Klarinet Archive - Posting 000293.txt from 1999/12
From: "Jim Youngman" <youngman@-----.au> Subj: [kl] RE: then again... Date: Sat, 11 Dec 1999 00:06:37 -0500
NOTE: This may not be entirely off-topic. Music and mathematics are closely
related :)
"W. Edinger" wrote:
>
> Come to think of it, Roger may have had it right after all. Does
> "index" translate to "exponent?"
>
> 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?
>
Well, actually it's not a matter of American vs. British chemistry, it's all
to do with maths.
Let's accept Bill's definition of the dissociation constant as 10e-14, I
don't remember enough of Chemistry 1 to be sure of definitions. The square
root of this is 10e-7, and the log square root is -7. Roger's formula would
yield a value for the pH as -10e-7, while the value of Bill's "half of
10e-14" is actually 5*10e-15. The correct formula for the calculation is:
-log(sqrt(dissociation))
or, alternatively:
- (1/2)*log(dissociation)
Both of these are mathematically equivalent. Perhaps Bill or Roger can give
the physical meaning. "A mathematician is a person who doesn't know what
he/she is talking about, nor whether it is true."
-------------------------------------------------------------------------
Jim Youngman
19 Portsmouth Street, Heathmont VIC 3135, Australia
Phone: +61 3 9893 1029 Fax: +61 3 9870 0636
mailto:youngman@-----.au
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teenei te tangata puuhuruhuru
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