Talk:pH

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Remove erroneous example[edit]

Removed the following because it is wrong. 5e-6 ions per mole of water equals 1 ion per 3.6 metric tons of water. I'm not sure what the correct formulation for this example would be, but the original is clearly off by many, many orders of magnitude.

In way of example, an aquatious solution with 5x10-6 hydrogen ions per mole of solution has a pH of:
hence,
— Preceding unsigned comment added by Ryanrs (talkcontribs) 13:18, 30 January 2016 (UTC)
To be exact, the example is off by a factor of exactly Avogadro's number. Why remove an otherwise numerically correct example when you could have fixed it simply by inserting "moles of" before "hydrogen ions"? (And correct "aquatious" to "aqueous".) Vaughan Pratt (talk) 22:53, 25 May 2016 (UTC)
This example (without "aqueous" since it holds for any solution) now appears near the beginning of the article, along with the example of pH of pure water. Vaughan Pratt (talk) 02:00, 26 May 2016 (UTC)

I agree with Pratt. Wikipedia often hides or omits the information one is seeking in a particular paragraph or even whole article (longitude latitude i had a dispute with, also meniscus, many others).

pH is the concentration (the simple ratio) of (H) + ions to neutral ions, so if the concentration is 10^-7 the pH is 7 which is called "neutral" (but is not zero). The paragraph dresses up the subject to be more difficult or even not the same as it is. The mention of logarithms has absolutely nothing to do with the matter, confuses the matter: and how to use logarithms is not described correctly or at all. the notation: varies from other text as well. — Preceding unsigned comment added by 72.219.207.25 (talk) 23:43, 20 April 2017 (UTC)

(I did exactly what i said not to unfortunately.) Most importantly: a pH of 10^-8 is less than 10^-6, a higher pH means less H+ ions and more anions (OH-, roughly speaking). It's a matter if simple counting. — Preceding unsigned comment added by 72.219.207.25 (talk) 01:23, 21 April 2017 (UTC)

pH and temperature[edit]

The dissociation product of water varies strongly with temperature. In hot water it much larger than 10^-14 which implies that neutral pH should be clearly less than 7, but maybe some type of normalization is used to keep it at 7. It would be good if some knowledgeable person could add a section on this issue. — Preceding unsigned comment added by 150.227.15.253 (talk) 08:56, 10 August 2016 (UTC)

pH is a measure of the thermodynamic activity (effective concentration) of hydrogen ions in an aqueous solution. When water dissociates, equal amounts of hydrogen and hydroxide ions are produced. They cancel each other out. The absolute concentration of hydrogen ions increases as the temperature increases, but the effective concentration, and therefore the pH, is unchanged. Trfeick (talk) 09:02, 19 August 2016 (UTC)

The p in pH[edit]

I have yet another interpretation of pH that was given to me by a very experienced chemist who has long since retired, and it is that p is as close as an English language typewriter can get to the Greek letter ρ (lower case rho), the chemical symbol for Inverse. Dick Kimball (talk) 16:23, 3 November 2016 (UTC)

Seawater[edit]

There is more written here about seawater than seems warranted, imho. I find the discussion of seawater and, for that matter, the entire article, flawed. There are multiple anions present in seawater and the most common are chloride, sulfate, bisulfate, carbonate, bicarbonate, bromide, and fluoride. The two "corrected" sea water scales mentioned do not mention carbonate/bicarbonate at all. There is no general purpose way to correct the membrane potential (or electrode potential) for specific interactions between the surface and chemicals present in the solution (these may include colloidal and even suspended solids). It is usually necessary to remove the dissolved gasses present in seawater to get consistent readings. Unfortunately, that compromises the goal of the measurement, it affects the pH of the liquid. There are plenty of PRACTICAL books on pH which basically say that the best definition of pH is what a properly calibrated and standardized pH meter measures. (With the implicit or explicit admission that this pragmatic approach will not produce the actual -log[A_h+].)98.21.243.206 (talk) 23:59, 4 May 2017 (UTC)