"Spike" wrote in message
...
On Wed, 2 Feb 2005 15:46:58 -0000, "Brian Reay"
wrote:
I thought the pH scale came from "per Hydronium"- H30+ ?
If the 'extra' H came from the water, then there would also be OH- to
neutralise it.
pH is defined as the negative of the logarithm of the hydrogen ion
concentration.
In pure water the product of [H+][OH-] is very close to 10exp-14,
where square brackets indicate concentrations.
So, if the water was being 'split', the concentrations would be the same.
Hence in pure water pH = 7 because the concetrations of the two
species are equal.
An acid solution, where [H+] is greater than that in water, has [H+]7
Ah, that sounds familar!
There is a more exact definition involving hydrogen ion activity.
That I don't recall, maybe it was beyond A level ;-)
--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898