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      H2O2 is the oxide of hydrogen.

Laboratory Preparation

H2O2 is prepared by the action of a cold dilute acid on a certain metallic peroxide e.g. BaO2, Na2O2.

BaO2(s) + H2SO4(aq)                  BaSO4(s) + H2O2(l)

Na2O2+  H2SO4(aq)                      Na2SO4(aq) + H2O2(aq)

Industrial Preparation of Hydrogen Peroxides by the oxidation of prapan-2-ol with oxygen under slight pressure.

(CH3)2 CHOH + O2(g)                                       (CH3)2 C = O(l) + H2O2(l)

Physical Properties

  • Pale-blue liquid (pure)
  • It freezes to a white crystalline solid at -0.90C
  • It boils with decomposition at 1500C
  • Dissolves in water to give a very weak acidic solution.

Chemical Properties

  1. On warming H2O2 give out oxygen.

2H2O2(l)                                       2H2O + O2(l)

  • H2O2 decomposes on exposure to air to form water and oxygen

2H2O2(l)                                       2H2O(l) + O2(l)

  • As an oxidizing agent.

H2O2 oxidizes lead(ii)sulphide PbS to lead(ii)tetraoxosulphate(vi)

PbS(s) + H2O2(aq)                                          PbSO4(s) + 4H2O(l)

– It reacts with acidified solution of potassium iodide to liberate free iodine

2KI + H2SO2 + H2O2(aq)                              K2SO4(s) +I2(s) + 2H2O(l)

  • H2O2 as a reducing agent

PbO2 +2H2O(l) PbO + 2H2O2(l) + 2O2

Ag2O + H2O2(l)                                          2Ag + H2O(l) + O2(g)

Uses of Hydrogen Peroxide

  1. H2O2 is used in bleaching of textile and wood pulp for paper making.
  2. It is used for water purification.
  3. It is used in the oxidation of dyestuffs in photography.
  4. It is used in production of porous concrete and foam in rubber.
  5. It is a useful antiseptic for the cleaning of the mouth and wounds.
  6. It is used in rockets and sub-marines.


Ozone is an allotropic form of oxygen. It is usually prepared  from oxygen by using silent electric discharge. Energy is introduced to oxygen at low temperature to prevent the unstable ozone from decomposing as soon as  it is formed. The apparatus consist of two conctric glass tubes lined with thin foil and arranged such that oxygen can pass through the space between them. The two terminals of an induction coil are connected to the tin foil on the two tubes respectively. The liberated gas is a mixture of ozone and oxygen called ozonised oxygen. The mixed ozone is liquefied to obtain nearly pure ozone. Oxygen boils off at -1830C leaving ozone, which boils at -1120C

Properties (Physical)

  1. It is a pale-blue gas, the liquid is obtained by liquefaction and it is deep/dark blue in colour.
  2. At low concentrations, the odour of ozone is pleasant, but at higher concentrations the odour is strong and unpleasant.
  3. It is extremely poisonous.
  4. The boiling point of ozone is -1120

Chemical Properties

It is a strong oxidizing agent oxidizes hydrogen sulphide to tetraoxosulphate(vi)acid, H2SO4.

H2S +  4O3(g)                    H2SO4(aq) + 4O2(g)

PbS + 4O3(g)                      PbSO4 + 4O2(g)

SO2(g) + O3(g)                    SO3(g) + O2(g)

Oxygen is more powerful oxidizing agent than oxygen, ozone decomposes to ordinary oxygen (O2) when heated or just allowed to stand.

2O3             heat    3O2(g)

             Test for Ozone

  • It has an odour similar to that of diluted chlorine.
  • It oxidizes mercury and leaves a trial of mercury stuck to the glass as the mercury flow across it.

  Uses of Ozone

  1. It is used to eliminate bad odour.
    1. It is used as a disinfectant to remove the undesirable odour and taste in water by killing the harmful bacteria.
    1. Ozone is used in bleaching.

EVALUATION:  How is hydrogen peroxide produced in the laboratory

ASSIGNMENT: Name two common air pollutants and give one source for each pollutant


                        State one air pollutant generated during the manufacture of fertilizers

                        Give two properties to distinguish oxygen from ozone.