Chapter 16, Problem 98QAP

When a copper wire is exposed to air at room temperature, it becomes coated with a black oxide, CuO. If the wire is heated above a certain temperature, the black oxide is converted to a red oxide, Ct120. At a still higher temperature, the oxide coating disappears. Explain these observations in terms of the thermodynamics of the reactions
$\begin{array}{l}2\text{CuO}\left(s\right)\to {\text{Cu}}_2\text{O}\left(s\right)+\frac{1}{2}{\text{O}}_2\left(g\right)\\ {\text{Cu}}_2\text{O}\left(s\right)\to 2\text{Cu}\left(s\right)+\frac{1}{2}{\text{O}}_2\left(g\right)\end{array}$
and estimate the temperatures at which the changes occur.