By Sean Lancaster
Updated Aug 30, 2022

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Chemical equations are the language of chemistry—they describe how substances transform during a reaction. For straightforward transformations a single equation suffices, but complex processes often involve multiple steps. In such cases, chemists combine the individual half‑reactions into a single, balanced overall equation that captures every reactant and product.

Step 1 – Identify All Sub‑Reactions

List every half‑reaction, dissolution, precipitation, or displacement step that contributes to the final process. Each line represents a distinct portion of the chemistry.

Step 2 – Assemble the Total Reactant and Product Sides

Write all reactants on the left and all products on the right. For example, the redox transformation of iron and copper involves the half‑reactions:

Fe²⁺ → Fe³⁺ + e⁻ and Cu²⁺ + e⁻ → Cu⁺.

Adding them together gives:

Fe²⁺ + Cu²⁺ + e⁻ → Fe³⁺ + Cu⁺ + e⁻.

Step 3 – Cancel Common Species

Remove species that appear unchanged on both sides. In the example, the electron cancels out, leaving:

Fe²⁺ + Cu²⁺ → Fe³⁺ + Cu⁺.

Step 4 – Balance Mass and Charge

Ensure atoms and charges are balanced. For a non‑redox example:

Fe₂O₃ + Al → Al₂O₃ + Fe.

Balancing the atoms requires two aluminum atoms on each side and two iron atoms, yielding the final equation:

Fe₂O₃ + 2 Al → 2 Fe + Al₂O₃.