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Non Life Sciences => Chemistry => Topic started by: Exodus on 24/04/2003 03:02:58

Title: The strongest acid...
Post by: Exodus 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...
Title: Re: The strongest acid...
Post by: NakedScientist 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
Title: Re: The strongest acid...
Post by: cuso4 on 26/04/2003 07:56:36
What about H2SO4? Does this count as a strong acid?

AG
Title: Re: The strongest acid...
Post by: Quantumcat on 26/04/2003 09:33:46
H2SO4 is what the junior science classes use a lot. Surely it's not very strong :p
Title: Re: The strongest acid...
Post by: NakedScientist 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
Title: Re: The strongest acid...
Post by: ducttapeman 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)
Title: Re: The strongest acid...
Post by: chris on 09/07/2003 23:40:24
Ducttapeman - Welcome

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

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx
Title: Re: The strongest acid...
Post by: Kryptid 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.

Title: Re: The strongest acid...
Post by: neilep 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 ?

'Men are the same as women...just inside out !'
Title: Re: The strongest acid...
Post by: Ylide 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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Title: Re: The strongest acid...
Post by: neilep on 21/02/2004 13:33:09
Jay, fantastic, thank you very much.

'Men are the same as women...just inside out !'
Title: Re: The strongest acid...
Post by: tweener 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.


----
John
Title: Re: The strongest acid...
Post by: Ylide 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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Title: Re: The strongest acid...
Post by: tweener 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.


----
John
Title: Re: The strongest acid...
Post by: Ylide 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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Title: Re: The strongest acid...
Post by: tweener on 23/02/2004 19:22:35
hehehehe - It'd be fun to watch it flame out somewhere around the orbit of venus!


----
John
Title: Re: The strongest acid...
Post by: Quantumcat 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~

Am I dead? Am I alive? I'm both!
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Title: Re: The strongest acid...
Post by: Kryptid 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.
Title: Re: The strongest acid...
Post by: cuso4 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~

Am I dead? Am I alive? I'm both!
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You're not doing titration reactions, are you?
acid + alkali -> salt + water?

Angel
Title: Re: The strongest acid...
Post by: NickNYC 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.
Title: Re: The strongest acid...
Post by: Donnah on 11/03/2004 22:58:25
Guess I can't think of it.  I'm not a man.
Title: Re: The strongest acid...
Post by: Ylide 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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Title: Re: The strongest acid...
Post by: NickNYC 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.

Title: Re: The strongest acid...
Post by: Donnah 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.[;)]
Title: Re: The strongest acid...
Post by: MayoFlyFarmer 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!)

Yar, the flies be everywhere maty....save yerselves!!!
Title: Re: The strongest acid...
Post by: neilep 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]

'Men are the same as women...just inside out !'
Title: Re: The strongest acid...
Post by: MayoFlyFarmer on 21/03/2004 05:30:42
[:0][:p]  that could have SO many meanings, NONE of which I was prepared for!

Yar, the flies be everywhere maty....save yerselves!!!
Title: Re: The strongest acid...
Post by: ruthenium on 04/04/2004 21:46:47
HJ is the strongest acid among simple, mineral acids
Title: Re: The strongest acid...
Post by: CsManiacDan on 05/04/2004 09:12:53
What's Element J? I wasn't aware of an element having the symbol J.

I Love Caesium!!!
Title: Re: The strongest acid...
Post by: MayoFlyFarmer 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"??

This is a signature.... AND YOU WILL LIKE IT!!
Title: Re: The strongest acid...
Post by: gsmollin on 05/04/2004 20:20:30
I think ruthenium means HF.
Title: Re: The strongest acid...
Post by: ruthenium on 05/04/2004 20:59:02
Sorry, it is HI
Title: Re: The strongest acid...
Post by: Big_Jules 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!
Title: Re: The strongest acid...
Post by: chris 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

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx
Title: Re: The strongest acid...
Post by: ruthenium on 04/04/2004 21:46:47
HJ is the strongest acid among simple, mineral acids
Title: Re: The strongest acid...
Post by: CsManiacDan on 05/04/2004 09:12:53
What's Element J? I wasn't aware of an element having the symbol J.

I Love Caesium!!!
Title: Re: The strongest acid...
Post by: MayoFlyFarmer 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"??

This is a signature.... AND YOU WILL LIKE IT!!
Title: Re: The strongest acid...
Post by: gsmollin on 05/04/2004 20:20:30
I think ruthenium means HF.
Title: Re: The strongest acid...
Post by: ruthenium on 05/04/2004 20:59:02
Sorry, it is HI
Title: Re: The strongest acid...
Post by: Big_Jules 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!
Title: Re: The strongest acid...
Post by: chris 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

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx
Title: Re: The strongest acid...
Post by: lightarrow 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!
Title: Re: The strongest acid...
Post by: Mjhavok 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.
Title: Re: The strongest acid...
Post by: bostjan on 30/08/2006 06:28:25
wouldn't the strongest acid be h3o+?  i know nothing of chemistry.
Title: Re: The strongest acid...
Post by: lightarrow 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...

Title: Re: The strongest acid...
Post by: lightarrow 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".
Title: Re: The strongest acid...
Post by: bostjan on 31/08/2006 05:40:15
ahh, i see.  very good response.
Title: Re: The strongest acid...
Post by: bostjan on 30/08/2006 06:28:25
wouldn't the strongest acid be h3o+?  i know nothing of chemistry.
Title: Re: The strongest acid...
Post by: lightarrow 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...

Title: Re: The strongest acid...
Post by: lightarrow 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".
Title: Re: The strongest acid...
Post by: bostjan on 31/08/2006 05:40:15
ahh, i see.  very good response.
Title: Re: The strongest acid...
Post by: dtx on 02/10/2006 14:42:22
As was stated, a "strong" acid refers only to its ability to completely dissociate into ions; most of the non-chemist people reading this take an acid's strength to mean its ability burn/dissolve/melt "stuff."  Even using the non-technical definition there aren't any easy to understand general rules about reactivity (see aqua regia for an interesting read).  For example, if you want to act on Cu, 12M HCl (which will melt your face off) won't give you much of a show at all :)  But, 1M HNO3 is quite a different story.  Also, different acids have different vapor pressures, so sustainable concentration can be an issue.  See how long 95% HCl stays that way in an open bottle.  Hint: do it under a hood!

Another fun fact: "pure" H20 always and forever contains a very low concentration of H30+ and OH- ions.

lightarrow, shifted is indeed the correct word.
Title: Re: The strongest acid...
Post by: Mr Andrew on 03/10/2006 20:51:04
I did a little research on the topic of superacids and here's what I found.  Basically, superacids are just as the name implies, they are super strong acids (typically both definitions apply here but the one about being highly dissociated is the one I am referring to when I say strong).  Generally they are complexes of several acids together.  I'm not quite sure if aqua regia counts because I'm not sure whether it's a complex or not.  Anyway, the strongest one known is SbF5 HF.  This acid is extremely strong as it forms a proton and an SbF6+ ion.  I believe also that in the right concentrations it forms H2F+ ions or HF2- ions.  This is really strong stuff![}:)]

"His mind is the ultimate weapon!"-MacGyver television series
Title: Re: The strongest acid...
Post by: lightarrow on 10/10/2006 14:41:22
Aqua regia is less strong than HCl because HCl is diluted with HNO3 (less acid than HCl) and because they partially react:
3HCl + HNO3 --> NOCl + CL2 + 2H2O

The ability of aqua regia to dissolve gold, as well as many others metals, is principally due to the oxidizing power of CL2, the acidity of the solution and the complexing power of Cl- ions:
Au3+ + 4Cl- --> AuCl4-, for example.

In a book I have it's stated that, as a prove of this, a solution of HCl and oxigenated water has a similar dissolving power than aqua regia.
Title: Re: The strongest acid...
Post by: Heliotrope on 12/11/2006 19:00:29
It's not really an acid but as I recall the most "acidic" substance is liquid boron.
It's melting point is very high so anything you put it into will melt long before the boron does. It will also eat it's way through anything you put it in.
I'll see if I can find the article I read.
Title: Re: The strongest acid...
Post by: Heliotrope on 12/11/2006 19:01:56
Found it : http://focus.aps.org/story/v2/st4

Title: Re: The strongest acid...
Post by: lightarrow on 13/11/2006 14:13:11
It's not really an acid but as I recall the most "acidic" substance is liquid boron.
It's melting point is very high so anything you put it into will melt long before the boron does. It will also eat it's way through anything you put it in.
I'll see if I can find the article I read.

I don't think that, from that article, it could be sad that liquid boron is the most acidic substance, but simply that, at 2300°C, it attacks almost everything, which doesn't surprise me, considered that temperature, and the little atomic radius of boron. Liquid carbon (which exist only at high pressures) or liquid Berillium, at the same temperature, would behave in a similar way, I suspect.
Title: Re: The strongest acid...
Post by: Heliotrope on 13/11/2006 21:15:27
Well I did say that it wasn't really an acid.
And you're probably right, they might very well behave in a similar way. This was the only article I'd read that concerns something that can't be held in anything however.
Not the sort of stuff you'd like to have melting it's way through your pulse rifle after zapping the thing that was using it for blood anyway. [:D]

I also thought that Perchloric acid was supposed to be the stongest proper acid.
Is that not correct ?
My chemistry is rather weak I'm afraid.
Title: Re: The strongest acid...
Post by: lightarrow on 14/11/2006 14:47:31
It doesn't seem there is good agreement among references:

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+.

From another source http://venus.unive.it/chem2000/capitoli/24.htm:

HClO4 > HMnO4 > HClO3 > H2SeO4 > HI > HBr > HCl > HSO4- > HClO2 > HNO2 > HF.

What I have learned at univ. :

HClO4 ≈ H2SO4 (concentrated, 1° dissociation) > HI > HBr > HCl > HNO3 > H3O+ > Oxalic Acid > HF > CH3COOH > H2S.


Title: Re: The strongest acid...
Post by: Heliotrope on 14/11/2006 19:55:49
Quote from: Wikipedia
The carborane superacid (H(CHB11Cl11), which is one million times stronger than sulfuric acid, is entirely non-corrosive, whereas the weak acid hydrofluoric acid (HF) is extremely corrosive and can dissolve, among other things, glass, and all metals except iridium.

I didn't realise there was a distinction between being acidic and being corrosive.
I thought that the stronger the acid got, the more corrosive it was.
As I said, chemistry is not my strong suit.

Title: Re: The strongest acid...
Post by: lightarrow on 15/11/2006 13:55:17
Quote from: Wikipedia
The carborane superacid (H(CHB11Cl11), which is one million times stronger than sulfuric acid, is entirely non-corrosive, whereas the weak acid hydrofluoric acid (HF) is extremely corrosive and can dissolve, among other things, glass, and all metals except iridium.
I didn't realise there was a distinction between being acidic and being corrosive.
I thought that the stronger the acid got, the more corrosive it was.
As I said, chemistry is not my strong suit.


Corrosive means able to dissolve some substance, so it depends on which substance. For example, HNO3 is very corrosive for iron, copper, silver, tin, plumb, mercury, but non-corrosive at all for aluminum. NaOH is corrosive for aluminum, but not for iron, HCl is very corrosive for aluminum and, less, for iron, but not for silver, copper, plumb...

Acidic means able to give H+ ions (Bronsted acidity) or, more generally, able to form a stable bond with lonely electron pairs of an atom (Lewis acidity).
Title: Re: The strongest acid...
Post by: Heliotrope on 17/11/2006 21:16:44
Gotcha.
Thanks.
[:)]
Title: Re: The strongest acid...
Post by: Mr Andrew on 17/12/2006 18:00:17
lightarrow, just as a matter of technicality, your plumb is called lead in english.  I don't know why, plumb makes much more sense because the latin was plumbus and the symbol is Pb.  I thought I might let you know just so no one gets confused.  Oh, and just because I'm curious, what is lead in italian?

Anyway, more about corrosivity and causticity.  What is causticity if corrosivity is how readily something reacts with a metal?  How corrosive of aluminum is KOH?  If it is strongly corrosive then I wonder why it took at least 40 minutes for it to react with the aluminum cans that we used to synthesize alum?  It was 3 molar KOH.  We scratched up the surfaces of the aluminum cans so that any paint or other coatings would not inhibit the reaction and it still didn't go quickly.  Could it be possible that the can was made of an alloy of some sort with very little aluminum?
Title: Re: The strongest acid...
Post by: lightarrow on 19/12/2006 19:41:28
lightarrow, just as a matter of technicality, your plumb is called lead in english.
Of course! Thank you to have reminded me!
Quote
I don't know why, plumb makes much more sense because the latin was plumbus and the symbol is Pb.  I thought I might let you know just so no one gets confused.  Oh, and just because I'm curious, what is lead in italian?
Lead = Piombo, in italian.
Quote
Anyway, more about corrosivity and causticity.  What is causticity if corrosivity is how readily something reacts with a metal?  How corrosive of aluminum is KOH?  If it is strongly corrosive then I wonder why it took at least 40 minutes for it to react with the aluminum cans that we used to synthesize alum?  It was 3 molar KOH.  We scratched up the surfaces of the aluminum cans so that any paint or other coatings would not inhibit the reaction and it still didn't go quickly.  Could it be possible that the can was made of an alloy of some sort with very little aluminum?
Probably NaOH is more corrosive for Al than KOH, but I'm not sure of it, never tried with KOH. However, it also depends on the overall amount of the solution: if it's little (enough to react with all the Al), the reaction is faster because the temperature reached is higher.
I've never tried with cans; I don't know their exact composition, maybe the alloy is more resistant to alkaly than pure Al.
Title: The strongest acid...
Post by: Weldmann on 13/08/2007 12:04:15
What is the best acid for quickly dissolving ferrous metals that is not too exotic and readily available?
Title: The strongest acid...
Post by: lightarrow on 13/08/2007 17:42:56
What is the best acid for quickly dissolving ferrous metals that is not too exotic and readily available?
"Ferrous metals" it's too generic: if you mean the common iron used for nails, ecc, then it's HNO3 (diluted a little). If you mean steels, it depends on the kind of steel; usually acqua regia, if it's stainless steel, for example (with a bit of HF, if you have).
At higher temperatures it's ok even HCl (at least for iron).
Title: The strongest acid...
Post by: vinuuraj on 07/11/2007 16:16:10
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.
Title: The strongest acid...
Post by: Bored chemist on 07/11/2007 19:22:08
Conc nitric (above about 7M) passivates stainless steel. Adding HCl will dissolve the steel better in some cases. Warm HCl is pretty good but, as always, the devil is in the details. Exacly what alloy do you want to dissolve?
Title: The strongest acid...
Post by: Wally on 20/11/2007 00:14:49
Hi passionated Scientists, greetings from México, from the UNAM:

I´m new in this page, but I'd like to help with this question

It is well known for us that there are several strong acids like the H2SO4 or HCl, but reviewing in some books of Organic Chemistry as Mohrig´s I found there are some acids stronger than the sulfuric acid, I mean the called "superacids", see this page: http://en.wikipedia.org/wiki/Superacids

You can compare their ionization constants, for example for the triflic acid(trifluoromethanesulfonic acid) is Ka = 8.0 *1014 mole kg-1 CF3SO3H; for the Fluorosulfuric acid k= 10000000000 and for the sulfuric acid K1 = 2.4 * 106, there are another acids stronger than the sulfuric acid and you can compare them by yourself in http://www.jenck.com/t-acidez.htm., obviusly triflic acid is much stronger than the sulfuric one.

Now, the strongest acid I know is the triflic acid, and be very carefull with the chlorosulfonic acid when you work in the laboratory, it burns¡¡¡¡¡

I almost forgot it, keep in mind that the acidity of one acid depends too on the solvent in which it is dissolved, if the solvent is polar or non polar affects the acidity, so,perhaps you will need to learn some about analitical chemistry to understand this.

see also: http://en.wikipedia.org/wiki/Triflic_acid

I hope this helps
Title: The strongest acid...
Post by: lightarrow on 20/11/2007 15:22:41
Hi passionated Scientists, greetings from México, from the UNAM:

I´m new in this page, but I'd like to help with this question

It is well known for us that there are several strong acids like the H2SO4 or HCl, but reviewing in some books of Organic Chemistry as Mohrig´s I found there are some acids stronger than the sulfuric acid, I mean the called "superacids", see this page: http://en.wikipedia.org/wiki/Superacids

You can compare their ionization constants, for example for the triflic acid(trifluoromethanesulfonic acid) is Ka = 8.0 *1014 mole kg-1 CF3SO3H; for the Fluorosulfuric acid k= 10000000000 and for the sulfuric acid K1 = 2.4 * 106, there are another acids stronger than the sulfuric acid and you can compare them by yourself in http://www.jenck.com/t-acidez.htm., obviusly triflic acid is much stronger than the sulfuric one.

Now, the strongest acid I know is the triflic acid, and be very carefull with the chlorosulfonic acid when you work in the laboratory, it burns¡¡¡¡¡

I almost forgot it, keep in mind that the acidity of one acid depends too on the solvent in which it is dissolved, if the solvent is polar or non polar affects the acidity, so,perhaps you will need to learn some about analitical chemistry to understand this.

see also: http://en.wikipedia.org/wiki/Triflic_acid

I hope this helps
Ok, however the same wikipedia page you mentioned:
http://en.wikipedia.org/wiki/Superacids

talks about an even stronger acid: Fluoroantimonic acid
http://en.wikipedia.org/wiki/Fluoroantimonic_acid.

Bienvenido in The Naked Scientists!