# 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?

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pH = - log[H3O+]

- log[H3O

^{+}] = pHlog[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 '10

^{x}'This is the key you want.

So I press '2nd function' button and then the log button which on 2nd function is the 10

^{x}keySo the key to look out for is the 10

^{x}key.Hope you can follow this.

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

^{+}] concentrationkingchemist

Mon, 2009-12-14 14:40

Thank you thank you so much!

Swtchk

Mon, 2009-12-14 14:55