain 1.51 g of Cu. However, the actual yield is only 1.21 g of Cu. This means that not all of the CuO reacted to give Cu, indicating that the starting material was not pure CuO. 
Therefore, the only option that includes CuO in its composition is CuO itself. Hence, the answer is A.

Oxides of Copper Include CuO and Cu2O

Oxides of Copper Include CuO and Cu₂O