Talk:Acid/Archive 1

Archive 1

Older discussions

"Acids in Foods"? Some of these acids are *NOT* used in foods, so the list is misleading.

Norm

In the article it says that the word for acid comes from both "Arabic Azait meaning oil" and "the Latin acidus meaning 'sour'". I think perhaps it would be good to clarify that a bit, because at the moment it's somewhat contradictory.' it says that the generic formula for an acid is AH, but I've also seen HA. Is it worth mentioning that it can be either? Or is it only supposed to be AH?

I think it's a naming convention for some acids. For example, you usually say HCl not ClH. Then again, according to WebElements the Hill system formula is Cl1H1. Maycontainpeanuts 14:04, 12 Oct 2004 (UTC)

Correct me if I'm wrong, but I believe ${\mbox{H}}_{3}{\mbox{O}}^{+}$ is outdated like ammonium hydroxide (the hydronium ion doesn't exist) and the equation should be ${\mbox{AH}}(aq)\rightarrow {\mbox{A}}^{-}+{\mbox{H}}^{+}$ or something like that. Maycontainpeanuts 14:04, 12 Oct 2004 (UTC)

It depends on what particular theory of chemistry you happen to follow. The one you're speaking of is the Arrehnius theory, where all acids are explicitly compounds that can release a hydrogen ion. The Bronsted-Lowry Theory includes some other molecules that also exhibit acidic/basic behavior, and also explains the behavior of Arrehneius acids/bases. Example: HCl is an Arrhenius acid, $HCl\rightarrow H^{+}+Cl^{-}$ but is also adequately explained by the BLT (heehee) $HCl+H_{2}O\rightarrow H_{3}O^{+}+Cl^{-}$. However, the Arrehneius theory doesn't explain the behavior of some weak acids/basis, such as acetic acid or ammonia. Also, HA or AH doesn't matter.

That said, virtually all chemistry textbooks I have seen (and I mean well over two dozen) give the generic formulas as HA (or HX in the case of HCl, HI, etc.). So I would strongly recommend switching it around. stismail

I agree with you, so I took the liberty of switching this round. I also changed - to −, and → to ⇌ for these equilibria. Nearly all browsers now render these symbols correctly, and better a ? than an incorrect symbol. The whole article could do with a rewrite, IMHO, but I don't have time to do it myself at present. Walkerma 16:03, 30 August 2005 (UTC)

Suggest 4 possible wiki links and 1 possible backlink for Acid.

An automated Wikipedia link suggester has some possible wiki link suggestions for the Acid article:

• Can link tomato sauce: ...or '''[[ethanoic acid]]''': (E260) found in [[vinegar]] and tomato sauce... (link to section)
• Can link oxidation state: ...ifferent from redox reactions in that there is no change in oxidation state.... (link to section)
• Can link organic acid: ... and the acidity of the proton-donating-compound, called an organic acid, is determined by its stability when it donates protons to ... (link to section)
• Can link crude oil: ...ub> is the amount of [[titration|titrant]] (ml) consumed by crude oil sample and 1ml [[spiking]] solution at the equivalent point... (link to section)

Additionally, there are some other articles which may be able to linked to this one (also known as "backlinks"):

• In Henri Braconnot, can backlink acid properties: ... by Fourcroy (1806). Unfortunately, he did not observed its acid properties which led [[Chevreul]] to discover in 1820 [[stearic acid]]...

Notes: The article text has not been changed in any way; Some of these suggestions may be wrong, some may be right.
Feedback: I like it, I hate it, Please don't link to — LinkBot 11:30, 1 Dec 2004 (UTC)

I went ahead & added the one for oxidation state because it seemed relevant and worth adding. The others I did not add as they didn't seem as pertinent to the chemistry conversation. --Dawn Burn 04:33, 19 June 2006 (UTC)

Chloric Acid

Under Strong Inorganic Acids, Chloric acid is mentioned. But when I clicked on Chloric acid's article, it states that Chloric acid is a weak acid.

What is it, strong or weak?

It depends on your definition, actually. The most fundamental and logical definition of "strong acid" is "an acid which, in aqueous solution, is a better proton (H⁺) donor than the hydronium ion". Because the Ka of hydronium is equal to the molarity of pure water (about 55), this definition requires an acid to have a Ka of over 55 to qualify as strong. Because the Ka of chloric acid is about 10, it is a weak acid by this definition.

On the contrary, many chemists treat it as a strong acid because, in all but the most concentrated aqueous solutions, the majority of its molecules are dissociated. User: Nightvid

Reprise 2009

Several years later, this article now claims that chloric acid is weak, and the article on chloric acid now claims that it is strong! As noted above, the definitions of strong and weak acids vary, but chloric acid is only slightly weaker than nitric acid (Ka = 25, pKa = -1.4) which almost everyone classifies as strong.

I suggest removing the simplistic idea of a rigid line between strong and weak acids, and using words such as "fairly strong" to describe both chloric and nitric acids. Dirac66 (talk) 02:35, 30 April 2009 (UTC)

I think the "six acid commonly considered strong" paragraph is is fine, because that's what they are, considered. As for the paragraph that compares the strength of HClO4 to HClO we can easily be specific and use the actual pKa values. --Cubbi (talk) 02:02, 1 May 2009 (UTC)

For the six acids, I prefer Vuo's recent edit which labels them as merely examples of strong acids without saying that all others are weak. Especially since the next few paragraphs mention other examples of strong acids - sulfonic acids and superacids.

And for the series HClO4 to HClO, I have taken your advice and rewritten the paragraph with the pKa values from a textbook. Dirac66 (talk) 03:05, 4 May 2009 (UTC)

Acids in food

I think that for the "Acids in food" section, folks here need to decide whether or not they want to have fatty acids included. These types of "acids" aren't generally thought of as acids because in the forms we generally find them - with glycerols attached - they don't disolve in water, have much of a Ph, etc. But I saw that stearic acid was included on that list. For consistency sake, it should either be removed, or the other common fatty acids, such as oleic and linoleic, should be added. Maybe a separate list? I dunno...

There actually doesn't seem to be any discussion of fatty acids at all in the article, which I find a little odd, as they are one of the more notable oddities in the world of acids - with oils and fats paradoxically being made of acids and yet having a neutral Ph. --Blackcats 06:58, 15 Apr 2005 (UTC)

"Acids and Bases" template has foreign language entries

Why does the {{Acids and Bases}} template in this English Wikipedia have some entries in it written in a foreign language resulting in red links? Looks like German to me. It was not always this way; somebody changed it, but I don't know where this template can be edited to change it back. To the right here is what the display of the template looks like in this article and several others related to acids and bases. I think it should be changed back to the English language restoring the links. H Padleckas 13:08, 6 August 2005 (UTC)

I fixed this problem by editing the template back to English.
H Padleckas 08:22, 9 August 2005 (UTC)

able to give up a proton (H+ ion) to a base

I think this phrase in the first paragraph could do with being expanded a little. What does "able to give up" mean exactly? --Rebroad 07:36, 13 August 2005 (UTC)

It can release a proton and donate it to a base to form the acid's conjugate base and the base's conjugate acid. --Chemicalinterest (talk) 13:59, 18 May 2010 (UTC)

What Makes an Acid Acidic

A Question:

What makes an acid "acidic." More specifically, what about the free floating protons that makes an acid behave the way it does? What about the chemical characteristics of an acid that makes an acid "burn" through certain objects (e.g. clothes), but unaffect others (e.g. glass)?

Just Curious

So, regarding this. What those free floating protons do is react with things that can accept positive charges or have localized excess negative charges. The reason it'll burn through things like clothes is because of the structure of the chemicals that make clothes, whereas glass isn't reactive in the same way. As far as inserting this in the article, perhaps it could be put under reactivity? It really doesn't seem to be address specifically anywhere I could think of looking (Acid, proton etc) EagleFalconn 05:07, 22 January 2006 (UTC)

Kuestion - H2SO4 is a liquid in room temperature, right? If it is, then if there's a solution with 100% H and SO4 ions, would it still be an acid? Eg would it still burn through stuff? or do you need H20 (water) in the solution to make it an acid?--Number 8 00:49, 23 January 2006 (UTC)

Err, no. At room temp, H2SO4 just sitting out is a solid. If it were a liquid, if you were to heat it for example, it would still still be just H2SO4. 'cept it would be a liquid. H2O or some other polar solvent is required to turn it into sulfuric acid.EagleFalconn

H₂SO₄ is a weak acid when at 98% concentration because most of the molecules are not ionized to H⁺ and SO₄^2- ions. It's powerful properties result from it's strong attraction for water. It will take water out of any compound (e.g. sugar) that has a hydrogen to oxygen ratio of 2:1, like water, charring it. The protons have certain characteristics as oxidizing agents. They also initiate acid catalyzed protein hydrolysis on skin, making it burn. The concentrated sulfuric acid dehydrates and burns skin. Glass doesn't react with acid because the silicates are not reactive toward acids in the form that they are in. Sulfuric acid burns away things even when it isn't dissociated. --Chemicalinterest (talk) 14:04, 18 May 2010 (UTC)

acid number

I moved the acid number, which seemed specialized, to that article. Olin 23:39, 18 February 2006 (UTC)

move stuff to acid dissociation constant

Some of the material here should probably be moved to acid dissociation constant. The text here is almost longer than that article! Olin 23:43, 18 February 2006 (UTC)

strong acids merger

About 95% of the material in strong acids is already here, hence the feelers on the merger. Olin 22:13, 2 March 2006 (UTC)

Polyprotic Acids are not all Strong acids (eg. OP(OH)3)

• Holding to the belief that strong acids are essentially a subset of acids in general and limited down to only 6 or 7 acids anyway, I see no reason there needs to be a seperate article. The difference between weak and strong is the amount of ionization that occurs. However if the concern of SuperAcids is addressed, they are more complicated compounds that derive from salts of acids and other lewis acids, hence the need for superacids to have a seperate page. Das_Nerd posting from 205.160.180.4 22:07, 20 April 2006 (UTC)

Intro seems majorly incorrect

It says "An acid (often represented by the generic formula HA) is a water-soluble, sour-tasting chemical compound that when dissolved in water, gives a solution with a pH of less than 7", but that's a highly Arrhenius-centric description and is explicitly contradicted by the "Definitions" section. Water-solubility is certainly not a requirement: many carboxylic acids are sparingly soluble at best). And lowering of pH only applies to certain definitions of acidity (aqueous ammonia is basic but NH₃ is a fine Brønsted-Lowry acid in the presence of a strong enough base).

The definitions section seems to do an adequate job of introducing that there are different ways of thinking about this whole issue. Scrap the intro sentence altogether? DMacks 19:21, 6 March 2006 (UTC)

In reality you're right, although in many ways I'd prefer to keep it the way it is (which is contradictory, I know!). I think to the average laymen, this page (and a lot of chemistry pages) are too complicated, whereas that one sentence is easy to latch on to, and for that person, his/her average encounter with an acid would be such compound. On the other hand, if you deleted it, I definitely wouldn't be put up a fuss. I think there should be some generic paragraph at the beginning to keep with Wiki standards. I did a lot of editing on this article a few weeks ago, and I appreciate your comments. Olin 19:40, 6 March 2006 (UTC)

I rewrote this, trying to keep the simplicity while keeping it correct. Is it better now? Walkerma 19:59, 6 March 2006 (UTC)

I just hacked on it a bit more. Separated the idea of acidity (lower pH) from an effect of that (sour taste) that many consider a hallmark of acids. DMacks 20:10, 6 March 2006 (UTC)

"Acids generally taste sour; however, tasting acids, particularly concentrated acids, can be dangerous and is not recommended." Why is an encyclopedia making recommendations at all, let alone such a manifestly ridiculous one as this? "is not recommended" by whom? does this mean I should stop eating citris?

Hacked this out for now. It seemed quite misplaced (and badly written) for the intro. Perhaps some note of common acids in foodstuffs within the main article would be better? (Or have I just missed this?) --Plumbago 16:16, 23 September 2006 (UTC)

Another comment: better intro than Ph scale

I've got another comment on the intro: Isn't there a better way to define an acid, in layman's terms, but refer to it's actual physical characteristics rather than how it rates on the Ph scale? To me it's like defining a bird by its poop rather than some genetic sequence. Am I way off base here? Speaking of which, check out Base (chemistry)'s intro. It seems to stays simple, provides alternative definitions, and doesn't get complex, not like the article for electron. I really like the idea of keeping the intro simple and easy to read, but we should hold ourselves to a standard that is equal to what a technical, professional definition would be. Rhetth 00:14, 6 August 2007 (UTC)

Inorganic acids

I think it would be a good idea for someone to create INORGANIC ACIDS article. Wikipedia HAS the article about the organic ones but not about inorganic...

-I added this subject to the requests, i think "Inorganic Acids" can also be merged with the "Acid" article when it has been created user:Kiptrev

Solution

All the acid data here is based on water solutions, but couldnt we add how to turn acids constants and data from normal water solution to anyother solution? Like if you have liquid ammonia solution water is the acid and other weaker bases becomes acids and such

The water soluble definition generally meets the criteria for commmon acids. They dissociate to form protons and anionic complexes, their strength determined by the level of the dissociation. Few acids aren't water soluble, and they are defined by the Bronsted-Lowry Theory. It states that acids donate protons (the same thing as an H⁺ ion) to bases, and bases accept them. So ammonia is a base if it accepts an H⁺ to form NH₄⁺ ions. It is an acid if it donates a proton to form the amine complex, which is an NH₂⁻ ion. --Chemicalinterest (talk) 14:11, 18 May 2010 (UTC)

In aqueous solution ammonia acts as a base and its acidity is negligible. However one can also have liquid ammonia with no water present, in which case one NH₃ molecule can act as a base and one as an acid: 2 NH₃ → NH₄⁺ + NH₂^-. The point of the original comment is that this article needs on acidity and basicity in nonaqueous solvents, even if the acids and bases considered are also soluble in water. Dirac66 (talk) 15:21, 18 May 2010 (UTC)

Its caracteristics

shouldnt there be a section for the caracteristics of an acid and a base? paat 21:01, 17 June 2006 (UTC)

In the introduction there is. --Chemicalinterest (talk) 14:19, 18 May 2010 (UTC)

Constants

I think we should add how to calculate the acid/base constant for the acid/base, not its conjugate only

pH

Why p is small letter and H is capital letter

The "p" means "base-10 log", and I think is always loewr-case in that meaning. Why? Dunno...why not? The thing we're calculating the log of is hydrogen concentration: "H" is the chemical symbol for hydrogen, and is capitalized because chemical symbols always are. By the same pattern, it's common in medicine to talk about pO₂ and pCO₂. DMacks 17:18, 19 July 2006 (UTC)

Common household liquids, ranked by acidity

I think the article could use a list of commonly consumed liquids, ranked by acidity. Acidity is something we can directly experience by taste. Could just list it like Lemon Juice, Coffee, Coca Cola, Water, Milk, Mylanta (assuming I got the order right. Mathiastck 17:25, 17 August 2006 (UTC)

vandalism?

uhm, anyone else notice the "cock nose" acids and bases? i dont think that should be there.... —The preceding unsigned comment was added by Mad Gouki (talk • contribs) 20:36, 28 January 2007 (UTC).

nucleic acid

where does Nucleic acid fit into the discussion? 131.111.8.102 23:23, 13 February 2007 (UTC)

A nucleic acid is a type of organic acid. The phosphate group is a derivative of phosphoric acid. DMacks 23:32, 13 February 2007 (UTC)

Lewis Acids

Shouldn't there be a section in this article indicating that not all acids have to include a proton?

Is the mention in the definitions section enough? Cubbi 16:16, 4 April 2007 (UTC)

vandalism

"homo,homosexual", don't know what the Lewis terms were

TDupont 19:29, 24 March 2007 (UTC)

Arsenal rock An acid? in first line?... ...i wounder...:? —Preceding unsigned comment added by 85.246.81.116 (talk) 10:50, 18 April 2009 (UTC)

rust acid

apparently the opposite of regular rust is rust acid, any1 know the properties of this acid?

Never heard of it. --Chemicalinterest (talk) 14:19, 18 May 2010 (UTC)

New Section for Factors Affecting Acidity?

Should there be a section for factors affecting acidity

For example, electronegativity/induction, resonance, bond strengths, electrostatic/field effects, hybridization, aromaticity, solvation....? —Preceding unsigned comment added by Fantaseedude (talk • contribs) 18:10, 28 October 2007 (UTC)

Polyprotic acids

Do polyprotic acids not deserve their own separate article? Monoprotic acids get their own artcle so why not polyprotic? The properties of some polyprotic acids (such as Phosphoric Acid) are very different to those of monoprotic acids and so simply grouping them with "acids" doesn't make much sense. TheTrojanHought 14:12, 13 November 2007 (UTC)

Common acids

Citric acid is a carboxylic acid. —Preceding unsigned comment added by 86.152.97.42 (talk) 14:38, 4 March 2008 (UTC)

Merge Monoprotic Acids

Due to the lack of content on the subject, I am suggesting to merge any extra information available on Monoprotic acids into the current article as a new subsection before Polyprotic Acids.Aly89 (talk) 21:44, 28 May 2008 (UTC)

There is now an article named Monoprotic acid (without the s), but it is too short to be of much value. I would favour merging that article into this one as a subsection (with the title changed to the plural), located before Polyprotic acids as you suggest. Dirac66 (talk) 02:36, 29 May 2008 (UTC)

Sorry, I meant Monoprotic Acid, but unfortunately typed it out with an extra 's'. I am kindof new to Wikipedia, so if anyone would love to take a shot at it, be my guest! Aly89 (talk) 02:45, 29 May 2008 (UTC)

Ok. I have successfully merged the Monoprotic Acid article into Acids article. If anyone has any problems or any concerns, drop me a message. Feel free to cleanup if I made any grammatical or factual error in my merger. Aly89 (talk) 23:59, 1 June 2008 (UTC)

Solid?

Can an acid be a solid at room temperature? As an example, salt and vinegar-flavored potato chips use distilled white vinegar that has been evaporated into a powder. But neither the acid article nor the acetic acid article mention that an acid can be a powder at room temperature. Can we get some clarification about this ab toh articles? Badagnani (talk) 02:56, 9 July 2008 (UTC)

BTW, I heard that they use a sodium hydrogen acetate salt, which is a mixture of sodium acetate and acetic acid. --Chemicalinterest (talk) 14:23, 18 May 2010 (UTC)

huh? There are probably hundreds of thousands of acids that are solid at room temperature. This article doesn't mention it because there is no connection between phase state at room temperature and acidity. It would be like saying "an acid can be colorless at room temperature". Makes no sense to me. --Cubbi (talk) 03:36, 9 July 2008 (UTC)

I could not find anything in the article that gave the possibility that an acid could be a solid (except when frozen). However, the example of dehydrated vinegar I gave would be such an example. So, the article should make it clear that acids are not always liquids. Badagnani (talk) 03:55, 9 July 2008 (UTC)

Er, anything is only ever a solid when it's frozen. Every chemical has its own melting point, so it's just that some common acids people encounter happen to be liquids at room temperature. The melting point of acetic acid is somewhat below room temperature, so the "dehydrated vinegar powder" is clearly not actually that chemical. Check the ingredients...I think "salt & vinegar" chips are coated in a combination of sodium acetate and lactic acid. No vinegar there at all (!), but two solids (one of which is an acid). The chemical combination "sodium acetate + lactic acid" in your mouth is equivalent to "acetic acid + sodium + lactate", and therefore tastes like vinegar and salt were actually used in the coating. DMacks (talk) 04:06, 9 July 2008 (UTC)

Please do not cross-post your questions. Thanks, Cacycle (talk) 04:13, 9 July 2008 (UTC)

The reason for cross-posting is that in many cases the question will go unanswered at one page, while be answered at the other (due to disinterest or failure of any editors to notice it). Whatever the case, I will do so if I feel it is appropriate.

The ingredients list dehydrated distilled white vinegar, just as I had mentioned earlier.

Badagnani (talk) 04:46, 9 July 2008 (UTC)

Your chips contain either "dehydrated distilled white vinegar", which would be more or less pure liquid acetic acid, and/or they contain the leftovers from from distilling off water and acetic acid from vinegar, which would be a smelly powder. Both things are NOT the same. Did you google for this and read our articles? Cacycle (talk) 12:57, 10 July 2008 (UTC)

Yes, of course. The articles state that acids may be solid if frozen, but do not give the possibility that they may be in powdered form at room temperature. If dehydrated (i.e., without water), I don't believe it could be "more or less pure liquid acetic acid." The chips are crisp and have no detectable fluid but are extremely sour. Badagnani (talk) 12:59, 10 July 2008 (UTC)

BTW, you can also buy acetic acid adsorbed on maltodextrin, which gives a powder. I suggest that you carefully read and try to understand the answers you got above and on Talk:Acetic acid and then do your own homework on Wikipedia and Google if still necessary. Cacycle (talk) 13:18, 10 July 2008 (UTC)

Let's try to be congenial and collegial, would that be all right? (That is part of the Wikipedian ethos). The ingredients also mention maltodextrin. So, to get the Acid article complete, it still states that acids may only be solid if in frozen form. However, we have now a solid powdered adsorbed form of an acid in maltodextrin. Is this reality reflected in the Acid article? Badagnani (talk) 13:28, 10 July 2008 (UTC)

Perhaps we do need to be more patient with this question. As a chemistry professor I have found that if one student asks a question, there are usually others who are confused about the same question. Badagnani was uncertain about the possibility of solid acids, so I suggest adding a brief clear answer such as "Acids can occur in solid, liquid or gaseous form". This would serve to dispel any idea that acids must be liquids in bottles. We could also add that they can be either pure or in solution, which again may not be obvious to everyone. Dirac66 (talk) 14:05, 10 July 2008 (UTC)

That is exactly the conception most people have: that acids are always liquids in bottles. Badagnani (talk) 14:24, 10 July 2008 (UTC)

Pure acetic acid is always a liquid at room temperature...that's something that is intrinsic to that compound. However, a liquid adsorbed onto a solid (or powder) may appear as an overall solid. A liquid could soak into a solid: a wet sponge is still a solid sponge and the water in it is still a liquid. Or one could disperse a small amount of moisture onto a large amount of solid: a few drops of water well mixed into a bucket of sand doesn't look "wet". DMacks (talk)

"Pure acetic acid is always a liquid at room temperature." True, but we can obtain a solid by change of acid or of temperature. (Or even by waiting until the rising price of oil forces us all to re-define "room temperature" as 15 C, since acetic acid freezes at 16.6 C !)

Anyway, I have now made the following one-line addition at the end of the Properties section:

"Acids can occur in solid, liquid or gaseous form, depending on the temperature. They can exist as pure substances or in solution."

I believe this is a simple and clear answer for readers who are honestly unsure of whether acids are confined to the liquid state. Dirac66 (talk) 17:11, 10 July 2008 (UTC)

The recent addition to the article has turned out to be "Acids can occur in solid, liquid or gaseous form, depending on the temperature and specific properties of the chemical being examined. They can exist as pure substances or in solution". While I might not agree with explicitly writing that acids can occur in any state, but have been forced to reconsider after reading this discussion; I do disagree with "They can exist as pure substances or in solution". Add additional chemicals, even Sodium Chloride for example, can make it "impure". With its current state, it sounds as if acids have a special property of only being pure and and aqueous. I propose to either clarify this point by expanding on it, or remove it. In case of me being wrong - since I am no masters or bachelor in Chemistry, please correct me. I will also make further modifications to the state part of the addition to explicitly point it to "Melting Point" and "Boiling Point" for further clarification. Aly89 (talk) 19:41, 11 July 2008 (UTC)

Properties

when it said when acids react with metal carbonates it produces water, co2 and salt i would like to know that salt means NaCl. It could mislead some individuals as to me salt could mean other salts eg. LiCl —Preceding unsigned comment added by 121.72.133.104 (talk) 04:14, 22 March 2009 (UTC)

The article says *a* salt. Which salt depends on which acid and which carbonate. NaCl is formed from HCl and Na₂CO₃, but LiCl is formed from HCl and Li₂CO₃. Dirac66 (talk) 16:06, 22 March 2009 (UTC)

Electron movement arrows in Lewis acid-base reactions

I see that electron movement arrows have now been added to the diagrams showing simple Lewis acid-base reactions. This is a very good idea, but the arrows have to be placed a little more carefully. In the current version for the BF₃ + F^- reaction, the arrow appears to be an attack of the F nucleus on the B-F bond. It should be moved a little to the left to show an attack of an F lone pair on the B nucleus. Also for the NH₃ + H⁺ reaction, the arrow starts at the N nucleus, but should start at the N lone pair. Dirac66 (talk) 13:43, 30 April 2009 (UTC)

Done Myceteae (talk) 08:48, 3 May 2009 (UTC)

That's right. Thank you. Dirac66 (talk) 15:12, 3 May 2009 (UTC)

"Six strong acids"

Should there be a discussion of the "six strong acids" commonly listed in general chemistry books and introductory materials (these being HCl, HBr, HI, HClO₄, HNO₃ and H₂SO₄)? Many sources say that these are the strong acids and all other acids are weak. Since many of the people reading this article are likely to be students, perhaps a brief mention of this common list, and why it is not strictly correct, is appropriate. On the other hand, it may just be unnecessary detail. Any thoughts? Myceteae (talk) 02:55, 28 July 2009 (UTC)

We've got a whole Strong acid article, which is linked from the navbar. On the article here, the Acid#Acid strength section does a pretty good overview (including listing the Big 6 and linking the Strong acid page). DMacks (talk) 03:23, 28 July 2009 (UTC)

It lists them as examples of strong acids, and several of them are used to illustrate various properties throughout the article, but I was wondering whether it would be worthwhile to state explicitly that these six are commonly listed in textbooks as the six strong acids, and that this convention is simply a convenient oversimplification. But it is probably not terribly useful to add this discussion.Myceteae (talk) 04:29, 28 July 2009 (UTC)

Do leading recent textbooks really say that "all other acids are weak"? I just checked General Chemistry by Petrucci, Harwood and Herring (8th ed 2002, p.147 and p.675) which just lists "six common strong acids"; this does not imply the non-existence of other strong acids. If there is no widespread error, why correct it, especially since the article explicitly mentions some less common strong acids? Dirac66 (talk) 20:42, 28 July 2009 (UTC)

I went back to my gen chem text and it was not stated as strongly as I remembered. On chemistry.about.com's acid strength page does repeat this fallacy, however, and in hunting around the web I have seen other examples. Ultimately I do not think it needs to be addressed beyond what is presented in the current discussion, although it is something to keep in mind for future edits. Myceteae (talk) 22:50, 8 August 2009 (UTC)

The neutrality of this article is disputed - where/why?

Any idea why this sign is on the article? It was introduced here with no explanation by an IP-user a few days ago (5. march). -- Christian75 11:19, 8 March 2010 (UTC) —Preceding unsigned comment added by Christian75 (talk • contribs)

Yes, and this IP user's only other edit was one minute later when s/he placed the same notice on the Alkali article. I think these two edits were meant as a joke - if it's only acid or only alkali it's not neutral :-)) Very funny but I will now remove the notice from both articles. Dirac66 (talk) 14:54, 8 March 2010 (UTC)

acid

how is acid so vital and yet we/us as the student/kids have to use it and be exposed to so much harm? —Preceding unsigned comment added by Lilbluewave (talk • contribs) 02:48, 9 April 2010 (UTC)

I'm not sure that makes any sense. Some things that are important can be dangerous. Actually, almost everything can be dangerous. Some things are dangerous in their raw industrial form but usually safer or more processed by the time consumers get them. In school, you learn how things work and are made, not just how to buy finished products, so you naturally have to work with some of those not-very-friendly starting materials My students actually think it's neat that they can take something that has so many warning labels on it and make something that might be both very important and very mild. DMacks (talk) 13:46, 9 April 2010 (UTC)

It is not that harmful. Only a few acids, like HF, are harmful when dilute. More are harmful when concentrated. --Chemicalinterest (talk) 14:25, 18 May 2010 (UTC)

What does "it" mean here? "Acid" is not a single substance, but a (large) class of substances. As stated, SOME acids are harmful, and the danger of any one may depend on concentration as well as many other factors. Dirac66 (talk) 15:27, 18 May 2010 (UTC)

Common Properties

On the Wikipage for Alkali, there is a section on "Common Properties," which list various properties common of a base, such as "Concentrated solutions are caustic (causing chemical burns)." Why does the acid page not have such a section appropriate to acids?
Christopher, Salem, OR (talk) 12:18, 17 June 2010 (UTC)

Biological occurrence

Does anyone have any suggestions for improving the section on biological occurrences? I think the discussion should focus on the significance of the acidic character of various biomolecules and drugs, and discuss how their acidity affects (or determines) their biological properties, without dwelling on the biological properties themselves. I think some mention of their biological role is warranted, but with a focus on their chemistry, and links to appropriate articles for more background. For example I've just added an explanation of what makes nucleic acids acidic (the phosphate group). Prior to that the discussion of nucleic acids focused on their role in the genetic code, which is interesting, but failed to relate back to the main topic of this article. Overall, I think the entire section could use better organization and more focus. What do people think?

I was also thinking about adding some info about acid-base catalysis in biochemistry to this section, but realized that the topic of acid catalysis in general is largely missing from this article. I decided to add a new heading about this topic to the talk page (see Talk:Acid#Acid_catalysis below), since the topic deserves attention outside of the biological occurrences section, and people not (otherwise) interested in the role of acids in biology might want to contribute to expanded coverage of acid catalysis. Whether or not we add more info about acid catalysis elsewhere in the article, I would be interested in at least briefly covering it in the biological occurrences section. I would link to the main article on acid catalysis, although this article does not discuss enzymatic catalysis. 24.17.176.10 (talk) 06:19, 13 August 2010 (UTC)
The above paragraphs were written by me. I thought I was logged in, oops. Myceteae (talk) 06:20, 13 August 2010 (UTC)

Acid catalysis

Does anyone else think that this article should include at least some additional information on acid catalysis? I didn't re-read the entire article, but a text search of the page for catalys turns up only one mention, in the applications of acids section: Acids are used as catalysts; for example, sulfuric acid is used in very large quantities in the alkylation process to produce gasoline. Strong acids, such as sulfuric, phosphoric and hydrochloric acids also effect dehydration and condensation reactions. I was actually thinking about adding a discussion of general acid-base catalysis, or perhaps just acid catalysis, by enzymes to the biological occurrences section when I decided to see if the topic was discussed more generally elsewhere in the article. I would be happy to add some general information, but I'm far from being an expert in the field and would have to rely heavily on my organic chemistry and biochemistry textbooks. Do people agree that the discussion of acid catalysis ought to be expanded, and if so does it deserve its own section or could it be inserted into one of the existing sections? Would anyone be willing to help write such a section, or discuss some ideas and provide guidance if I decide to take this on? Myceteae (talk) 06:30, 13 August 2010 (UTC)

As you have noticed, there is already an article on acid catalysis, which can of course be expanded further. I don't think that detailed discussion of catalytic mechanisms belongs in this article on acids, but I think the brief mention you found could be expanded slightly to mention organic and biochemistry, and include a link to the acid catalysis article. (The current link is only to catalysis rather than acid catalysis.)

Also the mention could be a separate subsection so that it appears in the table of contents. Perhaps a subsection (of Applications) labelled Acid catalysis with a line saying See main article: Acid catalysis, and beginning with "Acids are used as catalysts in industrial and organic chemistry and in biochemistry; for example, sulfuric acid ..." Dirac66 (talk) 13:02, 13 August 2010 (UTC)

Thanks, Dirac, for the input. I've added the subsection with some modifications from your suggestion. When I get home I can add a reference to Voet & Voet's Biochemistry for enzymatic acid catalysis, and I'll see if I can't dig up references for industrial & organic chemistry. The application section, as a whole, lacks references, and I suspect that much of the content can find support in a gen chem book, so I will see what I can do about that. I decided to be bold and commit the edit, but I am wondering how much—if any—additional discussion is warranted. You're absoltuely right that a discussion of reaction mechanisms involving acid catalysis is beyond the scope of this this article, but it seems like some additional info and/or links could be useful. I also wasn't sure when to link to other articles. The original line linked to the article on sulfuric acid, but not to phosphoric or hydrochloric acids. All three of these acids are mentioned and linked to throughout the article so I'm not sure that links to any of these articles are necessary in this subsection; on the other hand, I see no reason to link to an article on one acid and not the other two. I decided that not editing these links would be more prudent given my uncertainty, and so I've left the link to sulfuric acid in place without adding the other two. The original also linked to catalysts and alkylation, which seems appropriate, and I added links to enzyme, dehydration reaction and condensation reaction, three other terms which may be unfamiliar to readers. I considered adding links to industrial chemistry (note that this redirects to chemical industry), organic chemistry and biochemistry but decided these were not absolutely necessary and wanted to avoid over-linking. The use of links is inconsistent throughout the entire article. Should every single acid w/ a corresponding article get a link when it is first mentioned? When is it appropriate to add a link after the first appearance in the article? For example if an acid is mentioned in a section that a reader might jump to without reading the proceeding the proceeding discussion, do we link to the article on that acid? --MYCETEAE - talk 03:29, 16 August 2010 (UTC)

Looks OK - I think the link to Acid catalysis is the important one as it may not occur to readers that this article exists. For a specific substance such as phosphoric acid, a curious reader would probably think to search for that term. And yes, the use of links is inconsistent, because the article has been written by many people. It is probably not worth the time which would be required to impose consistency on the whole article. Dirac66 (talk) 12:00, 16 August 2010 (UTC)

Removed Common usage section

I removed the Common usage section. It does not add to the discussion; also, it does not cite any sources and looks like original research. A discussion of the nature of burns from an acid and the difference between acid strength and corrosiveness might be appropriate, but I don't think the unverified assertion that people "typically" have an erroneous concept of what constitutes an acid has any place here. MYCETEAE - talk 21:18, 13 September 2010 (UTC)

I agree completely. Also I don't think Wikipedia should suggest that it is acceptable (even in supposed common usage) to refer to bases as acids. And the words "even though the liquid is acquiring a positive charge, not negative as with real acid." are quite incorrect. Dirac66 (talk) 01:18, 14 September 2010 (UTC)

If someone can show that such usage is indeed common, I think it is worth a mention, as long as it is made clear that this folk definition is incorrect. The discussion, if someone wants to replace it, probably does not need its own section and deserves at most a brief mention in the intro, or perhaps as part of a section on acid burns or corrosion vs. acidity. We certainly don't want to introduce any new erroneous concepts while trying to dispell another, as with the statement about the liquid acquiring a positive charge. MYCETEAE - talk 05:09, 14 September 2010 (UTC)

Changes to the introduction

The introduction says that an acid is a substance which "tastes sour, reacts with metals and carbonates, turns blue litmus paper red..." I would argue that these are the properties of an acid, and that only the last part of the sentence "...and has a pH less than 7.0 in its standard state" is the definition of an acid. Also, the sentence "Acid/base reactions differ from redox reactions in that there is no change in oxidation state" seems a little out of place for the introduction. Finally, my understanding of chemistry is not very strong, but I have been taught that acids are only classified as such if they are in solution, but the introduction says that acids can be pure substances, and can be gases or solids. The Hydrochloric acid page specifies in the first sentence that, to be classified as hydrochloric acid, the hydrogen chloride must be in solution. Is this not the case with all acids? —Preceding unsigned comment added by 70.27.193.8 (talk) 21:15, 31 October 2010 (UTC)

I have also wondered about this, and think it would be great if the article could provide some clarification, or if someone could at least expand on that here. I most often see this distinction made with HCl; in fact, I'm not sure if I've ever seen it with other acids. Is the distinction between hydrogen chloride and hydrochloric acid nothing more than a linguistic cue that chemists sometimes use to specify whether they're talking about the covalently bonded molecule or the fully dissociated H₃O⁺ and Cl^- ions? Or is the satement from the hydrochloric acid article correct, and if so, shouldn't this be addressed in the article? Also, the section on Brønsted acids uses HCl to show that acid-base reactions can occur in non-aqueous media. I actually added this section to the article, and I adapted it from my general chemistry textbook. This seems to contradict statement from the hydrochloric acid article. --MYCETEAE - talk 05:38, 2 November 2010 (UTC)

The traditional definition of acid is that its pH is less than 7 in an aqueous medium. But these days, the acidity concept has been extended to non-aqueous solvents (in particular, consistent scales in DMSO have been developed), highly acidic or basic media (for example, the Hammett acidity scale for acidity in concentrated sulfuric acid), and even the gas phase (usually via mass spectrometry). There is also the idea that the acid will heterolytically dissociate (not homolytically, which would make radicals) to give a conjugate base. According to the IUPAC gold book, an acid is:

"A molecular entity or chemical species capable of donating a hydron (proton) (see Brønsted acid) or capable of forming a covalent bond with an electron pair (see Lewis acid)."

Does this help? Eugene Kwan (talk) 10:14, 3 November 2010 (UTC)

There may also be an issue with the discussion of substituted carboxylic acids. See page 13 on at http://isites.harvard.edu/fs/docs/icb.topic776365.files/lecture%2017.pdf. Eugene Kwan (talk) 10:18, 3 November 2010 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Acid/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Can I please request that the strength of acids relative to each other be mentioned, in a way that there pH at 1M or another value of concentration is kept the same. This way students can compare their strengths using pH facts. Also, each individual Acid should mention at least once its pH at a concentration. At the moment, few acids even mention pH in their article and this is something that is lacking. Thanks stags 08:41, 14 October 2008 (UTC)

Last edited at 08:41, 14 October 2008 (UTC). Substituted at 14:08, 1 May 2016 (UTC)