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BILLBUILDS
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[*] posted on 17-3-2017 at 20:21
making an acid from a salt


i was wondering how to make an acid from its salt. for example is it possible to get benzoic acid from sodium benzoate. is it possible or is it a one way reactions
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Corrosive Joeseph
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[*] posted on 17-3-2017 at 20:34


"Making Benzoic Acid (from sodium benzoate)"

https://www.youtube.com/watch?v=vGND_cTU4jw


/CJ

[Edited on 18-3-2017 by Corrosive Joeseph]




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[*] posted on 17-3-2017 at 21:37


You are a bit of a mixed bag, BILLBUILDS. On the one hand you are posting on topics or reagents that are borderline drug-related (to the point that it has been suggested at least twice that you are a cook): subjects that involve some pretty high-level understanding of reactions and mechanisms. But now you are asking questions that are basic application of acid-base theory. (And that pun was not intentional but it will do.)



In general, a stronger acid will displace the salt of a weaker acid.


Thus, if X and Y are anions,

HX + NaY --> NaX + HY

where HX is a stronger acid than HY.


(This general principle can fall apart slightly when one or more species is at the limit of its solubility. The formation of a solid removes that species from the system and therefore interrupts the equilibrium relationship. Which means that sometimes conditions can be manipulated to make the reaction work in reverse.)
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[*] posted on 18-3-2017 at 15:41


Quote: Originally posted by j_sum1  
.....

In general, a stronger acid will displace the salt of a weaker acid.

Thus, if X and Y are anions,

HX + NaY --> NaX + HY

where HX is a stronger acid than HY.

(This general principle can fall apart slightly when one or more species is at the limit of its solubility. The formation of a solid removes that species from the system and therefore interrupts the equilibrium relationship. Which means that sometimes conditions can be manipulated to make the reaction work in reverse.)


I also recall reading a similar comment to your last point, where apart from acid strength, there is a factor associated with volatility.

My understanding is that in a reversible reaction, there may be a temperature point, where one acid is, in effect, a gas exiting the system. This could move the equilibrium akin to your reference of a solid. By the way as an example of the latter, once started a thread on making acids from oxalic acid, H2C2O4, which forms many insoluble salts (see https://www.sciencemadness.org/whisper/viewthread.php?tid=18... ).

[Edited on 19-3-2017 by AJKOER]
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[*] posted on 18-3-2017 at 15:57


Yes, both of these effects are due to Le Chatelier's Principle, which generally concludes that if a reactant is present in excess or a product is removed from the system (either by precipitation or off-gassing) the equilibrium of the reaction will shift towards the products, and vice-versa. The principle can also be applied to heat added or removed from the system (think about heat as if it is a reactant or product, depending on whether the reaction is endothermic or exothermic).

https://en.wikipedia.org/wiki/Le_Chatelier's_principle




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[*] posted on 18-3-2017 at 15:58


how would i make formic acid from sodium formate? it seems to be solube in everything. just make it 100% perfect molar ratios? using hcl it should just fall out with nacl right?

[Edited on 19-3-2017 by BILLBUILDS]
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[*] posted on 18-3-2017 at 16:02


That's a tricky one, because if you were making acetic acid from sodium acetate you could simply distill it from sodium acetate with conc. sulfuric acid, but under these conditions, formic acid will readily decompose to water and carbon monoxide. I don't know of any feasible route. When it comes to formic acid, you're better off buying it. It's not that expensive.



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[*] posted on 18-3-2017 at 16:15


Quote: Originally posted by zts16  
That's a tricky one, because if you were making acetic acid from sodium acetate you could simply distill it from sodium acetate with conc. sulfuric acid, but under these conditions, formic acid will readily decompose to water and carbon monoxide. I don't know of any feasible route. When it comes to formic acid, you're better off buying it. It's not that expensive.


Try the oxalic acid route I mentioned above with a link to the thread. The reaction may proceed in the cold, maintaining stability of the formic acid, with the formation of the insoluble sodium oxalate.

[Edited on 19-3-2017 by AJKOER]
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[*] posted on 18-3-2017 at 16:21


Sodium oxalate is much more water soluble than oxalic acid. That idea will not work. No reaction will take place.

If OP had calcium formate it might be possible, but he has sodium formate and converting sodium formate to calcium formate would be as infeasible as converting it to formic acid, so that's a dead end route as well.

[Edited on 3-19-2017 by zts16]




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[*] posted on 18-3-2017 at 16:42


I seem to remember aga posting something about using dilute sulfuric acid to prepare formic acid from sodium formate and crediting the idea to blogfast25. Removing excess water could be tricky, though. I wonder if you could use glacial acetic acid to free the formic acid and fractionally distill.... Of course, it is easier to just buy it.

If you can obtain large quantities of ants, you could distill formic acid out of them.




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[*] posted on 18-3-2017 at 16:49


so far i have found it near impossible to get formic acid and glacial acetic acid and nitric acid. if anyone can recommend australian sources for not to much would be greatful
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[*] posted on 18-3-2017 at 17:01


You need sulfuric acid. In the United States, they sell bottles of it (generally around 90% with inhibitors) at every grocery and department store for pouring down the drain. Other places, it is much hard to obtain....





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