Materials Needed
- 1 M solution of KI (potassium iodide) or NaI (sodium iodide)
- H cell (U-tube)
- Zinc electrode
- Carbon electrode
- Phenolphthalein indicator
- 2% starch solution
- Power supply
Procedure
Setup:
- Place the 1 M KI or NaI solution into both sides of the H cell.
- Add phenolphthalein and 2% starch solution to both sides of the H tube.
Electrode Connection:
- Attach the zinc and carbon electrodes to the respective sides of the H cell.
Current Activation:
- Turn on the power supply to initiate the current flow.
Observation:
- Observe the formation of a pink color at the cathode and a purple color at the anode.
Chemical Reactions
The following reactions occur during the demonstration:
| Half Reaction | Type | Equation |
|---|---|---|
| 2 H2O(l) + 2e− → H2(g) + 2 OH−(aq) | Cathode (reduction) | 2 H2O(l) + 2e− → H2(g) + 2 OH−(aq) |
| 2 I−(aq) → I2(l) + 2 e− | Anode (oxidation) | 2 I−(aq) → I2(l) + 2 e− |
| 2 I−(aq) + 2 H2O(l) → H2(g) + 2 OH−(aq) + I2(l) | Overall reaction | 2 I−(aq) + 2 H2O(l) → H2(g) + 2 OH−(aq) + I2(l) |
Conclusion
This demonstration illustrates the oxidation of iodide and highlights the roles of the cathode and anode in a galvanic cell. The color changes serve as visual indicators of the reactions occurring at each electrode.