Redox reaction

Rusting of Iron Nails

Redox reaction – chemical reactions in which both oxidation and reduction occur simultaneously.
1) Oxidation

• gain of oxygen, O₂ by a substance
• loss of hydrogen, H₂ from a substance
• a loss of electrons
• occurs when there is an increase in oxidation number

2) Reduction

• loss of oxygen, O₂ by a substance
• gain of hydrogen, H₂ from a substance
• a gain of electrons
• occurs when there is an decrease in oxidation number

Oxidation Number – is the charge that the atom of the element would have if complete transfer of electron takes place.
IUPAC nomenclature – name inorganic compounds in order to avoid confusion due to elements have variable oxidation numbers.
Oxidation and Reduction in Terms of Gain and Loss of Oxygen
2CuO (s) + C (s) –> 2Cu (s) + CO₂ (g)

• Reduction:
  CuO loses its oxygen to form copper. CuO (oxidising agent) is being reduced.
• Oxidation:
  Carbon gains oxygen to form CO₂. Carbon (reducing agent) is said to be oxidised.

PbO (s) + CO (g) –> Pb (s) + CO₂ (g)

• Reduction:
  PbO loses its oxygen to form lead. PbO (oxidising agent) is being reduced.
• Oxidation:
  Carbon monoxide (CO) gains oxygen to form CO₂. Carbon monoxide (reducing agent) is said to be oxidised.

H₂ (g) + CuO (s) –> H₂O (l) + Cu (s)

• Reduction:
  CuO loses its oxygen to form copper. CuO (oxidising agent) is being reduced.
• Oxidation:
  Hydrogen (H₂) gains oxygen to form H₂O. Hydrogen (reducing agent) is said to be oxidised.

Oxidation and Reduction in Terms of Gain and Loss of Hydrogen
H₂S (g) + Cl₂ (g) –> S (s) + 2HCl (g)

• Reduction:
  Cl₂ gains hydrogen to form hydrogen chloride. Cl₂ (oxidising agent) is being reduced.
• Oxidation:
  Hydrogen sulphide loses hydrogen to form sulphur. Hydrogen sulphide (reducing agent) is said to be oxidised.

2NH₃ (g) + 3Br₂ (g) –> N₂ (g) + 6HBr (g)

• Reduction:
  Bromine gains hydrogen to form hydrogen bromide. Br₂ (oxidising agent) is being reduced.
• Oxidation:
  Ammonia loses hydrogen to form nitrogen. Ammonia (reducing agent) is said to be oxidised.