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Redox Reactions

Oxidation-reduction, oxidation states, balancing redox

Key Concepts
  • Oxidation: loss of electrons / increase in oxidation state
  • Reduction: gain of electrons / decrease in oxidation state
  • OIL RIG: Oxidation Is Loss, Reduction Is Gain
  • Oxidising agent: gets reduced; reducing agent: gets oxidised
  • Disproportionation: same element is simultaneously oxidised and reduced
Important Formulae
Balancing by half-reaction (acidic) Add H₂O to balance O, H⁺ to balance H, then balance charge
Oxidation state of O Usually −2 (except peroxides −1, OF₂ +2)
Oxidation state of H Usually +1 (except metal hydrides −1)
Quick Tips
  • F₂ is the strongest oxidising agent; Li is the strongest reducing agent.
  • In MnO₄⁻: Mn is +7; in Cr₂O₇²⁻: Cr is +6 — both are strong oxidisers in acidic medium.
  • Sum of oxidation states in a neutral compound = 0; in an ion = ion charge.
Sample Practice Questions

  1. Disproportionation reaction is one where the same element is:

    • Only oxidised
    • Only reduced
    • Both oxidised and reduced
    • Neither oxidised nor reduced
    Show answer

    Answer: Both oxidised and reduced

  2. Oxidation is defined as:

    • Gain of electrons
    • Loss of electrons
    • Gain of protons
    • Loss of protons
    Show answer

    Answer: Loss of electrons

  3. In the half-reaction: MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O, MnO₄⁻ is:

    • Reducing agent
    • Oxidising agent
    • Both
    • Neither
    Show answer

    Answer: Oxidising agent

  4. Oxidation state of oxygen in OF₂:

    • −2
    • −1
    • 0
    • +2
    Show answer

    Answer: +2

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Practice Questions

Practice 20 randomly selected NEET questions on Redox Reactions. Answers are revealed after each question.

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