Redox intro
- 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
- 3. 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.
- 4. 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.
- 5. 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.
- 6. 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.
- 7. 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)