Redox Reactions Overview

Definition

• Redox reactions involve both oxidation and reduction occurring simultaneously.

Key Concepts

• Oxidation: Gaining of oxygen or loss of electrons.
• Reduction: Loss of oxygen or gain of electrons.

Mnemonic

• OIL RIG: "Oxidation Is Loss, Reduction Is Gain" (refers to electrons).

Examples

Aluminum and Oxygen Reaction

• Oxidation Example: Aluminum reacts with oxygen to form aluminum oxide.
• Reduction Example: Removal of oxygen from aluminum oxide.

Magnesium and Acid Reaction

• Magnesium loses two electrons to become Mg²⁺ (oxidized).
• Hydrogen ions (H⁺) gain electrons to form hydrogen gas (reduced).

Displacement Reactions

• Involve a more reactive metal displacing a less reactive one.
• Example: Calcium displaces iron from iron sulfate to form calcium sulfate, and iron is precipitated as a solid.

Writing Equations

Ionic Equations

• Show only particles that participate in the reaction and change.
• Spectator Ions: Ions that do not change (e.g., SO₄²⁻ in the calcium-iron reaction).

Half Equations

• Detail the gain and loss of electrons for each element involved.
• Example for Calcium:
  • Neutral Ca atom → Ca²⁺ ion + 2 electrons.
• Example for Iron:
  • Fe²⁺ ion + 2 electrons → Neutral Fe atom.

Balancing Charges

• Ensure total charge on both sides of the half-equation is equal.
• Check if charges balance to confirm correct placement of electrons.

Conclusion

• Redox reactions are fundamental to understanding chemical changes.
• Importance of understanding and writing balanced equations for clarity.

Note: Always check for charge balance in half-equations to prevent errors.