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13.23 How to find final pH?

Posted: Wed Nov 30, 2016 6:00 pm
by Yiling Liu 1N
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.

Re: 13.23 How to find final pH?

Posted: Wed Nov 30, 2016 6:15 pm
by Yiling Liu 1N
Edit: Thanks for the clarification!

Re: 13.23 How to find final pH?

Posted: Wed Nov 30, 2016 6:16 pm
by Chem_Mod
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.

Re: 13.23 How to find final pH?

Posted: Wed Nov 30, 2016 6:17 pm
by Chem_Mod
Apologies, I deleted my original reply as it was incorrect.