Oxidation and Reduction in Chemistry

Oxidation and Reduction in Chemistry

  • Removal of hydrogen atom is oxidation while addition of hydrogen atom is reduction.
  • Addition of oxygen atom is oxidation while removal of oxygen atom is reduction.
  • Increase in valency of an element is oxidation while decrease in valency of an element is reduction.
  • Addition of an electronegative element is oxidation and removal is reduction.
  • Removal or electropositive element is oxidation and addition is reduction.
  • Loss of electrons is oxidation and gain of electrons is reduction.
  • Increase in oxidation number is oxidation while decrease in oxidation number is reduction.

Rules for Finding Oxidation Numbers :

  • Oxidation number of element in free state is zero i.e., P4 (oxidation number) ⇒ 0
  • Alkali metals (Na, K, Li, Cs etc.) and Alkaline earth metals (Ca, Mg, Ba, Sr etc.) have +1 and +2 oxidation number respectively.

General Studies Question Bank CD

  • Oxidation number of hydrogen is +1 except in metal hydride in which its oxidation number is -1. i.e., LiH (oxidation number of hydrogen atom) = 1
  • Oxidation number of oxygen atom is always equal to -2 except.
  • F2O (in this compound the oxidation number of oxygen is +2).
  • The oxidation number of oxygen atom in all peroxides is equal to -1.

Oxidizing and Reducing Agents

Compounds having higher oxidation number will be more acidic and act as oxidizing agent and compounds having lower oxidation number will be less acidic and act as reducing agent.

Generally, compounds with oxygen atom are called oxidizing agent and compounds with hydrogen atom are called reducing agent.

  • H2O2 acts as an oxidizing agent when it is reduced to H2O.
  • H2O2 acts as a reducing agent when it is oxidized to O2 or O3.
  • H2S acts as a reducing agent when it is oxidized to sulphur.
  • Halogens act as oxidizing agent and they are reduced to halogen acids.

General Studies Question Bank CD