Uses of Chlorine

• Water treatment: (swimming pools, drinking water)

  Cl2(g) + H2O(l) -> HCLO(aq) + HCl(aq)

  Redox- disproportional Cl is reduced and oxidised

  Chloric(1)acid is an oxidising agent- kills bacteria by oxygenating

  other halogens react more slowly down the group
• Alternative to direct chlorination:

  NaClO(s) + H2O(l) -> Na+(aq) + OH-(aq) + HClO(aq)


  In alkaline, equilibrium shifts to the LHS, HClO removed as ClO- ions

  to prevent- keep pools slightly acidic
• Reaction with alkali:

  CL2(g) + 2NaOH(aq) -> NaClO(aq) + NaCl(aq) + H2O(l)


  Redox- disproportional

  Cl and cold dilute NaOH -> oxidising agent NaClO which is an active ingredient in household bleach

  other halogens react similarly
• Benefits of water treatment

  • Water treatment kills harmful bacteria.
  • The increased cancer risk is small, but a cholera epidemic would kill thousands.
  • Some people complain about this forced mass medication, but this prevents thousands of deaths every year and on balance is good for society.