Talk:Buffer solution

pKa

I think this is confusing.. pKa is the p value of H3O+ but in the example it is also the p value of the accid A-? —Preceding unsigned comment added by 86.90.133.91 (talk) 21:06, 31 January 2010 (UTC)

removed section

Question about buffers, and maybe this can be added, but why are they usually named after the conjugate base? —Preceding unsigned comment added by 198.110.194.81 (talk) 18:42, 8 September 2008 (UTC)

I removed a section "Illustration of a buffer solution in action" because, to me at least, it was redundant with the following section, and the less well presented of the two. I hope that doesn't cause consternation. Olin 03:35, 9 March 2006 (UTC)

I did some further cleanup, although the article still needs some help. Olin 04:10, 9 March 2006 (UTC)

I have changed the equation of calculating the PH. The HA and A- was wrong way round. This is further confirmed through text book.

I changed it back, per Henderson-Hasselbalch equation. I'll look it up when I get a chance. Tom Harrison ^Talk 14:19, 6 June 2006 (UTC)

Deduction:

1. $\mathrm {K_{a}={\frac {[H^{+}][A^{-}]}{[HA]}}}$
2. $\mathrm {[H^{+}]={K_{a}}{\frac {[HA]}{[A^{-}]}}}$
3. $\mathrm {log_{10}{[H^{+}]}=log_{10}{(K_{a})}+log_{10}{\frac {[HA]}{[A^{-}]}}}$
4. $\mathrm {-log_{10}{[H^{+}]}=-log_{10}{(K_{a})}+-log_{10}{\frac {[HA]}{[A^{-}]}}}$
5. $\mathrm {-log_{10}{[H^{+}]}=-log_{10}{(K_{a})}+log_{10}{\frac {[A^{-}]}{[HA]}}}$
6. $pH=pK_{a}+log_{10}{\frac {[A^{-}]}{[HA]}}$

QED. IMHO, the formula stated is the correct one. --Dirk Beetstra 15:34, 6 June 2006 (UTC)

ah ha....sorry, forgotten about the -log. thanks for reverting it back.

more buffers @ sigma-aldrich

Spam link! I do not see and kind of scientific value!

http://en.wikipedia.org/wiki/User_talk:213.188.227.119

Best regards

Look, Scotty has beamed them to a more appropriate position, just as this remark of you! --Dirk Beetstra 16:21, 29 May 2006 (UTC)

Link title

"as the equilibrium moves to the right " What does this mean? Xxanthippe (talk) 01:29, 3 July 2008 (UTC).

Major revision

This article was in desparate need of a thorough revision.

I have generally streamlined the text and

• shortened the lead-in to essential definitions and added chemical context
• moved details from lead-in to a theory section
• removed waffle and atrocious diagrams. Details concerning titrations are not relevant here.
• added a section on buffer capacity
• added simple and universal buffer mixtures
• added four significant references

The applications section does not, at present, do the topic justice, I don't have the time to do this. See acid dissociation constant for some other applications, with references. Petergans (talk) 18:47, 27 August 2008 (UTC)

possible error in the buffering capacity equation

As far as I know, in the equation describing the buffering capacity there is an error. The last term should be multiplied by the proton concentration [H+]. In other words the term Ca*Ka should appear as Ca*Ka*[H+]. See e.g. http://www.chembuddy.com/?left=pH-calculation&right=pH-buffer-capacity.

157.27.253.226 (talk) 14:43, 11 September 2008 (UTC)Roberto Chignola

You are right, many thanks. I will modify the article accordingly and re-do the plot. Petergans (talk) 19:35, 11 September 2008 (UTC)

I have corrected the formula. The correct formula was in fact used in the spreadsheet with which the plot was produced, so the plot is OK and the figure of 33% is also OK. Petergans (talk) 19:42, 11 September 2008 (UTC)

pH of buffer and temperature

I think it is necessary to add a section highlighting that the pH of a buffer depends on temperature and this in turn varies for different acid/base systems. People in biosciences and medicine use a lot of systems with an optimal temperature of 37 C but forget that the 0-14 pH scale with neutral pH at 7.0 is at 25 C. Having worked in different labs I have seen many people making mistakes in reporting the pH of biological samples or preparing buffers with the wrong pH value for the temperature that they are going to be used at. Is someone, with experience in editing wiki articles, willing to do that? Cheers. —Preceding unsigned comment added by 79.107.250.250 (talk) 14:46, 14 July 2010 (UTC)

Why does the pH change less in a buffer solution?

This article is missing the "why". I think it would really benefit from an explanation of why pH changes in a buffer solution are smaller than in a non-buffer solution. —Preceding unsigned comment added by 207.81.119.184 (talk) 02:55, 15 October 2010 (UTC)

@207.81@.119.184 what makes the ph goes higher after the rain in dams 41.114.140.182 (talk) 05:13, 20 January 2024 (UTC)

I've added a section outlining this called principles of buffering, as well as reorganising some of the sections which were all under 'acid dissociation constant'. PiFanatic (talk) 17:10, 15 January 2011 (UTC)

I don't understand this article at all

84.72.8.4 (talk) 19:41, 31 July 2011 (UTC)

Buffer capacity

The last sentence of the "Buffer capacity" section reads:

<<With specific values for C0, Ka and y this equation can be solved for x. Assuming that pH = -log10[H+] the pH can be calculated as pH = -log10x.>>.

I think it should be "-log10(x+y)",since [H+]=x+y in the ICE table. — Preceding unsigned comment added by Jose Brox (talk • contribs) 04:42, 26 February 2013 (UTC)

Absolutely not! y is used in the calculation of the hydrogen ion concentration (x) but pH depends only on x. Petergans (talk) 06:30, 26 February 2013 (UTC)

---

The current equation is incomplete, and the explanation of the increase in buffer capacity at the periphery is incorrect. The proper equation is as follows:

$\beta \equiv {\frac {d[B]}{d(pH)}}=\ln {10}\left([H]+{\frac {K_{W}}{[H]}}+\sum {\frac {CK_{a}[H]}{(K_{a}+[H])^{2}}}\right)$

This equation correctly explains the increase in the periphery buffer capacity as the buffer capacity due to water (the [H] and Kw/[H] terms). A simple numerical simulation with and without these terms proves they are responsible for the periphery increases. This equation also elucidates how the buffer capacities of a mix of buffers interact (they're additive).

For sake of completeness here's a derivation of the above equation:

${\begin{aligned}1:&K_{a}&=&{\frac {[A^{-}][H]}{[HA]}}\\2:&[HA]&{\overset {1}{=}}&{\frac {[A^{-}][H]}{K_{a}}}\\3:&C&=&[A^{-}]+[AH]\\4:&C&{\overset {2}{=}}&[A^{-}]+{\frac {[A^{-}][H]}{K_{a}}}\\5:&C&=&[A^{-}](1+{\frac {[H]}{K_{a}}})\\6:&[A^{-}]^{-1}&=&C^{-1}(1+{\frac {[H]}{K_{a}}})\\7:&[A^{-}]^{-1}&=&C^{-1}+{\frac {[H]}{CK_{a}}}\\8:&[A^{-}]^{-1}&=&{\frac {K_{a}}{CK_{a}}}+{\frac {[H]}{CK_{a}}}\\9:&[A^{-}]^{-1}&=&{\frac {K_{a}+[H]}{CK_{a}}}\\10:&[A^{-}]&=&{\frac {CK_{a}}{K_{a}+[H]}}\\11:&K_{W}&=&[OH][H]\\12:&[OH]&=&{\frac {K_{W}}{[H]}}\\13:&[B]+[H]&=&[OH]+\sum [A^{-}]\\14:&[B]&=&-[H]+[OH]+\ sum[A^{-}]\\15:&[B]&{\overset {12}{=}}&-[H]+{\frac {K_{W}}{[H]}}+\sum [A^{-}]\\15:&[B]&{\overset {10}{=}}&-[H]+{\frac {K_{W}}{[H]}}+\sum {\frac {CK_{a}}{K_{a}+[H]}}\\16:&[H]&=&10^{-pH}\\17:&{\frac {d[H]}{d(pH)}}&=&10^{-}pH\,\ln {10}\\18:&{\frac {d[H]}{d(pH)}}&=&[H]\,\ln {10}\\19:&\beta &\equiv &{\frac {d[B]}{d(pH)}}\\20:&\beta &=&{\frac {d[B]}{d[H]}}{\frac {d[H]}{d(pH)}}\\21:&\beta &{\overset {18}{=}}&{\frac {d[B]}{d[H]}}(-1)[H]\,\ln {10}\\21:&\beta &=&-[H]\ln {10}{\frac {d[B]}{d[H]}}\\22:&\beta &{\overset {15}{=}}&-[H]\ln {10}{\frac {d}{d[H]}}\left(-[H]+{\frac {K_{W}}{[H]}}+\sum {\frac {CK_{a}}{K_{a}+[H]}}\right)\\23:&\beta &=&-[H]\ln {10}{\frac {d}{d[H]}}\left(-[H]+K_{W}[H]^{-1}+\sum CK_{a}(K_{a}+[H])^{-1}\right)\\24:&\beta &=&-[H]\ln {10}\left(-{\frac {d}{d[H]}}[H]+K_{W}{\frac {d}{d[H]}}[H]^{-1}+\sum CK_{a}{\frac {d}{d[H]}}(K_{a}+[H])^{-1}\right)\\25:&\beta &=&-[H]\ln {10}\left(-1-K_{W}[H]^{-2}-\sum CK_{a}(K_{a}+[H])^{-2}\right)\\26:&\beta &=&-\ln {10}\left(-[H]-{\frac {K_{W}}{[H]}}-\sum {\frac {CK_{a}[H]}{(K_{a}+[H])^{2}}}\right)\\27:&\beta &=&\ln {10}\left([H]+{\frac {K_{W}}{[H]}}+\sum {\frac {CK_{a}[H]}{(K_{a}+[H])^{2}}}\right)\end{aligned}}$ Tristyn^⌘ 14:20, 2 February 2019 (UTC)

Simulated titration diagram

The png is inadequate

• The letter size of AH, pH and A^- is too large. It does not correspond to other lettering in the diagram
• The placing of AH etc. is not clear enough
• The caption A- is incorrect. It should be A^-
• The labelling on the right axis (pH) is horizontal. This is inconsistent with the left axis label.I have reverted to the svg. I can convert this diagram to png, using PaintShop, and shall do so in the next few days. Petergans (talk) 09:02, 29 July 2015 (UTC)

What is buffer??

I don't understand,too. David Kevin (talk) 02:57, 30 January 2016 (UTC)

In this conext it is to do with chemistry. When some acid (or alkali) is added to a buffer solution the pH of the solution does not change as much as when the same amount of acid (or alkali) is added to a solution that does not contain a buffering agent. Here is a simple example to do at home: take a sip of some lemon juice, then add a pinch of baking soda (bicarbonate) to it and take another sip. It still tasted tart. But, if you add the same amouint of baking soda to a glass of water it will taste different. You can check the pH of the solutions with litmus paper. Petergans (talk) 08:50, 30 January 2016 (UTC)

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