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