Electrochemical Cell Potentials

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🎯 WALT & Success Criteria

We Are Learning To: Calculate standard cell potentials and predict the spontaneity of electrochemical reactions

Success Criteria - I can:

✓ Use standard reduction potentials to calculate cell potentials

✓ Predict whether a reaction is spontaneous using E°cell values

✓ Explain how concentration changes affect cell potentials

✓ Connect electrochemical principles to real-world applications

📚 Key Concepts

Remember: E°cell = E°cathode - E°anode

Spontaneous reactions: E°cell > 0

Mātauranga Māori Connection: Traditional Māori understanding of mauri (life force) in materials relates to electron flow and energy transfer in electrochemical cells.

🔋 Part 1: Standard Cell Potential Calculations

1. Given the standard reduction potentials: Cu²⁺ + 2e⁻ → Cu (E° = +0.34 V) and Zn²⁺ + 2e⁻ → Zn (E° = -0.76 V). Calculate the standard cell potential for a Cu-Zn cell.

2. Which half-reaction occurs at the cathode in the Cu-Zn cell above?

Cu²⁺ + 2e⁻ → Cu

Zn²⁺ + 2e⁻ → Zn

Cu → Cu²⁺ + 2e⁻

Zn → Zn²⁺ + 2e⁻

3. Predict whether this reaction is spontaneous: Ag⁺ + Cu → Ag + Cu²⁺

Given: Ag⁺ + e⁻ → Ag (E° = +0.80 V), Cu²⁺ + 2e⁻ → Cu (E° = +0.34 V)

4. Extension Challenge: Calculate the cell potential for: 2Al³⁺ + 3Mg → 2Al + 3Mg²⁺

Given: Al³⁺ + 3e⁻ → Al (E° = -1.66 V), Mg²⁺ + 2e⁻ → Mg (E° = -2.37 V)

🌊 Part 2: Real-World Applications & Concentration Effects

5. A car battery uses the reaction: Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O. What happens to the cell potential as the battery discharges and H₂SO₄ concentration decreases?

Cell potential increases

Cell potential decreases

Cell potential remains constant

Cell potential becomes negative

6. Kaitiakitanga Connection: How do electrochemical principles apply to environmental protection? Choose all that apply:

Galvanic protection of metal structures

Electroplating to prevent corrosion

Battery recycling to recover metals

Electrochemical water treatment

7. Explain how the Nernst equation shows that cell potential depends on concentration. Use the relationship between mauri (life force) and electron flow in your explanation.

8. Design Challenge: Design an electrochemical cell using New Zealand materials (consider metals found in our geology). Calculate the theoretical cell potential and explain one practical application.