PF1009 2024 12A Balancing Redox Equations PDF

## Balancing Redox Reactions ### Balancing Redox Reactions - Example 1 **Starting Equation:** SO₃^2- + MnO₄^- -> SO₄^2- + Mn²⁺ **Determine OX + Red species** **acidic Solution** **Redox reaction** **SO₃<sup>2-...

## Balancing Redox Reactions ### Balancing Redox Reactions - Example 1 **Starting Equation:** SO₃^2- + MnO₄^- -> SO₄^2- + Mn²⁺ **Determine OX + Red species** **acidic Solution** **Redox reaction** **SO₃^2- = sulfite** **SO₄^2- = sulfate** **Create Redox equations:** OX: SO₃^2- -> SO₄^2- Red: MnO₄^- -> Mn²⁺ **Balance metals (balance elements other than O and H initially)** OX: SO₃^2- -> SO₄^2- Red: MnO₄^- -> Mn²⁺ **Balance O with H₂O** OX: SO₃^2- + H₂O -> SO₄^2- Red: MnO₄^- -> Mn²⁺ + 4H₂O **Balance H with H⁺** OX: SO₃^2- + H₂O -> SO₄^2- + 2H⁺ Red: MnO₄^- + 8H⁺ -> Mn²⁺ + 4H₂O **Balance e^-:** OX: SO₃^2- + H₂O -> SO₄^2- + 2H⁺ + 2e^- Red: MnO₄^- + 8H⁺ + 5e^- -> Mn²⁺ + 4H₂O **Remove e^- from OX and Red** * (OX * 5) + (Red * 2) = 5SO₃^2- + 5H₂O + 2MnO₄^- + 16H⁺ + 10e^- -> 5SO₄^2- +10H⁺ + 10e^- +2Mn²⁺ + 8H₂O **Final equation:** 5SO₃^2- + 2MnO₄^- + 6H⁺ -> 5SO₄^2- + 2Mn²⁺ + 3H₂O **Verify** * **Mass balance:** = 5xS, 2xMn, 23xO, 6xH * **Charge balance:** = -6 both sides of equation. ### Balancing Redox Reactions - Example 2 **Cyanate** **Equation**: CN^- + MnO₄^- -> MnO₂ + OCN^- **Redox equations:** Skeletal Eq: OX: CN^- -> OCN^- Red: MnO₄^- -> MnO₂ **Redox reaction done in aq. base.** **OCN^- = cyanate** **Balance all atoms except O,H:** OX: CN^- -> OCN^- Red: MnO₄^- -> MnO₂ **Balance O wtih H₂O:** OX: CN^- + H₂O -> OCN^- Red: MnO₄^- -> MnO₂ + 2H₂O **Balance H with H⁺:** OX: CN^- + H₂O -> OCN^- + 2H⁺ Red: MnO₄^- + 4H⁺ -> MnO₂ + 2H₂O **Convert acidic to basic:** * Add sufficient H₂0 to each side of the equation. * For every H+ add OH- to the same side. * Add H2O to the opposite side. OX: CN^- + H₂O + 2OH^- -> OCN^- + 2H⁺ + 2OH^- Red: MnO₄^- + 4H⁺ + 4OH^- -> MnO₂ + 2H₂O + 4OH^- OX: CN^- + 2OH^- -> OCN^- + 2H₂O Red: MnO₄^- + 4H₂O -> MnO₂ + 2H₂O + 4OH^- OX: CN^- + 2OH^- -> OCN^- + H₂O + 2e^- Red: MnO₄^- + 2H₂O + 3e^- -> MnO₂ + 4OH^- **Balance charge with e^-:** * (OX * 3) + (Red * 2) = 3CN^- + 6OH^- + 2MnO₄^- + 4H₂O + 6e^- -> 3OCN^- + 3H₂O + 6e^- + 2MnO₂ + 8OH^- **Remove e^-:** 3CN^- + 6OH^- + 2MnO₄^- + 4H₂O -> 3OCN^- + 3H₂O + 2MnO₂ + 8OH^- **Final Equation:** 2MnO₄^- + 3CN^- + H₂O -> 2MnO₂ + 3OCN^- + 2OH^- **Verify if correct:** * **Charge balance:** -5 each side of equation * **Atoms balance:** * 2xMn * 3xC * 3xN * 9xO * 2xH **Each side of equation balanced.**