Reaction of Halogens with Sodium Hydroxide

Chlorine + Sodium Hydroxide

Cl2 + 2NaOH → NaCl + NaOCl + H2O

Observation:

The greenish chlorine gas dissolves quickly in sodium hydroxide, forming a colourless solution.

Discussion:

Chlorine gas reacts with sodium hydroxide to form a salt of sodium chloride, sodium chlorate(I) and water.

    Bromine + Sodium Hydroxide

    Br2 + 2NaOH → NaBr + NaOBr + H2O

    Observation:

    The reddish-brown liquid bromine dissolves in sodium hydroxide, forming a colourless solution.

    Discussion:

    1. Bromine liquid reacts with sodium hydroxide to form a salt of sodium bromide, sodium bromate(I) and water.
    2. The reaction is less reactive compared with chlorine.

    Iodine + Sodium Hydroxide

    I2 + 2NaOH → NaI + NaOI + H2O

    Observation:

    The black iodine crystals dissolve slowly in sodium hydroxide, forming a colourless solution.

    Discussion:

    1. The reddish-brown liquid bromine dissolves in sodium hydroxide, forming a colourless solution.
    2. Solid iodine reacts slowly with sodium hydroxide to form a salt of sodium iodide, sodium iodate(I) and water.
    3. The reaction is least reactive among the three.

    Safety Precaution

    1. Fluorine, chlorine and bromine gases are poisonous.
    2. Therefore all the experiments involving these gases should be carried out in a fume chamber.
    3. The experiments involve fluorine are nor done in school.
    4. This is because fluorine is so reactive that it will react with most of the substance it comes into contact with.
    5. It is very difficult to conduct experiments involving fluorine.