Chemistry
General Knowledge

Oxidation & Reduction



Oxidation & Reduction ( old concept )

Oxidation

Oxidation is a process which involves either of the following —
(i) addition of oxygen
(ii) removal of hydrogen
(iii) addition of electro negative element or group
(iv) removal of electro positive element or group.

        2Mg + O2 → 2MgO (oxidation of Mg)
        H2S + Cl2 → 2HC1 + S (oxidation of H2S)
        Fe + S → FeS (oxidation of Fe)
        2KI + H2O2 → 2KOH + I2 (oxidation of KI)

Reduction

Reduction is a process which involves either of the following —
(i) addition of hydrogen
(ii) removal of oxygen
(iii) addition of electro positive element or group.
(iv) removal of electronegative element or group.

        H2 + Cl2 → 2HC1 (reduction of Cl2)
        CuO + C → Cu + CO (reduction of CuO)
        HgCl2 + Hg → Hg2Cl2 (reduction of HgCl2)
        2FeCl3 + H2 → 2FeCl2 + 2HC1 (reduction of FeCl3)

Modern concept of oxidation and Reduction

According to modern concept, loss of electrons is called oxidation whereas gain of electrons is called reduction.

        Na → Na+ + e (oxidation of Na)
        Zn → Zn2+ + 2e (oxidation of Zn)
        Cl2 + 2e → 2C1- (reduction of Cl2)
        S + 2e → S2- (reduction of S)

Oxidising agent (O.A.)

A substance which undergoes reduction is called oxidising agent

        CuO + C → Cu + CO
        Oxidation - C, Reduction- CuO,
        Oxidising agent - CuO

Examples — O2, O3, H2O2, KMnO4, K2Cr2O7 etc.

Reducing agent (R. A.)

A substance which undergoes oxidation is called reducing agent.

        H2O + C → CO + H2
        Oxidation— C, Reduction— H2O
        Reducing agent — C

Examples — H2, CO, H2S, SO2, C, SnCl2, etc.

Redox Reaction

A reaction in which both oxidation and reduction takes place simultaneously is called redox reaction.

Examples — CuO + C → Cu + CO
Oxidation — C, Reduction — CuO