chemistry

IDEAS OF OXIDATION AND REDUCTION

The term oxidation was first used to describe chemical reactions in which oxygen was added to an element of a compound. The phenomenon of combustion was the earliest example of oxidation. Later on the term oxidation was extended to describe many more reactions which occurred without the use of even oxygen

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Addition of oxygen:

        2Mg + O*2 = 2MgO               (Oxidation of magnesium)

        S + O*2 = SO2                      (Oxidation of sulphur)

        2CO + O*2 = 2CO2                (Oxidation of carbon monoxide)

        Na2SO3 + H2O*2 = Na2SO4 + H2O (Oxidation of sodium sulphite)

Removal of hydrogen 

        H2S + Cl*2 = 2HCl + S             (Oxidation of hydrogen sulphide)

        4HI + O*2 = 2H2O + 2I2          (Oxidation of hydrogen iodide)

        4HI + MnO*2 = MnCl2 + 2H2O + Cl2 (Oxidation of hydrogen chloride)

Addition of an electronegative element:

        Fe+ S* = FeS                       (Oxidation of iron)

        SnCl2 + Cl*2 = SnCl4              (Oxidation of stannous chloride)

        2Fe + 3F*2 = 2FeF3               (Oxidation of iron)

Removal of an electropositive element:

        2KI + H2O*2 = 2KOH + I2                (Oxidation of potassium iodide)

        2K2MnO4 + Cl*2 = 2KCl + 2KMnO4     (Oxidation of potassium manganate)

        2KI + Cl*2 = 2KCl + I2                     (Oxidation of potassium iodide)

A substance which brings oxidation is known as oxidizing agent. The substances marked with asterisk sign(*) in above equations are oxidizing agents.