Re: Calculating [H30+] from pH

The problem says that if the pH is 6.40, what is the [H3O+]? How do I do this on my calculator. It doesn't let me put decimals in the exponent area. It's a Casio fx-260 solar. Is there another way to do this?

pH = - log[H3O+]
- log[H3O+] = pH
log[H3O+] = - pH
[H3O+] = - antilog of pH

So how to key it in. (and what the heck are antilogs.

On my calculator, key in the pH, 6.40
Change the sign with the +/- key so the display shows -6.40
On my calculator (supermarket 'special') I have a log key which has a second function on the button which says '10x'
This is the key you want.
So I press '2nd function' button and then the log button which on 2nd function is the 10x key

So the key to look out for is the 10x key.

Hope you can follow this.

I get the answer 3.98 x 10-7 which is the [H3O+] concentration

Thank you thank you so much!

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