Percent Ionization Calculator
Determine what percentage of a weak acid ionizes in solution, based on its acid dissociation constant (Ka) and initial concentration.
What is percent ionization?
Percent ionization tells you what fraction of a weak acid’s molecules actually dissociate into ions in solution, rather than remaining as neutral acid molecules. Unlike strong acids, which ionize essentially completely, weak acids only partially ionize, and the extent depends on both Ka and the starting concentration.
How this calculator works
For a weak acid HA that ionizes as HA ⇌ H⁺ + A⁻, the equilibrium expression Ka = x² / (C₀ – x) is solved exactly using the quadratic formula, x = (-Ka + √(Ka² + 4·Ka·C₀)) / 2, where x is the equilibrium concentration of H⁺. Percent ionization is then x / C₀ × 100.
Note: This calculator solves the exact quadratic rather than the simplified approximation, so it stays accurate even for more concentrated or more strongly ionizing weak acids. Provided for general chemistry education and planning purposes.