Dissociation degree of polyprotic acids

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The discussion centers on the application of the Henderson-Hasselbalch equation to calculate the dissociation degree of monoprotic acids and its potential use for polyprotic acids. The formula derived from the equation allows for the calculation of the ratio of the concentrations of the acid and its conjugate base using pH and pKa values. Participants confirm that this method is valid for polyprotic acids as well, emphasizing that the equation is a rearrangement of the dissociation constant definition. Additionally, the formula is highlighted as useful in analyzing endpoint detection accuracy in acid/base titrations, where similar calculations are applied.
ComptonFett
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I can quickly calculate the dissociation degree of a monoprotic acid with the formula below (derived from the Hendersson-Hasselbach equation). I don't see any reason why this would not work also for polyprotic acids but I would like to confirm that it does. I would appreciate it if someone could confirm/disconfirm this. Thanks.

\begin{align}
& pH=pKa+\log \frac{A^{-}}{HA} \\
& \log \frac{A^{-}}{HA}=pH-pKa \\
& \frac{A^{-}}{HA}=10^{pH-pKa} \\
\end{align}
 
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Yes it will work - pH and pKa are enough to calculate ratio of acid and conjugate base concentrations.

As Henderson-Hasselbalch equation is just a rearranged form of the dissociation constant definition, formula you derived is also just a rearranged form of the dissociation constant definition. It is quite useful in the analysis of the endpoint detection accuracy (see discussion of acid/base titration indicators where the same formula is used).
 
Cheers!
 
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