Reaction of the Halogens with Iron Wool

Iron wool burns in differently colored gases.

Scientific name: Halogens react with iron according to their activity.

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Safety

This experiment should be performed only in a fume hood. Wear eye protection goggles and gloves.

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

Reaction formula

2Fe + 3Cl2 → 2FeCl3

2Fe + 3Br2 → 2FeBr3

Fe + I2 → FeI2

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. This experiment should be performed only in a fume hood.
  2. Fill the cylinder with chlorine gas.
  3. Cover the cylinder with a watch glass.
  4. Take a piece of iron wool with twisters and heat it with a gas burner.
  5. Put the wool into the cylinder.
  6. Iron reacts with chlorine producing brown fumes.
  7. Place a few drops of bromine into the test tube.
  8. Put the iron wool into the middle part of the test tube. Leave at least 2 cm between the substances.
  9. Fix the test tube on a stand. Clamp it near the top in a tilted position.
  10. Heat the test tube gently to let the bromine evaporate, then continue heating the iron wool.
  11. When the reaction begins and iron wool starts to glow remove heating.
  12. Place a few crystals of iodine into the test tube.
  13. Put the iron wool into the middle part of the test tube. Leave at least 2 cm between the substances.
  14. Fix the test tube on a stand. Clamp it near the top in a tilted position.
  15. Heat the test tube to sublime iodine. Keep heating until iodine vapors don’t reach the iron wool.
  16. The reaction is much less vigorous compared to the previous cases. The appearance of grey iron (ii) iodide is observed.

Scientific background

Iron reacts with halogens producing iron halides. Reactions are exothermic and make the iron wool burn and glow. The more active the halogen that takes part in the reaction the more vigor it passes. These reactions clearly show that the reactivity of halogens decreases down the group 7. On atomic level it means that the larger the radius of the halogen atom the less activity it possess. The most vigorous reaction could be expected in the case of fluorine. Components react even if both are cold and there is no additional heating. Reaction is very rapid. The white or pale green iron fluoride is formed. Chlorine is less reactive than fluorine but more reactive than bromine. Hot iron readily reacts with chlorine producing reddish-brown iron chloride. To make bromine interact with iron some extra heating is required. The iron will become coated with yellow-brown iron(III) bromide. Iodine is the least active and the reaction is much less vigorous compared to the previous cases. Heating of both components is required to start the reaction. Glowing is weak. Iodine cannot oxidize iron to +3 oxidation state. It canoxidize iron only as far as +2 oxidation state. The appearance of grey iron (II) iodide is observed

Danger:
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Published on 15 June 2015

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