Copper Oxidation-Reduction
2Cu + O₂ → 2CuO (Oxidation)
CuO + H₂ → Cu + H₂O (Reduction)
Brown copper powder → Black copper oxide → Brown copper
Zinc Oxide Reduction
ZnO + C → Zn + CO
ZnO is reduced / Carbon is oxidized
Zinc oxide loses oxygen, carbon gains oxygen
Manganese Dioxide with HCl
MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O
MnO₂ is reduced / HCl is oxidized
MnO₂ loses oxygen, HCl loses hydrogen
Iron Oxide Reduction
Fe₂O₃ + 3CO → 2Fe + 3CO₂
Fe₂O₃ is reduced / CO is oxidized
Used in iron extraction from ore
Hydrogen Oxidation
2H₂ + O₂ → 2H₂O
Hydrogen is oxidized
Hydrogen gains oxygen to form water
Combustion (Complete Oxidation)
CH₄ + 2O₂ → CO₂ + 2H₂O
Methane is completely oxidized
Both carbon and hydrogen gain oxygen
🔑 Key Concepts to Remember
What is a Redox Reaction?
A redox (reduction-oxidation) reaction is a chemical reaction where one substance gets oxidized while another gets reduced simultaneously. These reactions always occur together - you cannot have oxidation without reduction!
OIL RIG Memory Aid
Oxidation Is Loss (of electrons/hydrogen or gain of oxygen)
Reduction Is Gain (of electrons/hydrogen or loss of oxygen)
Activity 1.11 - What We Observed
When copper powder is heated in air, it gains oxygen and turns black (oxidized to CuO). When hydrogen gas is passed over this black copper oxide while heating, it loses oxygen and returns to brown copper (reduced back to Cu). The hydrogen itself gets oxidized to water. This demonstrates that oxidation and reduction happen together in redox reactions.
Identifying Oxidation and Reduction
A substance is OXIDIZED if it:
✓ Gains oxygen
✓ Loses hydrogen
A substance is REDUCED if it:
✓ Loses oxygen
✓ Gains hydrogen
Real-World Applications
• Rusting: Iron oxidizes in presence of moisture and oxygen
• Respiration: Glucose is oxidized to release energy
• Photosynthesis: Water is oxidized, CO₂ is reduced
• Batteries: Redox reactions produce electrical energy
• Metallurgy: Metal ores are reduced to extract pure metals
• Bleaching: Uses oxidizing agents to remove color