Fire storm

Scattering sparks of fire occur in the flask after adding hot chromium (III) oxide powder

Scientific name: Oxidation of ammonia in the presence of chromium oxide

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Safety

Wear goggles and gloves. This experiment must be performed only in a fume hood.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

4NH3 + 5O2 → 4NO + 6H2O

2NO + O2 → 2NO2

Step-by-step instruction

WARNING! This experiment is dangerous! You should NOT perform this at home. ONLY carry out this experiment, if you are a trained chemist, and you understand local safety and legal requirements, which are required to perform such experiments

  1. You may use a concentrated ammonia solution or prepare ammonia gas by yourself. To prepare ammonia gas put sodium hydroxide and ammonia nitrate into a flask (in the ratio 1:1). Add a little water to the flask to initiate the reaction, and close it with a stopper with a gas-vent. Collect the produced ammonia into an inverted 1l flask (ammonia gas is lighter than air). After this close the flask filled with ammonia with a stopper. If you use ammonia solution, just pour about 100 ml of the solution into the flask and close it with a stopper.
  2. Make a crucible with a long metal handle (like a ladle). Put about 10 g of ammonium dichromate in a deflagrating spoon.
  3. Heat ammonium dichromate above a burner.
  4. When ammonium dichromate starts to decompose forming ammonium (III) oxide, lower the deflagrating spoon into to the flask with ammonium. Many sparks of fire occur in the flask after this. You also may heat purchasable chromium (III) oxide and spray it in the flask with ammonia.

Scientific background

Ammonium dichromate decomposes under heating producing chromium (III) oxide. Hot pieces of chromium (III) oxide are scattered sideways. It catalyzes the oxidation of ammonia with oxygen from air. In this reaction nitrogen oxide is produced, and then it is oxidized to nitrogen dioxide (a reddish-brown gas).

Danger:
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Difficulty:

Published on 01 April 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst