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)

What?

This is not accessible to a lay reader. Azbookmobile (talk) 16:55, 5 September 2022 (UTC)

So what do you propose for a solution? Also, if you look a a technical article in Encyclopedia Britannica you will find the same "problem". When I was a kid we had a neighbor who had a set of Britannicas. I was fascinated by them - stuff I did not understand challenged me to dig deeper and learn. When I graduated high school and got a job, my first purchase was a set of Britannicas -- and I learned. Vsmith (talk) 18:07, 5 September 2022 (UTC)

Pressure dependence?

Random thought: is it more stable at pressure in the deep ocean? The reaction H₂CO₃ ⇌ CO₂ + H₂O would sort of imply that it would be, assuming dissolved CO2 got down that far. Project Osprey (talk) 10:03, 6 September 2022 (UTC)

No expert here, but one has to assume that dissolved CO₂ "gets that far" for sure, but I dont think that its partial pressure is greater at depth than at the surface. With all the interest in ocean acidification, smart people somewhere must be thinking of this aspect. --Smokefoot (talk) 14:58, 6 September 2022 (UTC)

The article doesn't give a equilibrium constant for dissolved CO₂ ⇌ carbonic acid, but there must be one. Le Chatelier's principle would surely mean more carbonic acid at depth, but would that mean the ocean would be more acidic at depth? With the acidity just fizzing back out as you went up? It sounds reasonable but also weird. I don't think I'm right. --Project Osprey (talk) 15:53, 6 September 2022 (UTC)