Klarinet Archive - Posting 000282.txt from 1999/12

From: Roger Shilcock <roger.shilcock@-----.uk>
Subj: Re: [kl] klarinet Digest 10 Dec 1999 09:15:01 -0000 Issue 1894
Date: Sat, 11 Dec 1999 00:06:26 -0500

On Fri, 10 Dec 1999, Tony Pay wrote:

> Date: Fri, 10 Dec 1999 15:20:16 GMT
> From: Tony Pay <Tony@-----.uk>
> Reply-To: klarinet@-----.org
> To: klarinet@-----.org
> Subject: Re: [kl] klarinet Digest 10 Dec 1999 09:15:01 -0000 Issue 1894
>
> On Fri, 10 Dec 1999 09:40:07 -0500, 100012.1302@-----.com said:
>
> > Message text written by INTERNET:klarinet@-----.org
>
> > > Come to think of it, Roger may have had it right after all. Does
> > > "index" translate to "exponent?"
> >
> > Yes it does.
> >
> > > Roger: "7.0 - that's the index (with sign changed) of the square
> > > root of the dissociation constant of pure water"
> >
> > > Bill: "negative log of 10e-14"
> >
> > > Are they the same thing? Anyone speak both British and
> > > American chemistry?
> >
> > Square root isn't the same as logarithm. But as you both say, 7 is
> > neutral water.
>
> I *think* that the point is that the dissociation constant is the
> *product* of the hydrogen ion concentration and the hydroxide ion
> concentration, and for water at some standard temperature this is equal
> to 10^-14 where the symbol ^ stands for exponentiation. The square root
> comes in because the hydrogen ion concentration and the hydroxide ion
> concentration are equal for water, each therefore being 10^-7 (the
> square root of 10^-14).
>
> Then the pH of water, being the negative log to base 10 of the hydrogen
> ion concentration, is 7.
>
> I believe that this relationship is sometimes written in terms of the
> exponents, and so additively rather than multiplicatively, as
>
> pH + pOH = 14
>
> We do in fact sometimes call exponents 'indices' in UK, so that figures.
>
> Why did you say you were wrong, Roger? Or am I misunderstanding you?
>
> Tony
> --
> _________ Tony Pay
> |ony:-) 79 Southmoor Rd Tony@-----.uk
> | |ay Oxford OX2 6RE GMN family artist: www.gmn.com
> tel/fax 01865 553339
>
> ... Madness takes its toll - please have exact change
Because what I said about the square root of the degree of ionization is
only relevant for a ph of 7. It would have nothing to say about the ph of,
say, a N/20 solution of acetic acid.
(Clearly, there are an undenumerable number of possible examples.....).
Yours,
Roger S.

>
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