• # question_answer   How does $C{{u}_{2}}O$ act as both oxidant and reductant? Explain with proper reactions showing the change of oxidation numbers in each example.

$C{{u}^{+}}$ undergoes disproportionation to form $C{{u}^{2+}}$ and Cu. $2\,C{{u}^{+}}(aq)\xrightarrow{\,}\,C{{u}^{2+}}(aq)+Cu(s)$ Thus, $C{{u}^{+}}$ or $C{{u}_{2}}O$ acts both as an oxidant as well as a reductant (i) When heated in air,$C{{u}_{2}}O$ is oxidised to$CuO,$ $\overset{+1}{\mathop{C{{u}_{2}}}}\,\overset{-2}{\mathop{O}}\,\,+1/2\overset{0}{\mathop{{{O}_{2}}}}\,\xrightarrow{\,}\,2\overset{+2}{\mathop{Cu}}\,\,\overset{-2}{\mathop{O}}\,$ i.e., $C{{u}_{2}}O$ acts as a reductant and reduces ${{O}_{2}}$ to ${{O}^{2-}}$. (ii) When heated with $C{{u}_{2}}S,$ it oxidises ${{S}^{2-}}$ to $S{{O}_{2}}$ and hence$C{{u}_{2}}O$ acts as an oxidant $2\overset{+1}{\mathop{C{{u}_{2}}}}\,\overset{-2}{\mathop{O}}\,+\overset{+1}{\mathop{C}}\,{{u}_{2}}\overset{-2}{\mathop{S}}\,\xrightarrow{\,}\,6\overset{0}{\mathop{Cu}}\,+\overset{+4}{\mathop{S{{O}_{2}}}}\,$