Degree of Dissociation Calculator

How it works

Ka = c·α² ÷ (1 − α) (→ α ≈ √(Ka/c) when small); α = Λ/Λ°; α = (i − 1)/(n − 1); α = (D₀/D − 1)/(n − 1)

The degree of dissociation is the fraction of molecules split into ions (or fragments) at equilibrium. For weak acids Ostwald’s dilution law shows it rises as the solution is diluted even though Ka is fixed — 0.1 M acetic acid is 1.3% ionised, 0.001 M is 13%. The same α governs colligative properties through the van’t Hoff factor and, for gases that dissociate on heating (PCl₅, N₂O₄), shows up as a vapour density lower than the formula predicts.

Worked example

Acetic acid, Ka = 1.8 × 10⁻⁵, 0.1 M: α = 0.0133 (1.33%), giving [H⁺] = 1.3 × 10⁻³ M and pH 2.88.

Frequently asked questions