Practical No. 04: Determination of Electrode Potential of Copper
XIII. Interpretation of Results
Electrochemical cell with zinc and copper electrodes produced measurable EMF. Copper’s reduction potential was calculated using cell potential and known oxidation potential of zinc, matching the standard value of +0.34 volts. Zinc is placed above copper in electrochemical series.
XIV. Conclusions and Recommendations
- Conclusion: Zinc is more electropositive than copper (lower reduction potential -0.76 V vs +0.34 V). Hence zinc undergoes corrosion in preference to copper when in contact.
- Recommendation: Clean electrode surfaces, use fresh solutions, and ensure proper connections for accurate readings.
XV. Practical Related Questions & Answers
Q1. Describe the chemical reactions at the cathode and anode in the experiment.
- Answer:
- At Anode (Zinc electrode – oxidation): Zn → Zn²⁺ + 2e⁻ (Zinc loses electrons and dissolves as Zn²⁺ ions).
- At Cathode (Copper electrode – reduction): Cu²⁺ + 2e⁻ → Cu (Copper ions gain electrons and deposit as copper metal on the electrode).
- Net Reaction: Zn + Cu²⁺ → Zn²⁺ + Cu.
Q2. Explain the relation between the reduction electrode potential of a metal electrode and its tendency towards corrosion.
- Answer: Lower reduction potential indicates a higher tendency to undergo oxidation (corrosion). Metals with more negative reduction potentials (like Zn, Fe) have a higher tendency to lose electrons and corrode. Metals with positive reduction potentials (like Cu, Ag) have a lower tendency to corrode. Thus, more electropositive metals corrode preferentially.
Q3. Identify the cathode and anode in the given electrochemical cell.
- Answer: Zinc electrode acts as the Anode (negative terminal) where oxidation occurs. Copper electrode acts as the Cathode (positive terminal) where reduction occurs. Electrons flow from zinc (anode) through the external circuit to copper (cathode), and conventional current flows from copper to zinc.
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