The Henderson-Hasselbalch Equation
An equation that relates pH, pKa and the ratio of
weak acid to its conjugate base for a buffer solution.
HA + H2O H3O+ + A-
Ka = [H3O+][A-]/[HA]
[H3O+] = Ka x [HA]/[A-]
-log [H3O+] = -log Ka - log ([HA]/[A-])
pH = pKa + log ([A-]/[HA])
pH = pKa + log ([base]/[acid])
Special case: when [base] = [acid], the pH of the buffer
solution equals the pKa of the weak acid.
or
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