28.2.10—Calculations: other redox systems

For any supplied redox pair, identify oxidation and reduction, balance each half-equation, cancel electrons and use the resulting mole ratio for calculations.

Use E° or the stated conditions to choose direction, then verify mass and charge conservation. Unfamiliar species do not require a new method.

If X²⁺ + 2e⁻ → X and Y → Y³⁺ + 3e⁻, the least common electron number is six, giving 3X²⁺ + 2Y → 3X + 2Y³⁺.

Do not force a familiar coefficient pattern onto a new oxidation state or calculate mass before finding the electron ratio.