Group 7(17), the halogens (AS)

Uses of Chlorine and Chlorate(l)
Disproportionation: The halogen is reduced and oxidised at the same time.

Chlorine with Water:
Cl2(aq) + H2O(l) ⇌ HClO(aq) + HCl(aq)

In Sunlight:
2Cl2+ 2H2O → 4HCl + O2

Chlorination of Pools
NaClO(s)+ H2O(l)⇌ Na+ + OH-+ HClO(aq)undefinedundefined

Reaction of Chlorine with cold, dilute NaOH solution
Cl2(aq)+ 2NaOH(aq)→ NaCl(aq)+ NaClO(aq)+H2O(l)

The mixture of NaCl and NaClO is used as bleach to disinfect/kill bacteria.

The benefits to health of water treatment by chlorine outweigh its toxic effects.