Foundation reading 9 of 17 · ~5 min

Finish with whole-number coefficients

Your goal: Clear fractional coefficients and reduce the complete balanced equation.

A focused reading from Balancing Chemical Equations. Reading time is a Chem Help estimate.

Optional prerequisite review

Review if useful. These suggestions never lock a step.

Fractions are a legal intermediate

When a free diatomic element blocks you, a fractional coefficient such as 3/2 O₂ is a perfectly valid intermediate. Multiply the entire equation by the denominator at the end to clear it.

For combustion of C₂H₆ this gives 2 C₂H₆ + 7 O₂ → 4 CO₂ + 6 H₂O.

C₂H₆ + 7/2 O₂ → 2 CO₂ + 3 H₂O

Smallest whole numbers

An equation such as 4 H₂ + 2 O₂ → 4 H₂O is atom-balanced but not in lowest terms. Divide through by the greatest common divisor to get 2 H₂ + O₂ → 2 H₂O.

Grading systems, including the equation checker in the Question Bank, expect the reduced set.

Balanced but not reduced is still marked incomplete.

Sources and further reading

  • Chemistry 2e, Section 4.1: Writing and Balancing Chemical Equations
    Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson · OpenStax, Rice University · Chapter 4.1
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    Lesson-specific rights and provenance need review.

    The current online Chemistry 2e edition lists CC BY-NC-SA 4.0. The source version used for this lesson and its applicable rights remain unverified.

    Recorded use: reference. This describes the stored citation, not verified authorship or reuse permission.

    Recorded attribution / license claim (applicability unverified): Chemistry 2e, OpenStax, Rice University, licensed CC BY 4.0.

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  • General Chemistry bookshelf (LibreTexts)
    LibreTexts, University of California, Davis
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    Lesson-specific rights and provenance need review.

    The exact LibreTexts page and its license have not been established; the bookshelf citation does not grant permission for all linked material.

    Recorded use: further reading. This describes the stored citation, not verified authorship or reuse permission.

    Recorded attribution / license claim (applicability unverified): LibreTexts General Chemistry, licence varies by page, check the page footer.

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