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5% Approximation Rule in AP Chemistry

Verified for the 2027 exam
Verified for the 2027 exam•Fiveable Content Team

Definition

The 5% approximation rule is a guideline used in chemistry to simplify calculations involving weak acids and bases. It states that if the ionization of a weak acid or base is less than 5%, then the concentration of the un-ionized species can be approximated as equal to the initial concentration.

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AP course connection

Topic 7.7: Calculating Equilibrium Concentrations

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Unit 7

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