Redox Reactions Lecture Notes

Introduction to Redox Reactions

• Redox Reactions: Simultaneous occurrence of oxidation and reduction.
• Oxidation: Gaining of oxygen or loss of electrons.
• Reduction: Loss of oxygen or gain of electrons.

Mnemonic for Redox Reactions

• OIL RIG: "Oxidation Is Loss, Reduction Is Gain" of electrons.

Examples

• Magnesium Atom:
  • Loses two electrons to become a 2+ ion (oxidized).
  • Gains two electrons to become neutral (reduced).

Redox Reactions

• Occur simultaneously, since electron loss by one substance necessitates gain by another.
• Redox: Combination of reduction and oxidation.

Example Reaction

• Magnesium + Dilute Acid (H⁺):
  • Magnesium: Loses two electrons, becomes Mg²⁺ (oxidized).
  • Hydrogen ions: Gain electrons, form hydrogen gas (reduced).

Displacement Reactions

• Involve a more reactive metal displacing a less reactive one.
• Reactivity Series Example:
  • Calcium + Iron Sulfate:
    • Calcium displaces iron, forming calcium sulfate.
    • Iron precipitates as a solid.

Ionic Equations

• Show particles that participate and change in the reaction.
• Spectator Ions: Do not change or participate by electron exchange, e.g., SO₄²⁻.

Half Equations

• Show the gain and loss of electrons for each element.
• Calcium Half Equation:
  • Calcium atom → Calcium 2+ ion + 2 electrons.
• Iron Half Equation:
  • Iron ion + 2 electrons → Iron atom.
• Ensure overall charge balance on each side.

Charge Balance in Half Equations

• Example with Iron:
  • Left: 2+ + 2(-1) = 0
  • Right: Neutral = 0
• If charges don't balance, electrons are on the wrong side.

Conclusion

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