11th Class Chemistry Redox Reactions Question Bank 11th CBSE Chemistry Redox Reactions

  • 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.

    Answer:

                    \[C{{u}^{+}}\] 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 \[2\overset{+1}{\mathop{C{{u}_{2}}}}\,\overset{-2}{\mathop{O}}\,+\overset{+1}{\mathop{C}}\,{{u}_{2}}\overset{-2}{\mathop{S}}\,\xrightarrow{\,}\,6\overset{0}{\mathop{Cu}}\,+\overset{+4}{\mathop{S{{O}_{2}}}}\,\]


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