Electrolysis of Potassium Iodide
Description: When a 0.5 M Potassium Iodide solution is electrolyzed, water is reduced at the cathode to form hydroxide ions. Hydrogen gas is generated by at the cathode from hydronium ions in solution. This raises the pH at the cathode. The color change in the phenolphthalein is used to track the reduction. Iodide ion (I–) is oxidized at the anode. Iodide forms Iodine(aq), which is observed by its characteristic brown color in aqueous solution. Starch solution may be used as an indicator for this oxidation. It will form a deep blue colored complex with the iodine solution.
Source: UW Card Catalog
Year: N/A Vol: N/A Page: N/A
Keywords: Oxidation, Reduction, Cathode, Anode, Electrolysis, Indicators
Rating: 
Hazard: Medium
- Acute toxicity hazard – specific organ -thyroid
- Flammability hazard
- Germ cell mutagenicity hazard
- Reproductive toxicity hazard
- Carcinogenicity hazard
- Electrocution hazard
Effectiveness: Good
- Results are clearly observable without guidance
- Good connection from demo to course material
- High reliability
- Time to results is low
- Mild effects are seen by audience
Difficulty: Medium
- Some concerted or timed manipulations
- Reactions or demos at non-standard conditions
- Use of scientific equipment
- Some intermediate steps to results
Safety Precautions:
- Eye protection required
- Gloves required
- UL approved three-prong plug and outlet required
- Perform in a well-ventilated area
- Absorbent materials on hand
- Use of chemically resistant surface is recommended
- Avoid inhalation or exposure to any vapors, mists, or droplets
- Avoid contact with live electrodes
Class: Electrochemistry, Electrolysis, Redox, Indicators
Division: General, Analytical Chemistry, Physical Chemistry
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