Using the standard electrode potentials given in the table, predict if the reaction between the following is feasible:
Fe3+(aq) and I−(aq)
Ag+(aq) and Cu(s)
Fe3+(aq) and Cu(s)
Ag(s) and Fe3+(aq)
Br2(aq) and Fe2+(aq)
The possible reaction between Fe3+(aq)+I−(aq)
2Fe3+(aq)+2I−(aq)⟶Fe2+(aq)+I2(s) is given by,
Oxidation half equation: 2I−(aq)⟶I2(s)+2e−:E∘=−0.54 V
Reduction half equation: [Fe3+(aq)+e−⟶Fe2+(aq)]×2;E∘=+0.77 V
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2Fe3+(aq)+2I−(aq)⟶2Fe2+(aq)+I2(s);E∘=+0.23 V
E∘ for the overall reaction is positive. Thus, the reaction between Fe3+(aq) and I−(aq) is feasible.
The possible reaction between Ag+(aq)+Cu(s) is given by,
2Ag+(aq)+Cu(s)⟶Ag(s)+Cu2+(aq)
Oxidation half equation: Cu(s)⟶Cu2+(aq)+2e−:E∘=−0.34 V
Reduction half equation: [Al+(aq)+e−⟶Ag(s)]×2;E∘=+0.80 V
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2Ag+(aq)+Cu(s)⟶2Ag(s)+Cu2+;E∘=+0.46 V
E∘ positive for the overall reaction is positive. Hence, the reaction between Ag+(aq) and Cu(s) is feasible.
The possible reaction between Fe3+(aq) and Cu(s) is given by,
2Fe3+(aq)+Cu(s)⟶2Fe2+(s)+Cu2+(aq)
Oxidation half equation: Cu(s)⟶Cu2+(aq)+2e−:E∘=−0.34 V
Reduction half equation: [Fe3+(aq)+e−⟶Fe2+(s)]×2;E∘=+0.77 V
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2Fe3+(aq)+Cu(s)⟶2Fe2+(s)+Cu2+(aq);E∘=+0.43 V
E∘ positive for the overall reaction is positive. Hence, the reaction between Fe3+(aq) and Cu(s) is feasible.
The possible reaction between Ag(s) and Fe3+(aq)
Ag(s)+2Fe3+(aq)⟶Ag+(aq)+Fe2+(aq)
Oxidation half equation: Ag(s)⟶Ag+(aq)+e−:E∘=−0.80 V
Reduction half equation: Fe3+(aq)+e−⟶Fe2+(aq);E∘=+0.77 V
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Ag(s)+Fe3+(aq)⟶Ag+(aq)+Fe2+(aq);E∘=−0.03 V
Here, E∘ for the overall reaction is negative. Hence, the reaction between Ag(s) and Fe3+(aq) is not feasible.
The possible reaction between Br2(aq) and Fe2+(aq) is given by,
Br2(s)+2Fe2+aq⟶2Br−(aq)+2Fe3+(aq)
Oxidation half equation: Fe2+(aq)⟶Fe3+(aq)+e−×2:E∘=−0.77 V
Reduction half equation: Br2(aq)+2e−⟶2Br−(aq) ;E∘=+1.09 V
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Br2(aq)+2Fe2+(aq)⟶2Br−(aq)+2Fe3+(aq);E∘=−0.32 V
Here, E∘ for the overall reaction is positive. Hence, the reaction between Br2(aq) and Fe2+(aq) is feasible.