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On 5 Nov 2003 05:52:44 -0800, (Roy Basan) wrote:

>A pH or minus 4.5 or -4.5? Does a negative pH value exist like
>negative temperrature reading.I can not rememberr from my general
>chemistry class several decades ago. that if its possible for the
>hydrogen ion concentration to have negative values?

The hydrogen ion concentration [H] is an exponential in the negative
pH (aka "potential of hydrogen). That is,

[H] = 10^pH.

That concentration is in moles per liter.

>How can that be feasible a pH range from 1 to 14.From what I remember,
>The lower values is in the acidiic side(units 1 to 6) while the pH
>readings starting from above 7 is going to the alkaline side. The
>middle value 7 means neutral.

The mass action expression for neutral water is

[H] [OH] = 10^-14

and since the hydrogen ion concentration is equal to the hydroxyl ion
concentration, each is equal to 10^-7. That's where the pH of 7 comes
in.

If the solution is acidic, that means [H] > [OH] and [H] > 10^-7. For
example in a very acidic solution [H] could be 10^-2, which is
considerably greater than 10^-7. That would give you a pH of 2.

Bob

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