Genie in the bottle

decomposition reactions

Decomposition of 30% hydrogen peroxide with a catalyst.

Directions are courtesy of Flinn Scientific

Concepts:

Safety:

  • Safety glasses MUST be worn at all times by demonstrator and the audience.

  • Nitrile gloves, if you get on you skin it will destroy the tissue and turn it white.

  • The substance is severely corrosive to the skin, eyes and respiratory tract; a very strong oxidant; and a dangerous fire and explosion risk.

  • Do not heat 30% hydrogen peroxide.

  • Manganese dioxide may produce manganese metal, which is irritating as a dust or fume.

  • The reaction flask will get extremely hot; use only a Pyrex or borosilicate glass flask and hold with a towel around it to prevent burns.

  • Do not point the mouth of the flask towards yourself or anyone else. Never tightly close a vessel containing hydrogen peroxide—it may explode.

Equipment:

  • Hydrogen peroxide, H2O2, 30% ( Flinn demo kit )

  • 50 mL Graduated cylinder.

  • 50-mL or 100-mL Manganese dioxide

  • MnO2, 5 g (Or KI)

  • Volumetric flask, Pyrex®1000-mL

  • Filter paper or tissue

Preparation:

  1. 1. Wrap 4–5 g of manganese dioxide in a small piece of filter paper or tissue.

  2. Staple the filter paper so that no solid leaks out.

  3. Add 50 mL of the 30% hydrogen peroxide solution to a 1000-mL Pyrex volumetric flask. Caution: Wear rubber gloves when handling 30% H2O2. Contact with skin may cause burns.

Demonstration Instructions

  1. Set the flask on a counter and hold the flask with a thick cloth towel. Drop in the manganese dioxide packet. Make sure the flask is upright and that all students are a safe distance away.

  2. A “magic genie” (water droplets and oxygen gas) will emerge from the flask.

  3. The flask will get extremely hot.

  4. The towel will hide the flask contents as well as protect your hand from the heat produced.

Observations:

Learning Outcomes:

  • Hydrogen peroxide, 30%, will act as an oxidizing agent with practically any substance. It decomposes to produce oxygen gas. Here is where you can use your 4-gas instrument to demonstrate oxygen enriched environments.

  • You can also talk about decomposition reactions and products and how to monitor for those products. This happens a lot in fires with chemical involvement.

  • This can lead into homemade explosives with H2O2

Chemical Disposal:

  • Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Filter the mixture to retrieve the spent catalyst, which may be packaged for landfill disposal according to Flinn Suggested Disposal Method #26a. The remaining liquid may be flushed down the drain with excess water according to Flinn Suggested Disposal Method #26b.

Additional Information:

  • If done in a large mouth container a lit splint can be extinguished and then put into the oxygen enriched atmosphere and it will reignite.