13.23 How to find final pH?

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Yiling Liu 1N
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Joined: Sat Jul 09, 2016 3:00 am

13.23 How to find final pH?

Postby Yiling Liu 1N » Wed Nov 30, 2016 6:00 pm

5mL 0.010M NaOH (aq) is titrated with 0.005M HCl (aq)

What is the pH of the final solution?

I don't understand how the answer key got that the final pH is 2.54, when 30.0 mL of HCl was added. Besides for trial-and-error, I don't really see a way to solve for the final pH. I understand that the pH at stoichiometric point in this case is 7, since the titration is between a strong acid and strong base. But in terms of the final pH, I don't know how to calculate this when the amount of titrant was not given.

Yiling Liu 1N
Posts: 25
Joined: Sat Jul 09, 2016 3:00 am

Re: 13.23 How to find final pH?

Postby Yiling Liu 1N » Wed Nov 30, 2016 6:15 pm

Edit: Thanks for the clarification!
Last edited by Yiling Liu 1N on Wed Nov 30, 2016 6:19 pm, edited 2 times in total.

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Re: 13.23 How to find final pH?

Postby Chem_Mod » Wed Nov 30, 2016 6:16 pm

At the end of a titration (not the equivalence/stoichiometric point), you will have used all of the acid in the buret, which often times holds approximately 25-30 mL. Essentially, they are using an excess of HCl at the end of the titration and calculation the pH based on that number, taking into account the moles of NaOH neutralized prior to reaching the equivalence point.

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Re: 13.23 How to find final pH?

Postby Chem_Mod » Wed Nov 30, 2016 6:17 pm

Apologies, I deleted my original reply as it was incorrect.


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