Talk:Carbonic acid/Archives/2022

pK value: repeated reversion

This is a very troublesome issue. The origin of the error is explained in note 1, of the article text, reproduced here for convenience.

Note 1: There are apparently conflicting values in the literature for pK_a. Pines et al. cite a value for "pK_a,app" of 6.35 for $K_{a,{\text{app}}}={\frac {[{\text{H}}_{3}{\text{O}}^{+}][{\text{HCO}}_{3}^{-}]}{[{\text{CO}}_{2}]}}$, consistent with the value 6.77, mentioned above.

In the Pines paper they also give a value for "pK_a" of 3.49 and state that

pK_a = pK_app − log K_D (eqn. 5)

where K_D=[CO₂]/[H₂CO₃]. (eqn. 3)

The issue in this Wikipedia article arises from the way that the dissociation constants are named and defined in the Pines paper which is clearly stated in the text of the paper, but not in the abstract, leading to the possibility of misinformation when relying only on its abstract. Petergans (talk) 15:45, 3 May 2022 (UTC)