Practical No. 06: Determination of Voltage Generated from Chemical Reaction using Daniel Cell
XIII. Interpretation of Results
Daniel cell generated approximately 1.1 volts under standard conditions. Voltage changed with variations in electrolyte concentrations, following Nernst equation. Higher Cu²⁺ concentration near cathode and lower Zn²⁺ concentration near anode increased the voltage.
XIV. Conclusions and Recommendations
- Conclusion: Voltage depends on electrolyte concentrations, with maximum voltage at maximum concentrations.
- Recommendation: Clean electrodes, use fresh salt bridge, and ensure tight connections for accurate voltage measurement.
XV. Practical Related Questions & Answers
Q1. Identify the anode and cathode in a Daniel cell.
- Answer: In a Daniel cell, Zinc electrode (Zn) acts as the Anode (negative terminal) where oxidation occurs. Copper electrode (Cu) acts as the Cathode (positive terminal) where reduction occurs. Electrons flow from zinc anode through the external circuit to copper cathode.
Q2. Describe the chemical reactions occurring at the cathode and anode in the experiment.
- Answer:
- At Anode (Zinc): Zn → Zn²⁺ + 2e⁻ (Oxidation).
- At Cathode (Copper): Cu²⁺ + 2e⁻ → Cu (Reduction).
- Net reaction: Zn + Cu²⁺ → Zn²⁺ + Cu.
- Observation: The zinc dissolves, and copper deposits on the copper electrode.
Q3. Elaborate on the concept of a half cell.
- Answer: A half cell is a single electrode immersed in a solution of its own ions. It consists of a metal electrode and an electrolyte solution containing the corresponding metal ions. When two half cells are connected, they form an electrochemical cell. Each half cell has its own electrode potential, and the combination of two half cells gives the total cell potential.
Q4. Explain the function of a salt bridge or porous pot in the electrochemical cell.
- Answer: The salt bridge maintains electrical neutrality by allowing the flow of ions between the two half cells. It prevents the accumulation of excess positive charges near the anode and negative charges near the cathode. It completes the electrical circuit and allows the continuous flow of electrons in the external circuit, maintaining the cell potential.
Q5. Name the electrolytes suitable for incorporation into a salt bridge.
- Answer: Suitable electrolytes for a salt bridge include:
- (i) KCl (Potassium chloride)
- (ii) KNO₃ (Potassium nitrate)
- (iii) Na₂SO₄ (Sodium sulphate)
- (iv) NH₄NO₃ (Ammonium nitrate)
- Note: The ions should not react with the electrode solutions and should have similar ionic mobilities.
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