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Redox reactions play a pivotal role in chemistry and biology.The values of standard reduction potential E^(@) of two half cell reaction decide which way the reaction is expected to proceed. A simple exaple is Danie cell in which zinc goes in to solution and copper gets deposited Given below are set of half cell reaction (acidic medium) along with their E^(@) values. I_(2)+2e^(-)rarr2I^(-) ""E^(@)=0.54 CI_(2)+2e^(-)rarr2CI^(-) ""E^(@)=0.54 Mn^(3+)+e^(-)rarrMn^(2+) ""E^(@)=1.36 Fe^(3+)+e^(-)rarrMn^(2+)""E^(@)=0.77 O_(2)+4H^(+)e^(-)rarr2h_(2)O""E^(@)=1.23 Using these data , obtain the correct explanation for the following question. Sodium fusion extact obvtined from aniline. On treatment with iron (II suphate and H_(2)SO_(4)) in presence of air givers a prussian blue precipitte.The blue colour is due to the formation of |
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Answer» `Fe_(4)[Fe(CN)_(6)]^_(3)` (Sodium FUSION extract) `Fe^(2+)+6CN^(-)rarr[Fe(CN)_(6)]^(4-)` In presence of AIR, `Fe^(2+)` ions get oxidised to `Fe^(3+)` ions. `(Fe^(2+)rarrFe^(3+)+E^(-)]xx4,E^(@)=-0.77V)` `(O_(2)+4H^(+)+4e^(-)rarr2H_(2)O,E^(@)=+1.23 V)/(4Fe^(2+)+4H^(+)+O_(2)rarr4Fe^(3+)+2H_(2)O)` `Fe^(3+)` ions then combine with `[Fe(CN)_(6)]^(4-)` ion to form FERRIC ferrocyanide which has prussian blue colour `4Fe^(3+)+3[Fe(CN)_(6)]^(4-)rarrFe_(4)[Fe(CN)_(6)]_(3)` |
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