Redox reactions involve the transfer of electrons between reactants, resulting in both oxidation and reduction occurring simultaneously. Oxidation is defined as either the loss of electrons or gain of oxygen. Reduction is defined as either the gain of electrons or loss of oxygen. Common examples of redox reactions in daily life include combustion, corrosion/rusting, photosynthesis, and respiration.

1. Redox Reactions What is the meaning of REDOX? R E D O X Ox idation Red uction

2. Examples of Redox Reactions which occur in daily life Combustion Corrosion/Rusting Photosynthesis Respiration

4. Defn 1 (In terms of oxygen) Oxidation = addition/gain of oxygen A substance that gains oxygen is said to be oxidised. Reduction = removal/loss of oxygen. A substance that loses oxygen is said to be reduced.

5. Example based on Defn 1 (In terms of oxygen) Zn + PbO -> ZnO + Pb Zinc (Zn) is oxidised because it gains oxygen to form zinc oxide . Lead (II) oxide (PbO) is reduced because it loses oxygen to form lead . When one substance is oxidised, another substance must be reduced. Oxidation and reduction take place at the same time. Such reactions are called REDOX reactions.

6. Example based on Defn 1 (In terms of oxygen) 2. Fe 2 O 3 + 3CO -> 2Fe + 3CO 2 Carbon monoxide (CO) is oxidised. Iron (III) oxide (Fe 2 O 3 ) is reduced.

7. Defn 2 (In terms of hydrogen) Oxidation = removal/loss of hydrogen A substance that loses hydrogen is said to be oxidised. Reduction = addition/gain of hydrogen. A substance that gains hydrogen is said to be reduced.

8. H 2 S + Cl 2 -> 2HCl + S The substance oxidised is h ydrogen sulfide (H 2 S) because it loses hydrogen to form sulfur . The substance reduced is c hlorine (Cl 2 ) because it gains hydrogen to form hydrogen chloride . 2. CH 4 + Cl 2 -> CH 3 Cl + HCl Substance oxidised is methane (CH 4 ). Substance reduced is chlorine (Cl 2 ). Example based on Defn 2 (In terms of hydrogen)