Chlorine can be prepared by reacting potassium permanganate (KMNO4) with hydrochloric acid (HCl) in an aqueous solution.
The reaction is:
2KMNO4 + 3HCl → 2Cl2 + K2SO4 + 2MnCl2 + 4H2O
To increase the yield of chlorine, sulphuric acid (H2SO4) can be added to the reaction mixture. The reaction is then:
2KMNO4 + 3HCl + H2SO4 → 2Cl2 + K2SO4 + 2MnCl2 + 6H2O
This reaction is exothermic, meaning that it releases heat when it occurs.