SPM Chemistry

Reaction of Halogens with Metals

 Chlorine + Iron

3Cl2 + 2Fe → 2FeCl3

Observation

The iron wool burns vigorously with a bright flame, forming a brown solid after the reaction.

Discussion

  1. Chlorine reacts with iron to form brown iron(III) chloride.
  2. The reaction of potassium with concentrated hydrochloric acid produces chlorine gas.

2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 5Cl2 + 8H2O

Bromine + Iron

3Br2 + 2Fe → 2FeBr3

Observation

The iron wool glows brightly but less vigorously. A brown solid is formed.

Discussion

Bromine reacts with iron to form brown iron(III) bromide.

    Iodine + Iron


    3I2 + 2Fe → 2FeI3

    Observation

    The iron wool glows slowly with dim light. A brown solid is formed after the reaction.

    Discussion

    Iodine reacts with iron to form brown iron(III) iodide.

    Important Note

    1. Halogen is a reactive non-metal. It forms a salt when reacting with metals.
    2. The reactivity decreases down the group.
    3. Chlorine gas is poisonous. Excess chlorine gas is absorbed by the soda lime (sodium hydroxide) so that it does not escape to the surrounding.
    4. Iron wool rather than the iron piece is used to increase the rate of reaction.