Chlorine

1
Chlorine
2
Chlorine and water

• Chlorine is added to domestic drinking water in
  order to kill and harmful bacteria or viruses
  which might be present.
• Less than 1 ppm (part per million) is needed to
  kill the bacteria.
• Because such a low concentration is used, you
  cannot taste the chlorine.

3

• Chlorine reacts with water to form an acidic
  solution which is a mixture of chloric(I) acid
  and hydrochloric acid
• Cl2 H2O ? HOCl HCl
• What is being oxidised and what is reduced?
• The chlorine is being oxidised and reduced at the
  same time.
• This is called a disproportionation reaction

4

• The chloric acid dissociates into H and OCl-.
• The OCl- is responsible for the bacteria-killing
  properties.
• Chlorine used to be added to swimming pools as a
  gas, but it was too dangeroius and corroded parts
  of the pool.
• Now it is added as chlorine compounds which
  dissolve to form chloric(I) acid.
• A concentration of about 6 ppm is used in
  swimming pools.

5
Chlorine and Sodium Hydroxide

• Cl2 2NaOH ? NaOCl NaCl H2O
• Using cold, aqueous NaOH
• These products are ionic (a metal and a non-metal
  in the compound)
• A mixture of chlorate(I) and chloride ions are
  formed.

6

• When the products are heated, the sodium chlorate
  disproportionates to form chlorate(V) ions and
  more chloride ions
• 3NaOCl ? NaClO3 2NaCl
• Sodium chlorate(I) is used as domestic bleach.
• It is also used in industry to bleach paper and
  fabrics.
• Sodium chlorate(V) is a powerful weed-killer.