Iodine Clock Reaction (Standard)

Purpose:

To demonstrate the relationship between a concentration and the rate of a chemical reaction.

Materials:

• 100mL graduated cylinder
• 10mL graduated cylinder
• 3 400mL beakers
• 50mL graduated cylinder
• 3 250mL beakers

Reagents:

• 0.2% Starch solution
• 0.2M Sodium metabisulfite (Na₂S₂O₅)
• 0.2M Potassium iodate (KIO₃)

Hazards and PPE:

• Potassium iodate is an oxidizer and toxin. Store and handle with care.
• Sodium metabisulfite is a serious toxin. Handle with care.
• Wear approved safety goggles and gloves.

Protocol:

Preparation

1. Prepare a series of solutions called Solution A according to the following chart using 400mL beakers:
   1. Beaker 1a: 50mL KIO₃ in 150mL DI H₂O.
   2. Beaker 1b: 100mL KIO₃ in 100mL DI H₂O.
   3. Beaker 1c: 25mL KIO₃ in 175mL DI H₂O.
2. Prepare 3 identical Solution 1-3B solutions by mixing 10mL of 0.2M Na₂S₂O₅ solution, 30mL starch solution, and 40mL DI H₂O in 250 mL beakers.

Demonstration

1. All at once, pour solutions 1-3B into 1-3A and stir.

Disposal:

• Solutions should be placed in a properly labeled waste container.

Reactions:

• The mechanism of the iodine clock reaction is unfortunately poorly understood.

Citations:

1. Summerlin, L. and Ealy, J. Chemical Demonstrations: A Sourcebook for Teachers, 1985.

Videos:

• Iodine Clock Reaction Chemical Experiment!

  Thoisoi2 - Chemical Experiments!