Reduction

Reduction is a chemical process in which a substance gains electrons, leading to a decrease in its oxidation state. In traditional chemistry, reduction was defined as the removal of oxygen from a compound, but in modern terms, it is understood as the gain of electrons.

Explanation of Reduction

Reduction is one part of a redox (reduction-oxidation) reaction, where one substance gains electrons (reduction), while another loses them (oxidation). The substance that gains electrons is called the oxidizing agent, as it causes another substance to be oxidized.

Key Aspects of Reduction

  1. Gain of Electrons (Primary Definition):
    • Example: Cu2++2e−→CuCu^{2+} + 2e^- \rightarrow CuCu2++2e−→Cu
    • Copper ions (Cu2+Cu^{2+}Cu2+) gain electrons and reduce to solid copper.
  2. Decrease in Oxidation Number:
    • Example: In Fe3+→Fe2+Fe^{3+} \rightarrow Fe^{2+}Fe3+→Fe2+, iron’s oxidation number decreases from +3 to +2.
  3. Removal of Oxygen (Traditional Definition):
    • Example: CuO+H2→Cu+H2OCuO + H_2 \rightarrow Cu + H_2OCuO+H2​→Cu+H2​O
    • Copper oxide (CuOCuOCuO) is reduced to copper by losing oxygen.
  4. Addition of Hydrogen (In Organic Chemistry):
    • Example: Reduction of an aldehyde to an alcohol: CH3CHO+2[H]→CH3CH2OHCH_3CHO + 2[H] \rightarrow CH_3CH_2OHCH3​CHO+2[H]→CH3​CH2​OH
    • The aldehyde gains hydrogen to form ethanol.

Examples of Reduction

  1. Rust Prevention (Iron Reduction):
    • Fe2O3+3CO→2Fe+3CO2Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2Fe2​O3​+3CO→2Fe+3CO2​
    • Iron ore is reduced to iron in a blast furnace.
  2. Photosynthesis (Biological Reduction):
    • 6CO2+6H2O+light→C6H12O6+6O26CO_2 + 6H_2O + \text{light} \rightarrow C_6H_{12}O_6 + 6O_26CO2​+6H2​O+light→C6​H12​O6​+6O2​
    • Carbon dioxide is reduced to glucose.
  3. Battery (Electrochemical Reduction):
    • Pb2++2e−→PbPb^{2+} + 2e^- \rightarrow PbPb2++2e−→Pb
    • Lead ions in a battery gain electrons and are reduced.

Importance of Reduction

  • Energy Storage: Used in rechargeable batteries.
  • Metallurgy: Extracting metals from ores.
  • Biological Processes: Essential in respiration and photosynthesis.
  • Chemical Industry: Used in hydrogenation and synthesis reactions.