question_answer 76)

  In question 34, write redox couples involved in the reactions (i) to (iv).

Answer:

  (i) \[Cu+Z{{n}^{2+}}\to C{{u}^{2+}}+Zn\] \[E_{\operatorname{Re}dox\,process}^{{}^\circ }=E_{\operatorname{Re}duced\,species}^{{}^\circ }-E_{Oxidised\,species}^{{}^\circ }\]                 \[=E_{Z{{n}^{2+}}/Zn}^{{}^\circ }-E_{C{{u}^{2+}}/Cu}^{{}^\circ }\]                 \[=(-0.76)-(+0.34)=-1.10V\] Negative value shows that the redox process is not feasible. (ii)   \[Fe+C{{d}^{2+}}\to Cd+F{{e}^{2+}}\]                        \[E_{\operatorname{Re}dox\,process}^{{}^\circ }=E_{\operatorname{Re}duced\,species}^{{}^\circ }-E_{Oxidised\,species}^{{}^\circ }\]                                 \[=E_{C{{d}^{2}}/Cd}^{{}^\circ }-E_{F{{e}^{2+}}Fe}^{{}^\circ }\]                                 \[=(-0.40)-(-0.44)=+0.04V\] Positive value shows that the redox process is feasible.