Chlorine + Water
Cl2 + 2H2O → HCl + HOCl
- Chlorine gas dissolves in water to form a pale yellow solution.
- The solution turn blue litmus paper red before it is bleached.
- The solution formed is acidic and contains bleaching agent.
- Hypochlorous(I) acid is a strong bleaching agent. It decolourises the colour of litmus paper.
Bromine + Water
Br2 + 2H2O → HBr + HOBr
- Bromine liquid dissolves slowly in water to form a yellowish-brown solution.
- The solution turn blue litmus paper red before it is bleached slowly.
Hypobromous(I) acid is a weak bleaching agent.
Iodine + Water
I2 + 2H2O → HI + HOI
- Only a little iodine dissolves in water to form a yellowish solution.
- The solution turns blue litmus paper red but does not bleach it.
Hypoiodous(I) acid has very weak bleaching characteristic.
- Chlorine, bromine and iodine are soluble in water to form an acidic solution.
- The solubility decreases down the group.
- Aqueous chlorine and bromine are a bleaching agent.
- Aqueous iodine does not act as a bleaching agent.
- Chlorine gas is produced through the following reaction:
2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 5Cl2 + 8H2O