Convert between Ka and pKa and find the pH of half-dissociation.
At pH equal to pK_a an acid is exactly half ionised, which is why pK_a is read directly off a titration curve at half equivalence. Two units either side of pK_a corresponds to about 99 per cent in one form. The ionisation state at physiological pH governs drug absorption and distribution, which is why pK_a is central to pharmacology.
pKa
pK_a = −log₁₀K_a; ionised fraction = 10^(pH−pK_a) ÷ (1 + 10^(pH−pK_a))
pK_a = −log₁₀K_a; ionised fraction = 10^(pH−pK_a) ÷ (1 + 10^(pH−pK_a)) At pH equal to pK_a an acid is exactly half ionised, which is why pK_a is read directly off a titration curve at half equivalence. Two units either side of pK_a corresponds to about 99 per cent in one form.
The ionisation state at physiological pH governs drug absorption and distribution, which is why pK_a is central to pharmacology.
This calculator takes 2 inputs: Acid dissociation constant, Solution pH. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.