The Naked Scientists

The Naked Scientists Forum

Author Topic: The strongest acid...  (Read 63632 times)

Offline bostjan

  • Sr. Member
  • ****
  • Posts: 107
    • View Profile
Re: The strongest acid...
« Reply #50 on: 31/08/2006 05:40:15 »
ahh, i see.  very good response.
 

Offline dtx

  • First timers
  • *
  • Posts: 3
    • View Profile
Re: The strongest acid...
« Reply #51 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.
 

Offline Mr Andrew

  • Sr. Member
  • ****
  • Posts: 206
  • God was primitive man's attempt at Physics.
    • View Profile
Re: The strongest acid...
« Reply #52 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
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: The strongest acid...
« Reply #53 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.
« Last Edit: 07/11/2007 16:29:31 by lightarrow »
 

Offline Heliotrope

  • Sr. Member
  • ****
  • Posts: 151
    • View Profile
    • http://www.davethedrummer.com
Re: The strongest acid...
« Reply #54 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.
 

Offline Heliotrope

  • Sr. Member
  • ****
  • Posts: 151
    • View Profile
    • http://www.davethedrummer.com
Re: The strongest acid...
« Reply #55 on: 12/11/2006 19:01:56 »
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: The strongest acid...
« Reply #56 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.
 

Offline Heliotrope

  • Sr. Member
  • ****
  • Posts: 151
    • View Profile
    • http://www.davethedrummer.com
Re: The strongest acid...
« Reply #57 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.
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: The strongest acid...
« Reply #58 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.


« Last Edit: 18/11/2006 14:19:11 by lightarrow »
 

Offline Heliotrope

  • Sr. Member
  • ****
  • Posts: 151
    • View Profile
    • http://www.davethedrummer.com
Re: The strongest acid...
« Reply #59 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.

 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: The strongest acid...
« Reply #60 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).
 

Offline Heliotrope

  • Sr. Member
  • ****
  • Posts: 151
    • View Profile
    • http://www.davethedrummer.com
Re: The strongest acid...
« Reply #61 on: 17/11/2006 21:16:44 »
Gotcha.
Thanks.
:)
 

Offline Mr Andrew

  • Sr. Member
  • ****
  • Posts: 206
  • God was primitive man's attempt at Physics.
    • View Profile
Re: The strongest acid...
« Reply #62 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?
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: The strongest acid...
« Reply #63 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.
 

Offline Weldmann

  • First timers
  • *
  • Posts: 5
    • View Profile
The strongest acid...
« Reply #64 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?
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
The strongest acid...
« Reply #65 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).
« Last Edit: 13/08/2007 17:46:32 by lightarrow »
 

Offline vinuuraj

  • First timers
  • *
  • Posts: 2
  • krishnaraj(vinuuraj)
    • View Profile
The strongest acid...
« Reply #66 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.
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8670
  • Thanked: 42 times
    • View Profile
The strongest acid...
« Reply #67 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?
 

Offline Wally

  • First timers
  • *
  • Posts: 6
  • Hacia el Futuro, Hacia la Victoria Siempre
    • View Profile
    • E5
The strongest acid...
« Reply #68 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: newbielink:http://en.wikipedia.org/wiki/Superacids [nonactive]

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 newbielink:http://www.jenck.com/t-acidez.htm [nonactive]., 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: newbielink:http://en.wikipedia.org/wiki/Triflic_acid [nonactive]

I hope this helps
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
The strongest acid...
« Reply #69 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!
« Last Edit: 20/11/2007 15:27:20 by lightarrow »
 

The Naked Scientists Forum

The strongest acid...
« Reply #69 on: 20/11/2007 15:22:41 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums