tag:blogger.com,1999:blog-7729093380675162051.post2927673549494859021..comments2024-03-28T13:56:47.604+11:00Comments on moyhu: Buffers and ocean acidification.Nick Stokeshttp://www.blogger.com/profile/06377413236983002873noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-7729093380675162051.post-6113544512457162112018-04-19T09:31:18.683+10:002018-04-19T09:31:18.683+10:00Eli,
"While using the Lewis acid/base idea is...Eli,<br /><i>"While using the Lewis acid/base idea is a bridge too far"</i><br />Well, as I said of it:<br /><i>"I've realised now that that isn't necessary, because the notion of buffering isn't tied to any notion of acidity."</i><br />Lewis acidity has been around longer than Bush the Elder, and I think it is useful for explaining reactions in the absence of protons, eg<br />CaO+CO₂→ CaCO₃ <br />And it's also useful if protons are sparse, because they aren't really a reagent (just an intermediate) unless pH is low. But the main thesis here is that you don't need any notion of acidity to explain buffering. It's just law of mass action.<br />Nick Stokeshttps://www.blogger.com/profile/06377413236983002873noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-92028819887938192782018-04-19T08:58:29.108+10:002018-04-19T08:58:29.108+10:00While using the Lewis acid/base idea is a bridge t...While using the Lewis acid/base idea is a bridge too far, Arrhenius is too little.<br /><br />Bronsted Lowry is just right. An acid is a proton (hydrogen ion) donor, and a base is a hydrogen ion acceptor. <br /><br />Seawater, of course has a whole lot of polyatomic ions of salts which act as basesEliRabetthttps://www.blogger.com/profile/07957002964638398767noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-19942766408739343992018-04-18T08:39:08.320+10:002018-04-18T08:39:08.320+10:00Peter,
"Interesting comment about taking a lo...Peter,<br /><i>"Interesting comment about taking a long time to equilibrate when experimentally..."</i><br />What I said was:<br /><i>"Of course that is an equilibrium calculation, and the mixing time of the whole ocean is very long, so it could only apply to surface layers."</i><br />The reactions themselves are fast. The issue is diffusion/transport, and the length scales involved. As long as there is a concentration gradient involved, the reaction is not at equilibrium. Here the driver is increased CO2 at the surface. The effect takes time to propagate downward.<br />Nick Stokeshttps://www.blogger.com/profile/06377413236983002873noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-30298284774234261892018-04-18T03:16:36.293+10:002018-04-18T03:16:36.293+10:00OK analogy apart from the slow diffusion to seques...OK analogy apart from the slow diffusion to sequestering sites.@whuthttps://www.blogger.com/profile/18297101284358849575noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-50507819366097066522018-04-17T23:58:17.057+10:002018-04-17T23:58:17.057+10:00Interesting comment about taking a long time to eq...Interesting comment about taking a long time to equilibrate when experimentally it has been found that CO2 and pure water at 25 degrees C reaches 99% isotopic equilibrium after 30 hours and 52 minutes; after shaking (like wave agitation) 99% equilibrium is reached after 4 hours and 37 minutes (Gonfiantini, 1981). At 350ppmv CO2 in the air, the equilibrium concentration of carbonic acid in pure water will be about 0.00001 molal at 25 degrees C. This chemical equilibrium is reached within 20seconds (Stumm & Morgan, 1970). At the same temperature, at pH-values between 7 and9, CO2 reaches 99% chemical equilibrium with water and calcium carbonate in about 100seconds (Dreybrodt et al., 1996).<br />Carbonated beer, soda "pop", and champagne are good analogues to the CO2<br />distribution between atmosphere and ocean. In both cases they manifest the equilibrium<br />governed by Henry's Law: the partial pressure of CO2 in the air will be proportional to the<br />concentration of CO2 dissolved in water. The proportional constant is the Henry's Law<br />Constant, giving us a partition coefficient for CO2 between air and water of approximately<br />1:50 (Revelle & Suess, 1957; Skirrow, 1975; Jaworowski et al., 1992 a; Segalstad, 1996).<br />Machahttps://www.blogger.com/profile/07923852608052498080noreply@blogger.com