Talk:PH/Archive 1

message: What is the pH of 4% Hydrochloric acid?
:I doubt Wikipedia is the right place to ask that question. You might try in the newsgroup sci.chem... -- Schnee 17:48, 21 Sep 2003 (UTC)
replies: text: It would also be more accurate to define pH in terms of hydrogen activity as opposed to hydrogen concentration, this can be a very important difference in some systems  (Seawater for example). --Piyrwq 02:15, 15 August 2005 (UTC)
thread_title:  pH 

message: Is the statement that "the only neutral substance is distilled water" correct?  If neutrality is simply pH=7, then it's trivial to create a "neutral" solution that isn't distilled water.  For example, add baking soda to water to raise the pH.  Then, add just enough vinegar to make the pH=7.  The water is neutral (pH=7), but isn't distilled, either.   Perhaps we are confusing "neutral" with "pure?"
I think this is important to clarify, especially since the article calls this out as being "important to note."
:The scale shows pure water as having a pH of 7.0.  But this cannot be correct.  Pure water contains no ions at all as the water molecules only disocciate when impurities are present.  Thus a logarithmic scale of ion concentration cannot be applied to a substance that has no ions.  Deionised water is the purest that can currently be obtained (the clue is in the name).  It is impossible to measure the pH of deionised water because the indicator itself plus its solvent introduces ions in the same quantity as water that disocciates and thus invalidates the results because all the ions are introduced by the measurement method.  Similarly, an electronic pH meter's indication is useless because the pH electrode relys for its operation on a conductive sample, something that deionised water most definitely is not.  In fact deionised wter will degrade a pH electode because it has an enormous affinity for ions and will 'suck' them out of the electrode.
...Incidentally, pure distilled water, when exposed to the atmosphere, has a pH of 5.7, due to carbon dioxide ingassing.
:But this doen't occur instantly.
:Agree on both points. Note removed. Vsmith 00:47, 27 Feb 2005 (UTC)
thread_title:  'Neutral' substance 

message: I re-jigged part of the pH definition in an effort to get away from this re-occuring idea that pH is somehow an exact number between 1 and 14.  For example, the pKw isn't even really 14, it's 13.995.  By pointing this out maybe people won't get so caught up in some of these 'laymen' definitions.  
I'm still not very happy with my wording though, and will likely reword a few things soon if someone else doesn't do it first. Piyrwq 14:47, 19 August 2005 (UTC)
thread_title:  pH Definition 

message: The statement "The p stands for the German Potenz" is a myth and should be removed.
Sorensen arbitrarily chose the letters p and q for two solutions in his paper. The term pH is derived from solution p with the unknown concentration of H+ ions. Mr. Davies class hates ph scale.
Reference:
Norby JG "The origin and the meaning of the little p in pH" Trends Biochem Sci. 2000 Jan;25(1):36-7
:pH=power of potential of hydrogen  Medscin 17:50, 2 January 2006 (UTC)
thread_title:  pH terminology 

message: :pH value has no unit.
Not strictly true: its units are log_{10} mol.dm^{-1} which is not dimensionless at all, just a very weird dimension. Very weird is not the same as none.
:pH = − log10[H + ]
I changed it to the more traditional formula, because the following text refers to that formula. If u want to add the more accurate formula, put it elsewhere and explain the difference.
--대조 | Talk 20:40, 15 January 2006 (UTC)
thread_title:  Units and formula 

message: having spent an hour trying to find this out as part of my chemistry homework, i still have absolutely no idea as to the word that the name 'pH' is derived from!!! according to my chemistry teacher it's a German word, but i am still completely clueless as to what this word is.  if  anyone knows, could they please post it, as i know you are all highly intelligent people.
Thanks--XMagicFairyX 19:25, 6 February 2006 (UTC)
replies: text: There's a bit of confusion across the web on this. The two I've seen are French and Dutch (the Dutch one might be the one you're looking for). The French one, however, is more commonly accepted (that's what my textbook says). This is a question for Wikipedia:Reference desk — Edward Z. Yang(Talk) 00:14, 7 May 2006 (UTC)
thread_title:  why 'pH scale'??? 

message: How is it edited?  Redox should not be in the box about acid-base chemistry. Olin 22:26, 19 February 2006 (UTC)
replies: text: I find that redox-ractions is somewhat related to acid-base, and thuse appropriate. So I think it should stay. --vidarlo 10:59, 6 March 2006 (UTC)
thread_title:  that box to the right 

message: Battery acid -0.5 
Does it mean that [H+] is larger than one? Or is it a mistake?
No, it's not a mistake. 10 to 0.5 is about 3.2 mol/L. Space Cadet 01:07, 28 February 2006 (UTC)
replies: text: You have to factor molecular activity. I'm not familiar enough with the mathematics/equations to give you an exact number though. — Edward Z. Yang(Talk) 02:51, 21 October 2006 (UTC)
thread_title:  negative pH

message: is negative pH possible to create in an aqueous solution.  i know it is certianly possible to have negative pH with strong acids.  but is it possible to prepare it in water if it is limited by Kw?  also, is a high pH possible to prepare (>14)?
Yes, it is possible to prepare it in water because your [OH] will be less than 10 to -14, so multiplied by each other they will give the exact Kw. As far as > 14, your everyday "Liquid Plumber" has pH of about 15. Space Cadet 12:15, 27 February 2006 (UTC)
thread_title:  negative pH in aqueous 

message: I've started cleaning up the math formulas in this article, as some of them is written in html. This defies the point of letting the user choose whatever to display as png, html or MathML. All formulas should be written in LaTeX. Further, should we use \lg{\left[H_3O^+\right]}or \log{\left[H_3O^+\right]}?--vidarlo 10:58, 6 March 2006 (UTC)
replies: text: Well, since mathematicians get all scuffly when you use log to mean base-10, I'd say \log_{10}{\mathrm{[H_3O^+]}} is our best bet. — Edward Z. Yang(Talk) 00:17, 7 May 2006 (UTC)
thread_title:  Math formulas. 

message: User:Hdante recently reverted the pH equation to this form:
:\mbox{pH} \approx -\log_{10}{\frac{[\mathrm{H^+}]}{1\, mol/L}} = -log_{10} {|[\mathrm{H^+}]|} 
I find the addition of the absolute value signs quite puzzling: isn't concentration always positive? (I suspect that I am misinterpreting the meaning of the straight bars) Furthermore, because brackets denote concentration/molarity in mol/L, wouldn't dividing by 1 mol/L make the concentration unitless? I mean, pH is a unit-less scale, but I would think it would be improper to remove the units from inside the equation...? Someone please explain this to me. — Edward Z. Yang(Talk) 15:50, 14 May 2006 (UTC)
replies: text: This is mathematical bureaucracy, required to give the complete insight of the equations. The first point is that you shouldn't take the log of a number with a unit. The second point is that the activity aH+ is unitless, so that it can't be formally compared to something that has a unit (apples X oranges). The last point is that the equation aH+ = [H+]/1molL-1 defines the scale of aH+, that is, it is unitless, but its value is numerically equal to the concentration (in whatever units you'd be using). The last equation, pH = -log |[H+]| means "when calculating the log, don't take into account the mol/L thing", ex: pH = -log |1e-7 mol/L| = -log (1e-7). A similar equation is used in the german wiki.  --Hdante 16:57, 14 May 2006 (UTC)
replies: text:  Aha! Suddenly it makes sense. Thanks for the clarification. Maybe a footnote's in order? — Edward Z. Yang(Talk) 00:21, 15 May 2006 (UTC)
replies: text: Hello. I think an example is better than a footnote. What's the pH of a lemonade ? --Hdante 19:08, 16 May 2006 (UTC)
replies: text: Depends on the lemonade. There is a list of pH for some common products, and that should do. Most people should be able to relate it to that list... But it is a logaritmic scale, so I'm not so sure anyone will understand that too easily. Maybe a simple chart with the concentration of H^+ vs. the pH would do? I'm gonna make one soonish... vidarlo 07:57, 18 May 2006 (UTC)
thread_title:  Absolute value on concentration 

message: Can someone please explain to me how one might determine the pH at which an indicator changes color?
:Your question should be directed to the reference desk in the future. However, I'll indulge you. Read pH indicator to find out more on what indicators really are, and then think logically. If the pH indicator's pH change is known and we use it to determine the unknown: the pH of the solution, what if the pH of the solution is known? — Edward Z. Yang(Talk) 20:50, 23 May 2006 (UTC)
thread_title:  pH indicator's color range 

message: Is pH basically the number of hydrogen ions in a solution? The higher the number of hydrogen ions the greater the pH and the more basic?
If so the why would amino acids lose Hydrogen ions in a high pH solution if there is a greater concentation of H outside the amino acid envrionment? 
Am i making sense and have i got it all wrong? Thanks in advance.
: When asking questions like these, please use the reference desk in the future. However, I'll give you two terse answers: yes except in extremely concentrated solutions and no you've got it reversed. — Edward Z. Yang(Talk) 13:34, 30 May 2006 (UTC)
thread_title:  Number of Hydrogens? 

message: Can we have a explanation of 'pH' in laymen's terms? Doesn't need to be a long thing just a paragraph or two. I don't know this stuff real well. :)
:Well, the first paragraph should be in laymen's terms. What do find about it that's hard to understand? — Edward Z. Yang(Talk) 20:52, 31 May 2006 (UTC)
thread_title:  Can we have a explanation of 'pH' in laymen's terms?  

message: Why don't create a link to know what the ionization constant od water is!
: Self-ionization of water, which is on the menu at the top of the article. — Edward Z. Yang(Talk) 19:31, 8 June 2006 (UTC)
thread_title:  Question: 

message: the H is for hydrogen. What does the p stand for? Simply south 21:18, 13 June 2006 (UTC)
replies: text: See last paragraph of the introduction. —Keenan Pepper 22:22, 13 June 2006 (UTC)
thread_title:  pH itself 

message: Substituted at 21:51, 3 May 2016 (UTC)
thread_title: Assessment comment