Actually as long as we are close enough to pKa2 (say any pH between 5 and 9) we don't have to worry - both other dissociations steps are far enough to not matter. In the end I would use Buffer Maker Logged Chembuddychemical calculators - stoichiometry, pH, concentration, buffer prepar...
The PFF pKa values for cysteine are within about 0.8–2.8 pH units of the experimental data, while the fixed-charges OPLS formalism yields errors of up to tens of units. The PFF magnitude of the copper binding energy is about 10 kcal/mol or 50% higher than the experimental value, while...
where pKa is the negative of the logarithm of the ionization constant of the weak acid (pKa = −log Ka). This equation relates the pH, the ionization constant of a weak acid, and the concentrations of the weak conjugate acid-base pair in a buffered solution. Scientists often use this ...
Re: Calculating exact pH of a buffer « Reply #3 on: January 24, 2013, 04:00:59 AM » Where did you got pKa of 6.82 from? Correct value (not corrected for ionic strength) is 7.2. Logged Chembuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titratio...