question_answer

An iron rod is immersed in a solution containing \[1.0\,M\,NiS{{O}_{4}}\] and \[1.0\,M\,ZnS{{O}_{4}}\] . Predict giving reasons which of the following reactions is likely to proceed? (i) Fe reduces \[Z{{n}^{2+}}\] ions, (ii) Iron reduces \[N{{i}^{2+}}\] ions. Given: \[E{{{}^\circ }_{Z{{n}^{2+}}/Zn}}=-0.76\,V,\]\[E{{{}^\circ }_{F{{e}^{2+}}/Fe}}=-0.44\,V\] \[and\,\,\,{{E}^{{}^\circ }}_{N{{i}^{2+}}/Ni}=-0.25V\]                                                  

Answer:

                (i) Since \[E{}^\circ \] of Zn is more negative than that of Fe, therefore, Zn will be oxidised to \[Z{{n}^{2+}}\] ions while \[F{{e}^{2+}}\] ions will be reduced to Fe. In other words, Fe will not reduce \[Z{{n}^{2+}}\] ions. (ii) Since \[E{}^\circ \] of Fe is more negative than that of Ni, therefore, Fe will be oxidized to \[F{{e}^{2+}}\] ions while \[N{{i}^{2+}}\] ions will be reduced to Ni. Thus, Fe reduces \[N{{i}^{2+}}\] ions.