Question
How does $Cu_2O$ act as both oxidant and reductant? Explain with proper reactions showing the change of oxidation numbers in each example.
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Answer
$Cu^+$ undergoes disproportionation to form $Cu^{2+}$ and $Cu$.
$2\text{Cu}^+(\text{aq})\xrightarrow{\ \ \ \ }\text{Cu}^{2+}(\text{aq})+\text{Cu}(\text{s})$
Thus, Cu+ or Cu2O acts both as an oxidant as well as reductant.
i.e. $Cu_2O$ acts as a reductant and reduces $O_2$ to $O^{2-}$.
$2\text{Cu}^+(\text{aq})\xrightarrow{\ \ \ \ }\text{Cu}^{2+}(\text{aq})+\text{Cu}(\text{s})$
Thus, Cu+ or Cu2O acts both as an oxidant as well as reductant.
- When heated in air, $Cu_2O$ is oxidised to $CuO$.
i.e. $Cu_2O$ acts as a reductant and reduces $O_2$ to $O^{2-}$.
- When heated with $Cu_2S$, it oxidises $S^{2-}$ to $SO_2$ and hence, $Cu_2O$ acts as an oxidant.
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$
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$
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$