The strongest acid...

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Offline Exodus

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The strongest acid...
« on: 24/04/2003 03:02:58 »
Can anyone tell me what the strongest acid known to man is, assuming each acid type is of similar molar concentration.[?]

Thats Economics...

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Offline NakedScientist

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Re: The strongest acid...
« Reply #1 on: 24/04/2003 11:12:34 »
Depends on what you mean by 'strong acid'. A 'strong' solution of acid might be a very concentrated one, but the acid itself might not be very 'strong', that is, very good at producing hydrogen ions. Also, it depends what you want to dissolve.

For instance, to get gold into solution you need aqua regia, a mixture of nitric (HNO3) and hydrochloric (HCl) acids. Neither acid on its own is sufficient to dissolve gold. http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/AQREGIA/PAGE1.HTM

On the other hand, to etch glass (for example to make 'frosted' light bulbs) you need hydrofluoric acid (HF).

As a general rule the better the 'acid' ionises, that is, the further the reaction moves to the right to make H+ ions, the stronger the acid. Strong acids like hydrochloric (HCl) ionise almost completely to H+ and Cl- ions in water, so all of the acidic component (the H+ ions) is available to react.

Examples of weak acids are things like vinegar or citric acid. These ionise only weakly with the majority of the 'acid' remaining unionised and only a small amount splitting up to make H+ ions and anions. As the hydrogen ions are used up by a reaction, more of the 'acid' ionises to replace them, but this takes time and limits the 'strength' of the acid.

Hope that helps.

TNS

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Offline cuso4

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Re: The strongest acid...
« Reply #2 on: 26/04/2003 07:56:36 »
What about H2SO4? Does this count as a strong acid?

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Offline Quantumcat

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Re: The strongest acid...
« Reply #3 on: 26/04/2003 09:33:46 »
H2SO4 is what the junior science classes use a lot. Surely it's not very strong :p
 

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Offline NakedScientist

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Re: The strongest acid...
« Reply #4 on: 26/04/2003 15:11:33 »
H2SO4 - sulphuric acid - is also a 'strong' acid which, like HCl, ionises very well in water and hence is a good source of H+ ions.
TNS

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Offline ducttapeman

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Re: The strongest acid...
« Reply #5 on: 09/07/2003 00:07:02 »
it depends, on how you are classing the acids, one of the strongest(on my scale), is the so called magic acid, FHSO3-SbF5, but only on it's reactivity, not so much on ionization in water, (i know its a little wierd but look it up)
 

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Offline chris

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Re: The strongest acid...
« Reply #6 on: 09/07/2003 23:40:24 »
Ducttapeman - Welcome

tell us a bit more about this bizarre acid of yours !

Chris

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Offline Supercryptid

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Re: The strongest acid...
« Reply #7 on: 17/02/2004 02:31:49 »
ducttapeman talks of fluoro-antimonic acid. It is a mixture of antimony pentafluoride and hydrogen fluoride. The ionization equation looks like this:

SbF5 + 2HF <--> SbF6- + H2F+

The antimony pentafluoride molecule takes a fluoride anion from a molecule of hydrogen fluoride. This leaves a proton behind, which seeks out another hydrogen fluoride molecule to form a fluoronium cation. This fluoronium cation is EXTREMELY acidic, and this is what causes the mixture to be so acidic.

I would expect a hypothetical hydrogen heliide cation to be even more acidic than a fluoronium cation because of helium's super-high electronegativity.

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Offline neilep

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Re: The strongest acid...
« Reply #8 on: 21/02/2004 03:47:18 »
Please realise that I am completely out of my depth here but could there be an acid which is so strong that it could not be stored in anything ?...it's just that I always remember seeing acids stored in glass containers, so is there an acid that can dissolve glass ?...and the acid portrayed in the Aliens films, does anything like that actually exist ?

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Offline Ylide

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Re: The strongest acid...
« Reply #9 on: 21/02/2004 04:26:39 »
Hydrofluoric acid will dissolve a glass container, as will sodium hydroxide (a strong base) albeit more slowly.  It has more to do with reactivity than strength.  Those materials are safely stored in Teflon or other organic polymer containers.  

I don't believe there exists a material that can't be stored SOMEWHERE.  Aqua Regia can dissolve gold but won't touch many transition metals.  There's always going to be something that is nonreactive to something else.

As far as the alien films, if those are steel floors and walls, many concentrated acids could do that.  An organism being able to protect itself from acid that concentrated is another story...even your stomach acid is thousands of times less powerful than that.

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Offline neilep

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Re: The strongest acid...
« Reply #10 on: 21/02/2004 13:33:09 »
Jay, fantastic, thank you very much.

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Offline tweener

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Re: The strongest acid...
« Reply #11 on: 22/02/2004 01:40:42 »
quote:
Originally posted by Quantumcat

H2SO4 is what the junior science classes use a lot. Surely it's not very strong :p



I got some H2SO4 on me when I was in chemistry class.  It felt REALLY strong then!

As for a substance that can't be stored in anything, how would we know about it if we can't store it and study it?  One thing that comes to mind is some of the plasma from the interior of the sun. I can't think of any way to store it except in a very strong gravitic field such as the interior of a star.


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Offline Ylide

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Re: The strongest acid...
« Reply #12 on: 22/02/2004 04:32:55 »
Wouldn't that plasma cool down when taken out of the environment of the sun?  Of course, how you're going to get it out of there in the first place is another story.  [:P]



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Offline tweener

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Re: The strongest acid...
« Reply #13 on: 23/02/2004 03:24:56 »
I suppose it would cool quite fast, but I have no idea how to get to it, let alone get it out.


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Offline Ylide

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Re: The strongest acid...
« Reply #14 on: 23/02/2004 17:40:32 »
Maybe if we built this giant wooden badger....

sorry, watched Monty Python and the Holy Grail last night.  Couldn't be helped.  [:P]



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Offline tweener

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Re: The strongest acid...
« Reply #15 on: 23/02/2004 19:22:35 »
hehehehe - It'd be fun to watch it flame out somewhere around the orbit of venus!


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Offline Quantumcat

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Re: The strongest acid...
« Reply #16 on: 23/02/2004 19:47:25 »
I didn't read all the post, but acidobasic reactions is what the class is working on at the moment and I don't understand it at all ... ~sighs~

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Offline Supercryptid

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Re: The strongest acid...
« Reply #17 on: 24/02/2004 04:14:53 »
So far to my knowledge, the hypothetically most powerful acid would be NeH4^4+. It would consist of a neon atom in the sp3 hybridization state, and each of the four lone pairs would form a coordinate bond with a proton, forming a tetrahedral molecule similar to methane in appearance.

This cation would be EXTREMELY unstable, and would immediately discard all four of those protons. In fact, it would probably be so unstable that it could never be synthesized.

This makes me wonder if other similar cations might be formed someday, such as H4O^2+ and H4F^3+. I doubt the positively charged hydronium cation would be able to act as a lewis base to a proton though, since both of them are positively charged and would repel one another. These hypothetical molecules would also be super-powerful acidic molecules.
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Offline cuso4

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Re: The strongest acid...
« Reply #18 on: 24/02/2004 09:14:48 »
quote:
Originally posted by Quantumcat

I didn't read all the post, but acidobasic reactions is what the class is working on at the moment and I don't understand it at all ... ~sighs~

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You're not doing titration reactions, are you?
acid + alkali -> salt + water?

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Offline NickNYC

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Re: The strongest acid...
« Reply #19 on: 11/03/2004 18:45:39 »
THE strongest acid, much to all of your surprise I'm sure is actually synthesizedin the human stomach.  YES, the reaction occurs quite precisely 3.257 minutes after completing any item on the menu of Speedo's Taqueria on Madison Avenue in Albany, NY.  Now, if we could only harness this power... think of all they dissolving things we could do! Just THINK of it man!

good day.
 

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Offline Donnah

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Re: The strongest acid...
« Reply #20 on: 11/03/2004 22:58:25 »
Guess I can't think of it.  I'm not a man.
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Offline Ylide

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Re: The strongest acid...
« Reply #21 on: 12/03/2004 17:38:23 »
Nick, I would say the reaction obtained from eating at any sleazy mexican place on the east coast (you guys know mexican like we know pizza...not at all!) is a result of the added material in the food.  Note how the same thing doesn't occur when you plow through a pizza or a cheesesteak.  

Glad to see a fellow new yorker here (even though I don't live there anymore!)




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Offline NickNYC

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Re: The strongest acid...
« Reply #22 on: 15/03/2004 18:10:32 »
yeah.. this is a bad UPstate mex place.. the best mexican round these parts is a place called Rosa Mexicano in manhattan.. upper east side i believe... they make the best guacamole EVER and they make it AT your table.

yes, donnah, you're strictly forbidden to think about it because of your woman-ness... that is exactly what i intended and i'm glad you caught that and didn't just go ahead and think of anything because that would be wrong.

 

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Offline Donnah

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Re: The strongest acid...
« Reply #23 on: 17/03/2004 01:39:22 »
quote:
Originally posted by NickNYC
yes, donnah, you're strictly forbidden to think about it because of your woman-ness... that is exactly what i intended and i'm glad you caught that and didn't just go ahead and think of anything because that would be wrong.


Yes NickNYC, we mere women cannot possibly think as well as men.  They have two heads to our one after all, and we know what wonderful decisions men make with the aid of that second head.[;)]
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Offline MayoFlyFarmer

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Re: The strongest acid...
« Reply #24 on: 21/03/2004 00:25:30 »
cuso, you sound like you have the same tramitization from titration rxns that I do.  (shutters).  It took all my strength just to open the "cehmistry" section on this site. (and now I'm leaving!)

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Offline neilep

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Re: The strongest acid...
« Reply #25 on: 21/03/2004 03:39:59 »
quote:
Originally posted by Donnah

quote:
Originally posted by NickNYC
yes, donnah, you're strictly forbidden to think about it because of your woman-ness... that is exactly what i intended and i'm glad you caught that and didn't just go ahead and think of anything because that would be wrong.


Yes NickNYC, we mere women cannot possibly think as well as men.  They have two heads to our one after all, and we know what wonderful decisions men make with the aid of that second head.[;)]




Thanks Donnah, that's really supportive of you[:)][;)], and as males we appreciate your kind understanding and concurrence [:D]......I just hate it though ,when one head does not do what the other one wants it to do...errhmmmm!![:)][:I][:I]

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Offline MayoFlyFarmer

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Re: The strongest acid...
« Reply #26 on: 21/03/2004 05:30:42 »
[:0][:p]  that could have SO many meanings, NONE of which I was prepared for!

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Offline ruthenium

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Re: The strongest acid...
« Reply #27 on: 04/04/2004 21:46:47 »
HJ is the strongest acid among simple, mineral acids
 

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Offline CsManiacDan

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Re: The strongest acid...
« Reply #28 on: 05/04/2004 09:12:53 »
What's Element J? I wasn't aware of an element having the symbol J.

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Offline MayoFlyFarmer

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Re: The strongest acid...
« Reply #29 on: 05/04/2004 13:55:47 »
thank you for asking that, I thought I was even dumber at chemistry than I had previously thought I was.  So...what is "J"??

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Offline gsmollin

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Re: The strongest acid...
« Reply #30 on: 05/04/2004 20:20:30 »
I think ruthenium means HF.
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Offline ruthenium

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Re: The strongest acid...
« Reply #31 on: 05/04/2004 20:59:02 »
Sorry, it is HI
 

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Offline Big_Jules

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Re: The strongest acid...
« Reply #32 on: 09/04/2004 03:18:15 »
I'd like to go right back to Chris' very early comment regarding conception of strength. In distilled water, all 'strong' mineral acids dissocite fully, while many of the weak organic acids dissociate only partially, though that does depend on actual concentration of any given acid, and the resulting pH). As he indicated, strnegth by this definition relates to the ability to generate hydrogen ions, the concentration of which defines pH in a model system.

I'd like to take another angle. Organic acids are used quite widely, either through addition or generation during fermentation processes, as antimicrobial preservatives in foods. At a given, moderate pH, such organic acids prove more effective and could thus be viewed as 'stronger' than  mineral acids in preventing the growth of microorganisms. This is due to the partitioning of dissociated and undissociated acids between the external and internal cell environment, respectively. Undissociated acids (e.g. acetic acid as CH3COOH, rather than CH3COO- and H+) are taken up passively by bugs and accumulate in the cell, lowering pH. The cell has to expend a lot of energy to pump the acid out of the cell. If sufficient acid exists in the food product, it continues to flow into the cell, which eventually becomes exhausted, acid accumulates sufficiently to destroy key cell functions and the cell dies. Imagine being in a boat with a hole in it and having to continually bail out water. Eventually, you get too tired, the boat sinks and you drown! As mineral acids do dissociate, they don't 'behave' this way. If they are used in sufficient concentration to lower external pH sufficiently, then there will be a killing effect, but by then the food is probably too acid to be enjoyable!
 

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Offline chris

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Re: The strongest acid...
« Reply #33 on: 09/04/2004 05:56:06 »
Nicely put. So the mineral acids in their non-dissociated form - e.g. vinegar CH3.COOH - can move readily across the lipid membrane (because they are uncharged) of cells. Within the intracellular environment they then dissociate - CH3.COOH -> CH3.COO - + H+ and impede cellular functions in contaminating microbes. Brilliant.

There is actually a human correlate and that's the example of aspirin (acetyl salicylate), which is itself a weak acid. In the stomach, where there is a lot of acid) the aspirin molecule remains un-ionised - in other words it mops up hydrogen ions (H+) - and stays in its uncharged form. In this form it can cross the stomach wall, by using the fact that it is an organic molecule to 'soak' through the lipid in the stomach cell membranes and into the blood stream. Once in the blood (where the pH is weakly alkaline - about 7.4 in an artery - it ionises).

Hence aspirin is one of the few drugs able to be directly absorbed through the stomach wall where most agents rely on the intestine to pick them up.

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Offline ruthenium

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Re: The strongest acid...
« Reply #34 on: 04/04/2004 21:46:47 »
HJ is the strongest acid among simple, mineral acids
 

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Offline CsManiacDan

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Re: The strongest acid...
« Reply #35 on: 05/04/2004 09:12:53 »
What's Element J? I wasn't aware of an element having the symbol J.

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Offline MayoFlyFarmer

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Re: The strongest acid...
« Reply #36 on: 05/04/2004 13:55:47 »
thank you for asking that, I thought I was even dumber at chemistry than I had previously thought I was.  So...what is "J"??

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Offline gsmollin

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Re: The strongest acid...
« Reply #37 on: 05/04/2004 20:20:30 »
I think ruthenium means HF.
"F = ma, E = mc^2, and you can't push a string."

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Offline ruthenium

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Re: The strongest acid...
« Reply #38 on: 05/04/2004 20:59:02 »
Sorry, it is HI
 

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Offline Big_Jules

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Re: The strongest acid...
« Reply #39 on: 09/04/2004 03:18:15 »
I'd like to go right back to Chris' very early comment regarding conception of strength. In distilled water, all 'strong' mineral acids dissocite fully, while many of the weak organic acids dissociate only partially, though that does depend on actual concentration of any given acid, and the resulting pH). As he indicated, strnegth by this definition relates to the ability to generate hydrogen ions, the concentration of which defines pH in a model system.

I'd like to take another angle. Organic acids are used quite widely, either through addition or generation during fermentation processes, as antimicrobial preservatives in foods. At a given, moderate pH, such organic acids prove more effective and could thus be viewed as 'stronger' than  mineral acids in preventing the growth of microorganisms. This is due to the partitioning of dissociated and undissociated acids between the external and internal cell environment, respectively. Undissociated acids (e.g. acetic acid as CH3COOH, rather than CH3COO- and H+) are taken up passively by bugs and accumulate in the cell, lowering pH. The cell has to expend a lot of energy to pump the acid out of the cell. If sufficient acid exists in the food product, it continues to flow into the cell, which eventually becomes exhausted, acid accumulates sufficiently to destroy key cell functions and the cell dies. Imagine being in a boat with a hole in it and having to continually bail out water. Eventually, you get too tired, the boat sinks and you drown! As mineral acids do dissociate, they don't 'behave' this way. If they are used in sufficient concentration to lower external pH sufficiently, then there will be a killing effect, but by then the food is probably too acid to be enjoyable!
 

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Offline chris

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Re: The strongest acid...
« Reply #40 on: 09/04/2004 05:56:06 »
Nicely put. So the mineral acids in their non-dissociated form - e.g. vinegar CH3.COOH - can move readily across the lipid membrane (because they are uncharged) of cells. Within the intracellular environment they then dissociate - CH3.COOH -> CH3.COO - + H+ and impede cellular functions in contaminating microbes. Brilliant.

There is actually a human correlate and that's the example of aspirin (acetyl salicylate), which is itself a weak acid. In the stomach, where there is a lot of acid) the aspirin molecule remains un-ionised - in other words it mops up hydrogen ions (H+) - and stays in its uncharged form. In this form it can cross the stomach wall, by using the fact that it is an organic molecule to 'soak' through the lipid in the stomach cell membranes and into the blood stream. Once in the blood (where the pH is weakly alkaline - about 7.4 in an artery - it ionises).

Hence aspirin is one of the few drugs able to be directly absorbed through the stomach wall where most agents rely on the intestine to pick them up.

Chris

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Offline lightarrow

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Re: The strongest acid...
« Reply #41 on: 26/08/2006 23:13:22 »
quote:
Originally posted by Exodus

Can anyone tell me what the strongest acid known to man is, assuming each acid type is of similar molar concentration.[?]
Let's go a bit into science-fiction.

the strongest acid I could think of is...antimatter.

I explain: according to Lewis definition of acidity (more general than the Brownsted one with protons only) an acid is a substance which reacts with another substance's electrons to form a bond. What does react with a substance's electrons more than antielectrons?

You know, when an antielectron approach enough an electron, they disintegrate each other generating a flash of light energy.
(The same with protons and antiprotons)

Incidentally, that would also be the most reactive acid!

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Offline Mjhavok

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Re: The strongest acid...
« Reply #42 on: 30/08/2006 02:59:43 »
In general scientific usage an acid is a molecule or ion that is able to give up a proton (H+ ion) to a base, or accept an unshared pair of electrons from a base. An acid reacts with a base in a neutralization reaction to form a salt.
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Offline bostjan

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Re: The strongest acid...
« Reply #43 on: 30/08/2006 06:28:25 »
wouldn't the strongest acid be h3o+?  i know nothing of chemistry.
 

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Offline lightarrow

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Re: The strongest acid...
« Reply #44 on: 30/08/2006 15:46:32 »
In general scientific usage an acid is a molecule or ion that is able to give up a proton (H+ ion) to a base, or accept an unshared pair of electrons from a base. An acid reacts with a base in a neutralization reaction to form a salt.

What does exactly mean "...accept an ushared pair of electrons..."?

...It means that it forms a bond with them, and to do it it must take the other specie's electrons!

What does exactly mean "...from a base"? That is, what's exactly a "base"?

It's something able to give its electrons to another species.

In the reaction between an acid and a base, there could form a salt but it could also NOT form any salt! I could make a lot of examples of this, but I'll write only some:

Al3+ + 3H2O --> Al(OH)3 + 3H+ ; Al3+ is the acid and water is the base.

H2SO4 + CH3COOH --> CH3COOH2+ + HSO4- ; H2SO4 is the acid, CH3COOH (acetic acid) is the base!

NH3 + H2O --> NH4+ + OH- ; H2O is the acid, NH3 is the base...

« Last Edit: 07/11/2007 16:42:35 by lightarrow »

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Re: The strongest acid...
« Reply #45 on: 30/08/2006 16:38:39 »
quote:
Originally posted by bostjan

wouldn't the strongest acid be h3o+?  i know nothing of chemistry.
This is true only if all the chemical species you are considering are in dilute acqueous solution. Infact, since the water molecule can act as a base (electron pairs on the outer of the oxygen atom), if there existed a stronger acid than H3O+, it would react with water molecules forming H3O+ :

HA + H2O <--> H3O+ + A- ; for protic acids
Acid + 2H2O <--> AcidOH- + H3O+ ; for other acids.

Anyway, from the equilibriums above, we can understand if an acid is stronger than H3O+ : if the reaction is shifted to the right (I'm sorry, I don't know how to translate this exactly into english) then it's stronger than H3O+ , weaker in the opposite case.

Example: which is stronger, HCl or H3O+ ? Amswer: HCl. Why? Because:

HCl + H2O --> H3O+ + Cl- . In this case I didn't wrote two arrows, because the reaction is shifted (goes) completely on the right. So, HCl is much stronger than H3O+.

Wikipedia (http://en.wikipedia.org/wiki/Strong_acid) gives this range of acidity :
Hydroiodic acid HI > Hydrobromic acid HBr > Hydrochloric acid HCl > Perchloric acid HClO4 > Sulfuric acid H2SO4 (Ka1/first dissociation only) > Nitric acid HNO3 > Hydronium ion H3O+.

To measure the acidity of very strong acids, so, it's better to use chemical species less basic than water, for example CH3COOH, because in this case the equilibrium is not completely shifted on the right.

The acidity, then, can be expressed with the "Hammett acidity function".
« Last Edit: 30/08/2006 16:51:48 by lightarrow »

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Re: The strongest acid...
« Reply #46 on: 31/08/2006 05:40:15 »
ahh, i see.  very good response.
 

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Re: The strongest acid...
« Reply #47 on: 30/08/2006 06:28:25 »
wouldn't the strongest acid be h3o+?  i know nothing of chemistry.
 

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Re: The strongest acid...
« Reply #48 on: 30/08/2006 15:46:32 »
quote:
Originally posted by Mjhavok

In general scientific usage an acid is a molecule or ion that is able to give up a proton (H+ ion) to a base, or accept an unshared pair of electrons from a base. An acid reacts with a base in a neutralization reaction to form a salt.
What does exactly mean "...accept an ushared pair of electrons..."?

...It means that it forms a bond with them, and to do it it must take the other specie's electrons!

What does exactly mean "...from a base"? That is, what's exactly a "base"?

It's something able to give its electrons to another species.

In the reaction between an acid and a base, there could form a salt but it could also NOT form any salt! I could make a lot of examples of this, but I'll write only some:

Al3+ + 3H2O --> Al(OH)3 + 3H+ ; Al3+ is the acid and water is the base.

H2SO4 + CH3COOH --> CH3COOH2+ + HSO4- ; H2SO4 is the acid, CH3COOH (acetic acid) is the base!

NH3 + H2O --> NH4+ + OH- ; H2O is the acid, NH3 is the base...


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Re: The strongest acid...
« Reply #49 on: 30/08/2006 16:38:39 »
quote:
Originally posted by bostjan

wouldn't the strongest acid be h3o+?  i know nothing of chemistry.
This is true only if all the chemical species you are considering are in dilute acqueous solution. Infact, since the water molecule can act as a base (electron pairs on the outer of the oxygen atom), if there existed a stronger acid than H3O+, it would react with water molecules forming H3O+ :

HA + H2O <--> H3O+ + A- ; for protic acids
Acid + 2H2O <--> AcidOH- + H3O+ ; for other acids.

Anyway, from the equilibriums above, we can understand if an acid is stronger than H3O+ : if the reaction is shifted to the right (I'm sorry, I don't know how to translate this exactly into english) then it's stronger than H3O+ , weaker in the opposite case.

Example: which is stronger, HCl or H3O+ ? Amswer: HCl. Why? Because:

HCl + H2O --> H3O+ + Cl- . In this case I didn't wrote two arrows, because the reaction is shifted (goes) completely on the right. So, HCl is much stronger than H3O+.

Wikipedia (http://en.wikipedia.org/wiki/Strong_acid) gives this range of acidity :
Hydroiodic acid HI > Hydrobromic acid HBr > Hydrochloric acid HCl > Perchloric acid HClO4 > Sulfuric acid H2SO4 (Ka1/first dissociation only) > Nitric acid HNO3 > Hydronium ion H3O+.

To measure the acidity of very strong acids, so, it's better to use chemical species less basic than water, for example CH3COOH, because in this case the equilibrium is not completely shifted on the right.

The acidity, then, can be expressed with the "Hammett acidity function".
« Last Edit: 30/08/2006 16:51:48 by lightarrow »