[iScience]

So in the neutralization rxn between acetic acid and sodium bicarbonate, one of the products is sodium acetate.

If i understand correctly, the sodium acetate comes from the acetate anion and the sodium cation. but i thought the sodium cation was so stable that it doesn't bond with anything in an aqueous environment. At least that's what i've been told by multiple professors..

So what makes the sodium bond in this case?

[zsinger]

Close…..this is Na BOUND to another entity.  Not Na+. 
        -Zack

[zsinger]

How about Na+ with a high [Cl-] in an aqueous solution…..say 5 molar.  Principal species inventory!
       -Zack

[Arkcon]

Sometimes, when people ask what should be a simple question, then put on 2 or 3 disconnected qualifiers, it becomes hard to answer.  Please bear that in mind as we work through your question point by point.

So in the neutralization rxn between acetic acid and sodium bicarbonate, one of the products is sodium acetate.

If i understand correctly, the sodium acetate comes from the acetate anion and the sodium cation.

This is factual, clear and easy to follow.

but i thought the sodium cation was so stable that it doesn't bond with anything in an aqueous environment.

That statement doesn't make any sense.  What could unstable possibly mean, in the case of an elemental cation?  Maybe a polyatomic cation is unstable, maybe a radioactive element is atomically unstable, but that term makes no sense for the sodium cation.

At least that's what i've been told by multiple professors..

You'll have to give us the exact context of at least one of their statements, for the reasons I've highlighted above.

So what makes the sodium bond in this case?

You're also going to have to explain why you're asking this.  How do you think that an "unstable" cation won't form a bond?  The concepts are not exclusive.

Now, maybe here's where you're coming from.  In aqueous solution, there is no bond, the sodium cation and acetate anion float free.  But its not some inherent stability or instability that prevents it.  When the water evaporates, the solid sodium acetate will form.  Heated strongly, the acetate will burn, so maybe its "unstable."  But that doesn't really make a difference in solution.

[iScience]

What could unstable possibly mean, in the case of an elemental cation?

nooo, i wrote stable, not "unstable." but before i answer this let me answer this:

You'll have to give us the exact context of at least one of their statements, for the reasons I've highlighted above

(this was regarding my professors)

I can't provide any specific examples since i can't recall any. but basically for our O-chem class, we were predicting reactions for compounds with sodium in their formulae taking place in aqueous solution. I understood the steps that involved sodium becoming dissociated when you put the Na containing compound in water. But, i saw Na⁺ as an H⁺ equivalent (keep in mind this is when i was being exposed to O-chem for the first semester), so i asked my prof (multiple prof.s actually): why doesn't the Na⁺ get reduced by the reducers and form a bond? they replied, the sodium cation is more stable due to the satisfied octet configuration.

Okay... so that's the full story.

You're also going to have to explain why you're asking this.

Well, here's what i really wanted to get at

i was wondering, if the sodium acetate formed was like this (bound):



or like this (bonded)



oh, ignore the hydration

-----------

here's my conundrum: i was taught that sodium cations generally didn't get reduced to form bonds. Okay then, but see when i mix vinegar and baking soda together, i definitely do see a solid (really just looks alot like the Na-bicarbonate i dumped in... but anyway..). but i've also learned aboutf solubilities. where, if your solutes (Na⁺ and acetate^-) are polar in similar strengths with the solvent, then the solutes would be soluble.

Well...

my solute: Na⁺ and acetate^- (all polar)
my solvent: water (pretty polar)

So then why is my "solute" not dissolving? I shouldn't be able to see as much solid as i do when i mix the acid and base ingredients.


ty so much arkcon!!

[kriggy]

Well it might take some time to dissolve it all. Gently heating might fasten it. Given the fact that the solubility of sodium bicarbonate is not that high - 9g/L and vinegear is diluted acid, it might just be undisolved bicarbonate (maybe  you added too much of it)

[Arkcon]

Well, I'm understanding your confusion better now.  Yes, sodium has a more complete octet, and yes it is more resistant to redox.  But that's not the reaction you're getting, as you diagrammed in the second case.  You're getting an acid-base reaction to produce an ionic salt, as you diagrammed in the first example.  Yes, its an ionic salt that contains carbon, but the carboxylic acids, although weak acids, do behave very much like mineral acids, according to the Arrhenius definition of acid.

[iScience]

kriggy: you mean carbonic acid as opposed to bicarbonate? bicarbonate is an ion and would dissolve wouldn't it?




arkcon So, this sounds like it's nothing more than a case of an electrostatic interaction (as opposed to an actual ionic bond) that's just strong enough to keep the two ionic entities non-polar enough to keep it in tact (a solid) in water. Please confirm

Also, what about what kriggy said? the possibility does exist for the formation of carbonic acid.
(since i don't know where the equilibrium is: towards deprotination or protination) (although, i would guess towards deprotination simply cause it's called an acid lol)f

[kriggy]

No I ment bicarbonate.
Check this page - the tab on right side check solubility in water
http://en.wikipedia.org/wiki/Sodium_bicarbonate

So if you had like 50 ml of water and added 10g of bicarbonate some of it will not dissolve because the solution will be saturated

[orgopete]

I see two different interpretations that may apply.

Sodium chloride can be written as NaCl or Na⁺Cl^- and have the same meaning. No transfer of electrons has taken place and no covalent bond is present. If acetate were to replace chloride, it would be exactly the same. I think this is what the poster is asking about.

The other is a question that I have wondered about. If acetic acid is dissolved in water, only a fraction is ionized. If sodium acetate is dissolved in water, the solution is weakly basic. That is, a small number of acetate anions abstract a proton from water. I don't think of water as that strong of an acid, yet acetate can abstract a proton, though in low concentrations. If acetate is that strong as a base, then it seems plausible to me that some of the sodium ions may be bound to the acetate anions. Precipitation would indicate that at least kinetically an ionic bond has formed. It seems possible that some of the sodium acetate is bound in solution as ionic bonds. Is there a method that one determines the amount of ionization of a compound? In my manuscript, I argue pH or pKa determination is the best measure of ionization. That is, we seem to be able to measure proton affinities in solution, what about other Lewis acids? Are there other methods? Sorry, I just don't know this area. (Although I've used sodium acetate, I can imagine any number of substitutions to increase or decrease affinities.)

[Babcock_Hall]

here's my conundrum: i was taught that sodium cations generally didn't get reduced to form bonds. Okay then, but see when i mix vinegar and baking soda together, i definitely do see a solid (really just looks alot like the Na-bicarbonate i dumped in... but anyway..). but i've also learned aboutf solubilities. where, if your solutes (Na⁺ and acetate^-) are polar in similar strengths with the solvent, then the solutes would be soluble.

Sodium ions are rarely reduced, and it wouldn't happen in aqueous solution under any reasonable set of conditions that I can think of.  To be reduced, a sodium ion would have to gain an electron and become sodium metal.  If a sodium ion in aqueous solution forms a bond with an anion because the solution evaporates, I would not call this process a reduction.

[spirochete]

here's my conundrum: i was taught that sodium cations generally didn't get reduced to form bonds. Okay then, but see when i mix vinegar and baking soda together, i definitely do see a solid (really just looks alot like the Na-bicarbonate i dumped in... but anyway..). but i've also learned aboutf solubilities. where, if your solutes (Na⁺ and acetate^-) are polar in similar strengths with the solvent, then the solutes would be soluble.

Sodium ions are rarely reduced, and it wouldn't happen in aqueous solution under any reasonable set of conditions that I can think of.  To be reduced, a sodium ion would have to gain an electron and become sodium metal.  If a sodium ion in aqueous solution forms a bond with an anion because the solution evaporates, I would not call this process a reduction.

Definitely agree that an ionic bond between the sodium cation is not a reduction, neither in a formal sense or in a real chemical way. The oxidation state of sodium is plus one regardless. Sodium metal and chlorine gas are produced through electrolysis, but that of course requires a large energy input: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch20/faraday.php