To determine whether the reactions you've listed are feasible, we need to look at the standard electrode potentials (E°) for the half-reactions involved. The feasibility of a redox reaction can be assessed by calculating the cell potential (E°cell) using the formula:
E°cell = E°(reduction) - E°(oxidation)
When E°cell is positive, the reaction is spontaneous. Let's analyze each reaction step by step.
1. Fe3+(aq) and I–(aq)
The half-reactions are:
- Fe3+ + 3e– → Fe (E° = +0.77 V)
- 2I– → I2 + 2e– (E° = +0.54 V)
For this reaction, we will reduce Fe3+ and oxidize I–:
E°cell = E°(Fe3+/Fe) - E°(I2/I–) = 0.77 V - 0.54 V = +0.23 V
Since E°cell is positive, the reaction is feasible.
2. Ag+(aq) and Cu(s)
The half-reactions are:
- Ag+ + e– → Ag (E° = +0.80 V)
- Cu2+ + 2e– → Cu (E° = +0.34 V)
Here, we will reduce Ag+ and oxidize Cu:
E°cell = E°(Ag+/Ag) - E°(Cu2+/Cu) = 0.80 V - 0.34 V = +0.46 V
With a positive E°cell, this reaction is also feasible.
3. Fe3+(aq) and Cu(s)
The half-reactions are:
- Fe3+ + 3e– → Fe (E° = +0.77 V)
- Cu2+ + 2e– → Cu (E° = +0.34 V)
In this case, we will reduce Fe3+ and oxidize Cu:
E°cell = E°(Fe3+/Fe) - E°(Cu2+/Cu) = 0.77 V - 0.34 V = +0.43 V
Again, E°cell is positive, indicating that the reaction is feasible.
4. Ag(s) and Fe3+(aq)
The half-reactions are:
- Fe3+ + 3e– → Fe (E° = +0.77 V)
- Ag+ + e– → Ag (E° = +0.80 V)
Here, we will oxidize Ag and reduce Fe3+:
E°cell = E°(Fe3+/Fe) - E°(Ag+/Ag) = 0.77 V - 0.80 V = -0.03 V
Since E°cell is negative, this reaction is not feasible.
5. Br2(aq) and Fe2+(aq)
The half-reactions are:
- Br2 + 2e– → 2Br– (E° = +1.07 V)
- Fe2+ + 2e– → Fe (E° = -0.44 V)
In this case, we will reduce Br2 and oxidize Fe2+:
E°cell = E°(Br2/Br–) - E°(Fe2+/Fe) = 1.07 V - (-0.44 V) = 1.51 V
With a positive E°cell, this reaction is feasible.
Summary of Feasibility
- (a) Fe3+(aq) + I–(aq): Feasible
- (b) Ag+(aq) + Cu(s): Feasible
- (c) Fe3+(aq) + Cu(s): Feasible
- (d) Ag(s) + Fe3+(aq): Not feasible
- (e) Br2(aq) + Fe2+(aq): Feasible
By analyzing the standard electrode potentials and calculating the cell potentials, we can effectively predict the feasibility of these redox reactions. If you have any further questions or need clarification on any part, feel free to ask!
