Dissociation degree of polyprotic acids

In summary, the formula derived from the Henderson-Hasselbach equation can be used to calculate the dissociation degree of both monoprotic and polyprotic acids. This formula is a rearranged form of the dissociation constant definition and is useful for analyzing endpoint detection accuracy in acid/base titrations.
  • #1
ComptonFett
8
0
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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  • #2
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).
 
  • #3
Cheers!
 

1. What is the dissociation degree of a polyprotic acid?

The dissociation degree of a polyprotic acid is the measure of the extent to which the acid dissociates in a solution. It is expressed as a percentage, with 100% representing complete dissociation and 0% representing no dissociation.

2. What factors affect the dissociation degree of polyprotic acids?

The dissociation degree of polyprotic acids can be affected by factors such as the strength of the acid, the concentration of the acid, the presence of other ions in the solution, and temperature.

3. How is the dissociation degree of polyprotic acids calculated?

The dissociation degree of polyprotic acids can be calculated using the Henderson-Hasselbalch equation, which takes into account the acid dissociation constant (Ka) and the concentrations of the acid and its conjugate base in the solution.

4. What is the significance of the dissociation degree of polyprotic acids?

The dissociation degree of polyprotic acids is important in determining the strength of the acid and its ability to donate protons in a solution. It also affects the pH of the solution and can impact the reactivity of the acid in certain chemical reactions.

5. Can the dissociation degree of polyprotic acids change?

Yes, the dissociation degree of polyprotic acids can change depending on the conditions of the solution. For example, increasing the concentration of the acid or decreasing the pH can lead to a higher dissociation degree, while the presence of other ions can decrease the dissociation degree.

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