Balancing Oxidation–Reduction (Redox) Reactions

Rucete ✏ Chemistry In a Nutshell

1. What Is a Redox Reaction?

• A redox reaction involves the transfer of electrons.
• Oxidation: loss of electrons
• Reduction: gain of electrons
• Both processes occur simultaneously.

2. Steps to Balance Redox Reactions in Acidic Solution

1. Separate into half-reactions (oxidation and reduction).
2. Balance all elements except H and O.
3. Balance oxygen using H₂O.
4. Balance hydrogen using H⁺.
5. Balance charge using electrons (e⁻).
6. Multiply half-reactions to equalize the number of electrons.
7. Add the two half-reactions and cancel anything that appears on both sides.

🔹 Example (acidic medium):

SO₃²⁻ + CrO₄²⁻ → SO₄²⁻ + Cr(OH)₃

Steps would include adding H₂O, H⁺, and e⁻ to balance O, H, and charge, then combining.

3. Steps to Balance Redox Reactions in Basic Solution

• Follow all steps for acidic solution, then:

8. Add OH⁻ to both sides to neutralize H⁺.
9. Combine H⁺ and OH⁻ into H₂O.
10. Simplify H₂O if needed by canceling.

🔹 Final balanced equation may include water and hydroxide ions (OH⁻).