Oxidation and reduction and redox reaction
The electronic structure of elements and the chemical reaction has given the classical conceptions of oxidation and reduction. The study of electrochemical reactions provides quantitative basics of oxidation and reduction reactions.
The reaction of magnesium metal burns in oxygen to produce magnesium oxide with the addition of oxygen. The reaction of magnesium metal with either oxygen or chlorine has led to the removal of two electrons from zerovalent magnesium metal forming magnesium(II) ion.
On the other hand, the lost electrons have found new homes in oxygen or chlorine forming the oxide or chloride ion.
It would thus appear the classical definition of oxidation and reduction has an intimate connection with redox definition.
What is an oxidation reaction?
Classically oxidation has defined as the combination of oxygen or any other electronegative element with another element or compound or as the removal of hydrogen or any other electropositive element from a chemical compound.
Combination of oxygen to carbon, magnesium, and iron
Carbon burns in oxygen to produce carbon dioxide. Here oxygen is combined with carbon to produce carbon dioxide and carbon is considered to have been oxidized.
C + O₂ ⇆ CO₂
Magnesium metal reacts with chlorine to produce magnesium chloride. In this reaction, magnesium is considered to have been oxidized because magnesium combines with oxygen to produced magnesium oxide.
2Mg + O₂ ⇆ 2MgO
Ferrous oxide heated in oxygen to produce ferric oxide. Here ferrous oxide is considered to have oxidized.
4FeO + O₂ ⇆ 2Fe₂O₃
Combination of electronegative chlorine
Chlorine gas passes through the colorless ferrous chloride solution it forms red ferric chloride. Ferrous chloride oxidized by the addition of electronegative element chlorine.
2FeCl₂ + Cl₂ ⇆ 2FeCl₃
Removal of hydrogen oxidation
Manganese dioxide reacts with concentrated hydrochloric acid to produce greenish-red chlorine gas.
4HCl + MnO₂ ⇆ MnCl₂ + Cl₂ + H₂O
Here hydrogen can remove from hydrogen chloride to form chlorine gas, hence the removal of hydrogen from hydrochloric acid indicated that hydrochloric acid can be oxidized.
Hydrogen sulfide reacts with chlorine to produce sulfur.
H₂S + Cl₂ ⇆ 2HCl + S
In the above reaction, hydrogen can remove from hydrogen sulfide. Thus hydrogen sulfide oxidized to form sulfur.
Removal of electro-positive elements
Potassium iodide reacts with hydrogen peroxide to produce iodine.
2KI + H₂O₂ ⇆ 2KOH + I₂
In the above reaction, electro-positive metal potassium can remove from potassium iodide to form iodine. Here potassium iodide oxidized.
What is the reduction reaction?
Classically reduction has defined as the combination of hydrogen or any other electropositive element with another element or compound or as the removal of oxygen or any other electronegative element from a chemical compound.
Addition of hydrogen reduction
Bromine can react with hydrogen to produce hydrogen bromide.
H₂ + Br₂ ⇆ 2HBr
In the above reaction, bromine can combine with hydrogen to produce hydrogen bromide and bromine can be reduced.
Hydrogen sulfide reacts with chlorine to produce hydrogen chloride and sulfur.
H₂S + Cl₂ ⇆ HCl + S
In the above reaction, chlorine can combine with hydrogen and reduced.
Addition of electro-positive elements
2K₃[Fe(CN)₆ + 2KOH + H₂O₂ ⇆ 2K₄[Fe(CN)₆] + 2H₂O + O₂
In the above reaction potassium ferricyanide combination with electro-positive element potassium to produce potassium ferrocyanide. Thus potassium ferricyanide can be reduced.
Removal of oxygen reduction
Hydrogen can pass through a black color heated cupric oxide, oxygen can remove from cupric oxide to form red color copper. Thus cupric oxide can be reduced.
CuO + H₂ ⇆ Cu +H₂O
Removal of electro-negative elements
Sulfur dioxide gas passes through a red ferric sulfate solution it turns greenish ferrous sulfate solution.
Fe₂(SO₄)₃ + 2SO₂ + H₂O ⇆ 2FeSO₄ + 2H₂SO₄
In the above reaction ferric sulfate removes sulfate to form ferrous sulfate. Thus ferric sulfate reduced to form ferrous sulfate.