Sciencemadness Discussion Board

Carbonate CO2 absorption

platedish29 - 12-4-2013 at 13:34

Hi, I was wandering trhough the net and as it is always filled with half-scholary texts of sometimes ingenuous people, I've came across this:
(check the link for a page of the experiment the guy has performed)
carbon dioxide absoption by jennifer marohasy
What is the guy just crazy ?
Prolly he'd mistaken gas thermodynamics with chemistry or whatever that seems tricky...



[Edited on 12-4-2013 by platedish29]

Pyro - 12-4-2013 at 13:46

H2O+CO2<->H2CO3
This is why fizzy drinks are fizzy. Though I don't think all that H2CO3 would react with Ca++ ions

plante1999 - 12-4-2013 at 13:51

HA HA HA. Don't believe everything you see. When you burn a candle inside a closed chamber, there is a vaccuum forming, becose you "use" the O2, it is a classical kid demonstration.

H2CO3 is not very stable, more prone to CO2, then to H2CO3

[Edited on 12-4-2013 by plante1999]

platedish29 - 12-4-2013 at 14:44

Ok people frequently tell that slaked lime "readily" absorbs CO2 from the atmosphere. Well... if thats the case, open your big bag of Ca(OH)2 and it is already passed away.. Or is that just the case of CaO?

AndersHoveland - 13-4-2013 at 01:23

Sodium carbonate can slowly absorb CO2 from the atmosphere, so it needs to be stored with an air-tight lid.
Cement lime CaO supposedly can also absorb CO2, but apparently this is very slow and there are typically not any problems with storing it in big paper sacks. It probably absorbs CO2 much faster when wet, and in large clumps most of the lime is protected from reaction.

Fantasma4500 - 13-4-2013 at 05:26

well that Ca(OH)2 does react with CO2 is true, thats why cement or whatever they fill in between bricks hardens.. it turns into CaCO3 (:
its added in concrete/cement, i remember this also because we played around with this in school for building a bridge and everybody was running around washing their hands constantly because it was basic
so they thought they were gonna die, or well close to it

talking about H2CO3, i think its somewhat interesting, as you could plausible use it to produce acids by reacting the acid with a acidsalt, in low concentrations.. but CO2 isnt that hard to get and lead through a solution, the acid could then be isolated relatively easily, problem is if you can react an such weak acid with any salts and well basically if it would even be possible

blogfast25 - 13-4-2013 at 06:13

I suspect that ‘Jennifer’s’ post is another of these crackpot attempts at disproving anthropogenic climate change by means of a test tube experiment, so many of these attempts come wafting over from across the pond.

My favourite one is where they put an ice cube in a glass of water, the ice melts and waddayknow! The water level doesn’t increase! Climate change theory proved wrong in one fell swoop! (Not quite, there's a very simple explanation for this)

Seriously, d*ckheads will be d*ckheads, of course.

CO2 is indeed massively absorbed by the oceans (no one disputes that) but it’s all accounted for in climate change theory.



[Edited on 13-4-2013 by blogfast25]

unionised - 13-4-2013 at 06:25

My word, what a lot of wrongness.
The usual version of the candle in a jar over water looks like it works but the real reason is that the air expands when heated and contracts when it cools again- that's why the water level rises.
There's quite a lot of other nonsense on that page too.

"Sodium carbonate can slowly absorb CO2 from the atmosphere, so it needs to be stored with an air-tight lid. "
no it doesn't. It gains or loses water from the air, but that's another matter.

"Ok people frequently tell that slaked lime "readily" absorbs CO2 from the atmosphere. Well... if thats the case, open your big bag of Ca(OH)2 and it is already passed away."
Ca(OH)2 does pick up CO2 from the air, but, of course, the stuff at the bottom of the bag isn't exposed to the air (and almost all the air isn't CO2). So, overall, the reaction is quite slow.

There are a number of things used to cement bricks together. the simplest of them is a mixture of calcium hydroxide , sand and water. This does harden by reaction with CO2 but the reaction is so slow that even the stuff that the Romans used hasn't finished setting yet (the surface has set and the stuff in he middle has dried out so it's all solid)
Most of the cement currently used is more like Portland cement, it's a mixture of calcium silicates and the setting process is more complicated. It doesn't involve CO2 from the air.
However the stuff is still strongly alkaline and it's a good idea to wash it off your hands.

Antiswat's point is valid, within limits. For example CO2 was used as a cheap acid to displace phenol from solutions of sodium phenoxide in the days when phenols were made from coal tar.
But this only works because phenol is a very weak acid.
You can't use CO2 to make any acid stronger than carbonic acid and that's a very weak acid.

mayko - 13-4-2013 at 13:37

Argle. Ocean acidification denial is rarer than its global warming cousin, but it's no prettier.
Quote:

“THE oceans take out our anthropogenic carbon dioxide gas by quickly dissolving it as bicarbonate HCO3-, which in turn forms solid calcium carbonate


When CO2 dissolves, it forms carbonic acid, H2CO3. This dissociates to H+ and HCO3-; the H+ subsequently reacts with CO3(2-) to form HCO3-, for a net reaction of
CO2 + H2O + CO3(2-) -> 2 HCO3-

tl;dr, adding CO2 to the ocean does not precipitate carbonate. It converts existing carbonate into bicarbonate, thus lowering the saturation state of CaCO3. And that's bad news for calcifiers like corals, which provide irreplacable ecosystem services for millions.

Furthermore, dumping calcium hydroxide into the bowl is cheating; the geochemical analogy would be a sudden massive influx of alkalinity to the oceans. The increasing Ca2+ can make up for the decreasing [CO3(2-)], maintaining or even increasing the saturation state of the carbonate. On long time scales this can actually happen, since increased CO2 accelerates weathering of rocks, and hence increases the flow of alkalinity to the oceans. This is why the high-CO2 cretaceous is marked by chalk deposits like the White cliffs of Dover, and why snowball earth terminations are marked by carbonate caps. However, on human timescales, the alkalinity of the oceans will be more or less constant, and the saturation state of CaCO3 will drop.





blogfast25 - 14-4-2013 at 05:20

Having read through some of the comments on ‘Jennifer’s’ blogpost, what stands out is what always stands out on laymen’s sceptic’s blogs: atrocious spelling!

Then ‘Jennifer’ herself wades in, not wanting to be found lacking in sceptics credentials:

”PS – I am not a warmist. I have no doubt that CO2 is not responsible for any measurable warming of the planet, nor is it anywhere near close to toxic concentrations for fauna, or anything else for that matter, but is in fact beneficial to plants (and so food production) at the very least. My only concern here is that the video demonstration is sloppy, and doesn’t show what it claims to show, for the reasons I’ve given.”

All of it gives a measure of the level or argumentation used in sceptics circles…

AJKOER - 14-4-2013 at 14:10

To quote: "You can't use CO2 to make any acid stronger than carbonic acid and that's a very weak acid."

This is true if you are not much of a chemist. For example, one could add NaOCl and form an even weaker acid like HOCl:

H2CO3 + NaOCl --> NaHCO3 + HOCl

Next, distill half the solution to capture a large majority of the HOCl and leave the carbonate behind. Follow up with sunlight (or the presence of certain metals,..), as Hypochlorous acid decomposes as follows:

HOCl --> HCl + O2 (g)

and a small amount may even disproportionate as follows in diffused light:

3 HOCl --> 2 HCl + HClO3

Now, this is still dilute HCl, but there are ways of concentrating, with some qualifications, even dilute HCl (see my answer on a recent thread).


[Edited on 14-4-2013 by AJKOER]

plante1999 - 14-4-2013 at 14:16

Argggggggggggggggg!

I'm tired of your hypochlorite pathway. I mean, can you please start to do some real chemistry with real glassware? At least stop to talk about hypochlorites!

AJKOER - 14-4-2013 at 14:26

Plantee1999:

In my opinion, some organic hypochlorites are just too dangerous even to talk about in a general audience (and I certainly wouldn't be using any form of glassware with these hypochlorites, expensive or not).

I did a thread once on the suggested use of Copper hypochlorite as a path to KClO3 (an actual old commercial process).

[Edited on 14-4-2013 by AJKOER]

platedish29 - 16-4-2013 at 10:58

For the CO2 absorption in water, once my history teacher told me her son dealed with a carbon dioxide generator for aquariums which turned out his aquatic plants to overgrow into man-eating fauna! lol
And as for Ca(OH)2 absorption, I did an experiment with my 5-year old plastic bag of lime and it has tricked me many times as some "fezzilings" were took as just heat of enthalpy from reactions with acids, but in fact it was releasing CO2 by what I would put the carbonate content at aprox. 20% - 50% of the total mass of the stored sample.
It can stillbe dissolved in water to make it basic, as showed the lime water I prepared for washing exposed elemental iron.

Thats more on the concept of hardness and softness rather than strnght of an acid IMO. Where did your good chemical intuition go fellas? Have you fallen with the approach of afinity to incline for blackboard equations?
Come on how may one approach a relation between softeness hardness as simply predicted by the acid strenght??? Have you gone mad?!

lol



[Edited on 16-4-2013 by platedish29]

mayko - 16-4-2013 at 13:06

Quote:
For the CO2 absorption in water, once my history teacher told me her son dealed with a carbon dioxide generator for aquariums which turned out his aquatic plants to overgrow into man-eating fauna! lol


Much of the ocean is limited by iron, not CO2. ( Nature 383, 508 - 511 (10 October 1996); doi:10.1038/383508a0 ) Moreover, as the oceans warm they stratify, and iron limitation spreads.

Hoping that CO2 fertilization will solve our problems for us is wishful thinking.


Quote:

Thats more on the concept of hardness and softness rather than strnght of an acid. Where did your good chemical intuition go fellas? Have you fallen with the approach of afinity to incline for blackboard equations?
Can you proff a relation between softeness hardness as simply predicted by an acid strenght???


I'm not sure, but it sounds like you're talking about alkalinity and its role in the ocean carbon system:
Quote:

There are 4 measurable parameters of the carbonic acid
system in seawater: pH, dissolved inorganic carbon (DIC), total alkalinity (TA), and CO2 partial pressure (pCO2). [...]
Measurements of seawater pH are less often obtained than
those of DIC, TA, or pCO2oce despite the facility and precision of the colorimetric analytical method

( PNAS ͉ July 28, 2009 ͉ vol. 106 ͉ no. 30 ͉ 12235–12240 )

It wasn't until I started reading up on ocean chemistry that I learned that alkalinity and basicity are not the same. It turns out that it's at the heart of a technique for measuring calcification rates in shelled organisms, which I found to be quite clever:
Quote:

Net calcification rates (G in mmol CaCO3 g FW^-1 h^-1 ) were estimated using the alkalinity anomaly technique
[Smith and Key, 1975] following the equation:
G = DTA/2
Where DTA is the variation of TA during the incubations in
meq g FW^-1 h^-1. This technique is based on the fact that the precipitation of 1 mole of CaCO3 consumes 2 moles of
HCO3-, therefore decreasing TA by 2 equivalents


(GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L07603)