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November 01, 2025, 11:32:36 am
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Author Topic: What is the pH?  (Read 741 times)  Share 

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lacoste

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What is the pH?
« on: September 12, 2009, 09:58:52 am »
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How do I work out this problem.

I tried working out the excess-reactant but some how i think i did it wrong.


the q:

100ml of NaOH of pH=13 and !00ml of HCl pH=1 ?


Thanks.   
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ryley

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Re: What is the pH?
« Reply #1 on: September 12, 2009, 10:36:12 am »
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Just looking at it quickly, I'm not sure if that actually is an excess-reactant question, aren't they in the correct mole ratio according to the reaction between the two?
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Mao

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Re: What is the pH?
« Reply #2 on: September 12, 2009, 07:28:59 pm »
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NaOH: pH = 13 --> pOH = 14 - pH = 1, hence [OH-] = 0.1 M, n(OH-) = 0.01 mol
HCl: pH = 1 --> [H+] = 0.1 M, n(H+) = 0.01 mol

they are in stoichiometric ratio, hence they neutralize and pH = 7.
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lacoste

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Re: What is the pH?
« Reply #3 on: September 12, 2009, 07:33:49 pm »
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Quote from: Mao on September 12, 2009, 07:28:59 pm
NaOH: pH = 13 --> pOH = 14 - pH = 1, hence [OH-] = 0.1 M, n(OH-) = 0.01 mol
HCl: pH = 1 --> [H+] = 0.1 M, n(H+) = 0.01 mol

they are in stoichiometric ratio, hence they neutralize and pH = 7.

Thanks! So when ever the mols are in exact proportion we assume that the pH is 7?
What I did was that I added up the mols then divided by the total volume, however, I didnt get pH of 7.
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