[dfodor]

Hi,

I would have a very basic question but apparently the opinions are not unique. So can you interpret pH in non water solutions? Theoretically you can calculate/measure the proton concentration in a for example HCl/EtOH mixture. Should the acid/base be an Arrhenius acid/base to correctly interpret pH?

Thanks a lot

Daniel

[DemonicAcid]

Yes.

[aeacfm]

even in the organic compounds the may be acidic or basic from where this come from from the protons exactly found in the compound and the reverse in the basic compounds like amines which are basic compounds all this was defined by   "Bronstead & Lowery"  which defines acids as proton donner and bases are proton accepetors  but Arrhenius said that the acids are proton donner and bases are hydroxyle ion donner  
finally the most recent and general formula of acid is electron donner compound
    and base is electron accepetors compounds

i hope i reply !!!!!!!!!!!!!!!!!

[dfodor]

DemonicAcid: to which question was this the answer?
Can you interpret pH in non water solutions? or
Should the acid/base be an Arrhenius acid/base to correctly interpret pH?

May I get a bit more detailed answer?

aeacfm: I know the acid base theories but the question is whether you can measure pH in solutions besides water.

[Borek]

Generally speaking it is not impossible, but I doubt you will be able to do it in practice. First of all - how are you going to calibrate electrode? You can't calibrate it in water and move it to other solvent, as pH scale is solvent dependent; you can't use known substances to prepare your own pH standards, as pKa values are solvent dependent.

[dfodor]

Thanks for you reply.
I do not want to measure pH it was just a question and I was not really sure. The calibration is a good point but is there any theoretical consideration why you can say it makes no sense at all? I mean you can for example calculate pOH if you know pH but this is only possible if you consider your acid as an Arrhenius acid which can be interpreted only as a water solution. Or something like this...

[Borek]

pH is defined as minus log of H⁺ activity, so in theory it can exist (and be measured, once experimental procedures are developed) in every solvent. Same about pOH. However, it doesn't follow that knowing one you can always calculate the other. In nonaqueous solutions presence of H⁺ doesn't imply presence of OH^-. For example if solution of dry sulfuric acid dissociation still takes place:

H₂SO₄ <-> HSO₄^- + H⁺

However, what is really happening is that H⁺ protonates sulfuric acid:

2H₂SO₄ <-> H₃SO₄⁺ + HSO₄^-

(and it is not just a theoretical construct, ion product - similar to water ions product - is quite high, [H₃SO₄⁺][HSO₄^-] = 10^-2.9) so you have H₃SO₄⁺ (in a way analogue to H₃O⁺) and conjugate base HSO₄^-. We can define pH for such solution, but we can't calculate pOH.

[aeacfm]

so Mr Borek for non aqueous solutions like crude oil how can i determine the pH of the solution also like lube oil ?
also what type of electrodes used ?
what is its theory ?
how it could be calibrated?

[Borek]

Search literature, I am not a handbook.

[AWK]

http://www.springerlink.com/content/87pbkkjpx34uhalv/

[dfodor]

Tank you AWK!