7. The standard emf (E°cell) is calculated using the formula:
E°cell = E°cathode - E°anode
Here, Fe²⁺/Fe is the cathode (reduction) and Al³⁺/Al is the anode (oxidation).
E°cell = (-0.44 V) - (-1.66 V) = +1.22 V
The cell reaction is:
2Al(s) + 3Fe²⁺(aq) → 2Al³⁺(aq) + 3Fe(s)
8. A salt bridge is a device used in electrochemical cells to maintain electrical neutrality by allowing ion flow between half-cells. Its functions are:
- To complete the electrical circuit by permitting ion migration.
- To prevent accumulation of charge in either half-cell, which would stop the reaction.
- To maintain charge balance as electrons flow through the external circuit.
9. i) Mg(s) | Mg²⁺(aq) || Al³⁺(aq) | Al(s)
Anode (oxidation): Mg(s) → Mg²⁺(aq) + 2e⁻
Cathode (reduction): Al³⁺(aq) + 3e⁻ → Al(s)
Balanced cell reaction: 3Mg(s) + 2Al³⁺(aq) → 3Mg²⁺(aq) + 2Al(s)
ii) Zn(s) | Zn²⁺(aq) || Ag⁺(aq) | Ag(s)
Anode (oxidation): Zn(s) → Zn²⁺(aq) + 2e⁻
Cathode (reduction): Ag⁺(aq) + e⁻ → Ag(s)
Balanced cell reaction: Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s)
10. For the reaction: Sn²⁺(aq) + Cu(s) → Sn(s) + Cu²⁺(aq)
E°cell = E°cathode - E°anode
Here, Sn²⁺/Sn is the cathode and Cu²⁺/Cu is the anode.
E°cell = E°Sn²⁺/Sn - E°Cu²⁺/Cu = (-0.136 V) - (0.34 V) = -0.476 V
Since E°cell is negative, the reaction is not feasible under standard conditions.
Parent Tip: Review the logic above to help your child master the concept of oxidation reduction reactions worksheet.
