Ostwald dilution law (weak electrolyte) (Ka = C α²/(1−α); if α << 1, Ka ≈ C α²)

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Ka = C α²/(1−α); if α << 1, Ka ≈ C α²

What each symbol means

SymbolWhat it stands for
CInitial concentration of weak electrolyte (mol L⁻¹)
αDegree of dissociation / ionisation
K_aIonisation constant

When to use this

Single-step weak acid/base in water; dilute solution; for α small, √(Ka/C) works.