Sciencemadness Discussion Board

Acetic Acid and Sodium Chloride

Eddygp - 17-3-2013 at 04:00

It turns out that mixing 8% acetic acid with common salt does generate a significant amount of hydrochloric acid: I moved a beaker containing an ammonia solution to it and the ammonium chloride vapour/crystals formed rapidly!
Just surprised at this...

Adas - 17-3-2013 at 09:30

It was probably just ammonium acetate, HCl was not formed.

Eddygp - 17-3-2013 at 12:09

Does ammonium acetate form in the gas phase?

Endimion17 - 17-3-2013 at 12:59

Quote: Originally posted by Eddygp  
Does ammonium acetate form in the gas phase?


If you're implying that ammonium chloride smoke from the classical reaction is in gas phase, you're wrong. It's an aerosol. Solid particles = smoke.

I don't remember I saw such smoke with ammonia and acetic acid fumes. It might be because it's too hygroscopic... Just a guess.

DraconicAcid - 17-3-2013 at 13:01

Quote: Originally posted by Endimion17  
Quote: Originally posted by Eddygp  
Does ammonium acetate form in the gas phase?


If you're implying that ammonium chloride smoke from the classical reaction is in gas phase, you're wrong. It's an aerosol. Solid particles = smoke.

It's not *in* the gas phase, but it *forms in* the gas phase (from gaseous reactants).

Eddygp - 18-3-2013 at 01:51

I meant what DraconicAcid said, that it forms from gaseous reactants. So I saw the classic white ammonium chloride forming in the air.

SM2 - 18-3-2013 at 06:12

AA never gets quite dry. As far as forming aq HCL from weenigar and salz, to me it doesn't seem theoretically possible. But I'm not nearly as smart as many are here, so consider it a guess. However; you can clean old pennies using a little vinegar and table salt. Is it the scrubbing action of the salt along with acetic acid. Are we to assume on most old pennies, the dirty film consists of various amounts of whatever, including copper carbonate, and then the acetic acid alone would work. More experiments to be done. Haven't taken a pH meter to it, but my nose did seem to smell HCL from the mixture of salt and white vinegar, where the salt was in much greater proportion to the vinegar. just wet a small pile of table salt with maybe 10 drops of white vinegar.

Eddygp - 18-3-2013 at 06:38

Yes, I decided to test it because of the smell. If it has formed, it won't be in large quantities, logically, but it has been enough for me to be able to detect it with ammonia (NH3+HCl=NH4Cl), giving a positive result. Moreover, I had covered the glass with a metal tap (the one of a jam jar), and it seems to have rusted at the edges... Very interesting.

Adas - 18-3-2013 at 07:48

Quote: Originally posted by Eddygp  
Yes, I decided to test it because of the smell. If it has formed, it won't be in large quantities, logically, but it has been enough for me to be able to detect it with ammonia (NH3+HCl=NH4Cl), giving a positive result. Moreover, I had covered the glass with a metal tap (the one of a jam jar), and it seems to have rusted at the edges... Very interesting.


Chloride ions may act as catalysts, e.g. when you clean pennies with vinegar + NaCl, and solutions of NaCl are capable of slowly dissolving Al foil.

Eddygp - 18-3-2013 at 11:56

I know, but what I'm trying to say is that some HCl formed, because the reaction I stated only occurs with gaseous HCl and NH3 from an adjacent beaker, also in gas form.

franklyn - 18-3-2013 at 13:00

So that's why people are dropping dead in restaurants ,
it's the vinaigrette on their salads.

.

bahamuth - 18-3-2013 at 13:59

IIRC hydrochloric acid is formed in situ in some reactions by the action of acetic acid upon sodium chloride, though I do not remember where or what.

I doubt that the hydrochloric acid formed reaches any appreciable amount, much less enough to escape the mix as gas and form ammonium chloride with ammonia. My guess it that you have seen ammonium acetate forming, as this reaction is visually analogous to NH4Cl formation.

Only reference I bothered find for this is from the University of Minnesota.
http://www.chem.umn.edu/outreach/card-saltvincopper.html

Eddygp - 18-3-2013 at 14:08

It would probably be ammonium acetate, but I did notice a stench similar to that of hydrochloric acid, apart of the "vinegary" smell.

AJKOER - 22-3-2013 at 08:40

Quote: Originally posted by bahamuth  
IIRC hydrochloric acid is formed in situ in some reactions by the action of acetic acid upon sodium chloride, though I do not remember where or what.

I doubt that the hydrochloric acid formed reaches any appreciable amount, much less enough to escape the mix as gas and form ammonium chloride with ammonia. My guess it that you have seen ammonium acetate forming, as this reaction is visually analogous to NH4Cl formation.

Only reference I bothered find for this is from the University of Minnesota.
http://www.chem.umn.edu/outreach/card-saltvincopper.html


Hydrometallurgy frequently employs weak acids (citric, tartaric,..) in highly ionic salt solutions to dissolve ores. This is simply a matter of economics, and more recently, green economics (more environmentally friendly ore processing).

My understanding is that in water stressed conditions (from high concentrations of NaCl, MgCl2, FeCl3,..) the strength (or 'activity level') of even otherwise weak acids (or very dilute strong acids) is significantly increased.

This may be at play here, hence the reference source (http://www.chem.umn.edu/outreach/card-saltvincopper.html ) comment, to quote:

"Explanation:
Salt, or sodium chloride, combines with acetic acid from the vinegar to produce sodium acetate and hydrogen chloride. Hydrogen chloride is a strong acid and the combination of it and sodium acetate rapidly cleans the surface of the penny"

But the explanation is not correct, IMHO, as it is stilled the stronger acetic acid, not the HCl, accounting for the reaction on the surface of the penny.

[Edited on 22-3-2013 by AJKOER]

DraconicAcid - 22-3-2013 at 09:04

Quote: Originally posted by AJKOER  
Hydrometallurgy frequently employs weak acids (citric, tartaric,..) in highly ionic salt solutions to dissolve ores. This is simply a matter of economics, and more recently, green economics (more environmentally friendly ore processing).

My understanding is that in water stressed conditions (from high concentrations of NaCl, MgCl2, FeCl3,..) the strength (or 'activity level') of even otherwise weak acids (or very dilute strong acids) is significantly increased.

Citrate and tartrate will form complex ions with transition metals, rendering the metals more soluble, and increasing their acidity. Sodium chloride, on the other hand, may have an effect simply by increasing the ionic strength of the solution.
Quote:
This may be at play here, hence the reference source (http://www.chem.umn.edu/outreach/card-saltvincopper.html ) comment, to quote:

"Explanation:
Salt, or sodium chloride, combines with acetic acid from the vinegar to produce sodium acetate and hydrogen chloride. Hydrogen chloride is a strong acid and the combination of it and sodium acetate rapidly cleans the surface of the penny"

But the explanation is not correct, IMHO, as it is stilled the stronger acetic acid, not the HCl, accounting for the reaction on the surface of the penny.


I think the only thing the salt does in the "penny-cleaning" reaction is to provide chloride ion to complex with the copper ions. I could be wrong.

[Edited on 22-3-2013 by DraconicAcid]

AJKOER - 22-3-2013 at 12:32

On re-thinking, my same argument (increased acid strength for a weak acid in a water stressed high ionic environment) means that adding a few drops of hot vinegar to a pile of salt may be able to form a small amount of gaseous HCl (which may be tested with ammonia fumes). Alternately, one could argue that the concentrated brine solution just makes the Acetic acid more volatile and easier to distill (an observation employed successfully in concentrating acids).

However, IMHO no net HCl will be formed in a closed system as I suspect the reverse reaction occurs (HCl gas in contact with moist Sodium Acetate forms NaCl and Acetic acid). In other words, the odor of HCl may be fleeting in a closed container.

One could assume, at best, a reaction parallel to the action of HOCl on NaCl:

NaCl + HOCl <--> NaOH + Cl2

where the smell of Cl2 is at first evident, but the equilibrium is re-established and the chlorine smell dissipates (see http://books.google.com/books?id=9WY6AAAAMAAJ&pg=PA227&a... ).


[Edited on 23-3-2013 by AJKOER]

KonkreteRocketry - 22-3-2013 at 12:57

How much concentration of HCl can i get, if i do this...

NaCl + 7% Acetic acid, then wait for few min for reaction, then put the bottle inside a -5 degree fridge to freeze the water and then pour the rest of the liquid out..

AJKOER - 22-3-2013 at 13:30

Quote: Originally posted by KonkreteRocketry  
How much concentration of HCl can i get, if i do this...

NaCl + 7% Acetic acid, then wait for few min for reaction, then put the bottle inside a -5 degree fridge to freeze the water and then pour the rest of the liquid out..


There are much much better paths to dilute HCl, but my initial thoughts on performing this particular experiment would be to add drops of vinegar to a pile of NaCl sitting in a dish surrounded by a small amount of distilled water, all of which is in a closed container and partially crushed to allow for expansion. Briefly heat the vessel in a microwave. The logic (speculation) is that any formed HCl gas is absorbed in the water and not returned to the system (at least, not in the short run). Wait until all the fumes are gone, stir and/or replenish the pile of salt, and add more vinegar....
-----------------

Another embodiment would be to place some distilled water (or ice) in a balloon connected to a bottle placed horizontally containing an excess of salt to vinegar. Heat in a microwave until max expansion of the balloon containing water. Remove and cool the balloon and recover the product.

In all embodiments, I expect the distilled water to contain some HCl (or none) and vinegar (from the heating and condensation).

[EDIT] I performed several experiments. First, I heated a small amount of vinegar in a partially crushed bottle (to allow for expansion) in a microwave. To this upon opening, I added increments of salt, smelling after each addition. Interestingly, the smell of vinegar was sharply cut with the addition of large amount of NaCl. I then reheated the excess salt/vinegar in a partially crushed bottle to expansion (plus a few seconds) and then ran cold water over the top half of the bottle. I witnessed a surprising complete crushing of the bottle.

I repeated with plain water and also using plan vinegar, but in neither case was there such a magnitude of crushing. I also noticed that the bottle reaches max expansion faster with the excess salt/vinegar mixture.

I repeated the experiment of heating an excess of salt with vinegar in a partially crushed bottle to expansion (plus a few seconds). This time, the bottle cap popped off with a loud noise. I replaced the cap and ran cold water over the top half of the bottle. I witnessed a surprising crushing of the bottle to about the original preheating size (remember, this was from a previously opened bottle).

Conclusions: The rapid expansion and contraction witnessed are in line with a gas (like HCl or a volatile acetic acid escaping from the brine solution) formation that is highly soluble in water (which I was not able to distinguish, however, from the sharp smell of vinegar). I can only explain the magnitude of crushing by assuming that the Hydrogen chloride (or Acetic acid vapors) formed pushed out some of the air, that is, the bottled cap leaked under pressure, leaving largely gaseous HCl (or Acetic acid) and very hot water.

Also, the drops of vinegar to dry NaCl mixture should be heated for best results.

Note, on net no aqueous HCl was produced in this experiment as any formed would have reacted with the Sodium acetate. Also, no definite proof it was, in fact, just HCl gas.

[EDIT][EDIT] I repeat again the experiment twice with a NaCl/Acetic acid mix and once with just Acetic acid. On heating in a microwave, again the NaCl/Acetic acid mix bottle re-inflated the fastest. This time I held an ammonia solution to the neck of each bottle. In both cases, no NH4Cl smoke ring visible. I then added a little aqueous ammonia to the bottle and push in, and I did witness repeatedly the formation of light smoke rings (similar to what a tobacco smoker forms) with the NaCl/Acetic acid mix, but not with the pure Acetic acid bottle. As I observed, the rings were not as intensely white as I have seen in the presence of chlorine, but still evident.

Revised Conclusion: Barring explanations to the contrary, one might conclude that a small amount of very dilute HCl was indeed produced. Most likely, however, not a practical source of dilute HCl, but some may find the results theoretically interesting (and those who dismiss my conclusions are welcomed to repeat this simple experiment for themselves).

[Edited on 23-3-2013 by AJKOER]

[Edited on 23-3-2013 by AJKOER]

AJKOER - 23-3-2013 at 13:55

It is still possible, however, that a small amount of condensed more concentrated acetic acid did react with the ammonia producing a white Ammonium acetate salt, which could be responsible for the mild smoke rings, that I observed (I have not, as of yet, found any reports confirming this speculation on the gaseous formation of Ammonium acetate). [EDIT] To quote this source (http://chestofbooks.com/food/beverages/A-Treatise-On-Beverag... ):

"3. Ammonia may be detected also by slightly acidifying the water with muriatic acid, evaporating to dryness and adding to residue some caustic potash or soda solution. On holding the glass rod, previously dipped in acetic acid or diluted nitric acid, in close proximity to the residue, a thick white fog will be visible. (Hager.)"

So acetic acid (of sufficient strength I would guess) and ammonia can produce a "white fog", which is apparently the white Ammonium acetate salt.

So the formation of any HCl (from heating a large excess of dry NaCl with vinegar) is apparently still not definite, IMHO.


[Edited on 23-3-2013 by AJKOER]

KonkreteRocketry - 24-3-2013 at 04:21

So is HCl produced actually in this reaction ? I asked my chem teacher who say it dosent happen ?

Eddygp - 24-3-2013 at 04:58

NaCl would dissociate more strongly in acetic acid solution than in distilled water, and the protons H+ that the acetic acid would give out could, in a very small quantity, react with the chloride anions to create HCl, but I'm not sure if this could react noticeably (HCl would easily react with sodium acetate to yield sodium chloride and acetic acid).

DutchChemistryBox - 24-3-2013 at 06:15

Maybe i'm stupid, but HCl is a strong acid.
So it has a Ka greater than 1.

So the conjugated base (which is Cl-) must have a Kb which is smaller than 10^-14.


I can't understand why the H+ wil stick to the Cl- when it has such a small Kb.

If you ask me, it isn't possible to create HCl with just acetic acid and NaCl

Correct me if I'm wrong

*i hope my englisch is readable*

woelen - 24-3-2013 at 06:52

If you add NaCl to acetic acid, then there will be an equilibrium reaction, but this reaction will be very strongly to the side of NaCl + CH3COOH.

CH3COOH + NaCl <<<<----> CH3COONa + HCl

In practice I think that the amount of HCl will hardly be observable, it will at best be formed in trace amounts.

This reaction with somewhat weak acids can be used to make HCl, if there is another driving force, which takes away the HCl from the system. An example is heating of a mix of NaHSO4 + NaCl. NaHSO4 is a moderately weak acid, but it is stronger than acetic acid. If you heat a mix of NaHSO4 and NaCl, then there is an equilibrium with Na2SO4 and HCl. Again, this equlibrium is quite strongly to the side of NaHSO4 and NaCl, but in the hot (e.g. around 100 C) mix, the HCl is the only gas and then this gas can escape and in this way, the reaction is driven to the side of Na2SO4 and HCl. This reaction is not a really practical method of making HCl, but enough HCl can be made in this way such that it is clearly visible (fuming).

KonkreteRocketry - 25-3-2013 at 08:39

Quote: Originally posted by woelen  
If you add NaCl to acetic acid, then there will be an equilibrium reaction, but this reaction will be very strongly to the side of NaCl + CH3COOH.

CH3COOH + NaCl <<<<----> CH3COONa + HCl

In practice I think that the amount of HCl will hardly be observable, it will at best be formed in trace amounts.

This reaction with somewhat weak acids can be used to make HCl, if there is another driving force, which takes away the HCl from the system. An example is heating of a mix of NaHSO4 + NaCl. NaHSO4 is a moderately weak acid, but it is stronger than acetic acid. If you heat a mix of NaHSO4 and NaCl, then there is an equilibrium with Na2SO4 and HCl. Again, this equlibrium is quite strongly to the side of NaHSO4 and NaCl, but in the hot (e.g. around 100 C) mix, the HCl is the only gas and then this gas can escape and in this way, the reaction is driven to the side of Na2SO4 and HCl. This reaction is not a really practical method of making HCl, but enough HCl can be made in this way such that it is clearly visible (fuming).


Can i pour Acetic acid onto a hot salt plat ? it will touch the salt and like vapourize in seconds making the HCl escape before it goes back to NaCl ?

can i simply add salt + acetic acid and boil it for HCl to come out ? because it has a much lower boiling point and so much more likely to escape than the acetic acid ? seems like a good idea ?

Than i can connect the whole thing to a tube and put the HCl gas into a water solution and ill get a HCl solution right ?

woelen - 25-3-2013 at 10:34

No, that will not work. Acetic acid and HCl are so far away in strength that the equilibrium is nearly 100% (i.e. 99.999...%) at the side of NaCl and CH3COOH. If you pour CH3COOH on solid hot NaCl, then you just get a lot of acetic acid vapor and no HCl.

If you can't get HCl, then try to find so-called pH-minus (which is NaHSO4.H2O) and mix that with NaCl and heat this mix. The hydrated NaHSO4.H2O melts in its own water of crystallization at 60 C or so and then it dissolves NaCl and on further heating, HCl will leave the mix fairly easily, together with water vapor.

Nicodem - 25-3-2013 at 12:27

Quote: Originally posted by Eddygp  
Yes, I decided to test it because of the smell. If it has formed, it won't be in large quantities, logically, but it has been enough for me to be able to detect it with ammonia (NH3+HCl=NH4Cl), giving a positive result. Moreover, I had covered the glass with a metal tap (the one of a jam jar), and it seems to have rusted at the edges... Very interesting.

How very unscientific. You can't call a result positive unless you test also for a negative result of the control experiment. So, instead of performing also a control experiment, you jumped to conclusions without any evidence whatsoever. Indications are not evidence, they do just what the word means: indicate. An indication can never become evidence unless coupled with at least one opposite indication. Please, learn the basics of the scientific method.

jimmyboy - 7-2-2016 at 16:39

this is Necromancy for this old thread but I was asked this question recently about how pennies get cleaned faster combining vinegar and salt
.. maybe the NaCl is just a catalyst but I think the problem is the dissociation constant of HCl

.. HCl, HBr, HI, HNO3, HClO3, HClO4 are the strong acids and always completely dissociate in solution .. so forming a strong acid with a weak one is next to impossible in solution since the dissociation is irreversible
.. hydronium and chloride ions will not reunite inside the water solution to form HCl acid under normal conditions .. so you will not get Hydrochloric
.. to prove it you just need distillation and use the boiling points of HCl and Acetic

blogfast25 - 7-2-2016 at 18:56

Quote: Originally posted by jimmyboy  

.. maybe the NaCl is just a catalyst but I think the problem is the dissociation constant of HCl

.. HCl, HBr, HI, HNO3, HClO3, HClO4 are the strong acids and always completely dissociate in solution .. so forming a strong acid with a weak one is next to impossible in solution since the dissociation is irreversible
.. hydronium and chloride ions will not reunite inside the water solution to form HCl acid under normal conditions .. so you will not get Hydrochloric
.. to prove it you just need distillation and use the boiling points of HCl and Acetic


This so garbled. :)

A mixture of a weak acid and the salt of a strong acid simply behaves like the solution of a weak acid, period.

Weaker acids cannot displace stronger ones from their salts.

Forget about distillation: the HCl-water azeotrope (at 20.2 % HCl) boils at 108.6 C: you'd be distilling off weak acetic acid, nothing more.

jimmyboy - 7-2-2016 at 19:46

Thanks for the confirmation Bloggy
.. there is quite a few Google results that say it forms the acid .. disappointing

[Edited on 8-2-2016 by jimmyboy]