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Old 10 Jun 2008, 4:49 PM   #5 (permalink)
EvozRule
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Re: ph acid/base question?

Quote:
Originally Posted by riadnicolas
How much water must be added to a 1 litre soln of a strong base of ph 13 in order to decrease the ph to 12?

I understand questions that ask to increase the ph but this one seemed new to me.

10^-14 = [OH-] [H3O+]

-log[H3O+] = pH = 13

Therefore [H3O+] = 10^-13

For pH = 12, [H3O+] = 10^-12

Since you're increasing the the concentration of H3O+ ions by 10^1, i.e you multiply 10^-13 by 10 which gives you 10^-12, you are increasing the volume 10x.

So so add 9L to it. Sorry if I cant explain properly not very good witht the theory side of chem

:-S
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