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Will it be possible to find the pKa value of two weak acids? I am working on a project for school on calculating buffer capacities and to find the pH of the buffer solution, I have seen that you need the Ka value of the acid used. However, in my case, I have two acids that are mixed (in a serum). So how will I go about finding the pKa of the mixture or is there any other way of finding the pH of the buffer solution.

The weak acids are glycolic and lactic acid.

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    $\begingroup$ As this is tightly related to your prior question, you could as well expand the original one. // Mixtures do not have pKa. It is an attribute of a particular acid, being tabelated and usually easy to find. $\endgroup$
    – Poutnik
    Commented Jun 8 at 6:24
  • $\begingroup$ There's no pka of mixture but you can calculate the pH.chemistry.stackexchange.com/questions/10249/… $\endgroup$
    – The Fright Of The Night
    Commented Jun 8 at 6:28
  • $\begingroup$ @Poutnik oh I am new to the platform. How do I do that? $\endgroup$
    – user146630
    Commented Jun 8 at 7:10
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    $\begingroup$ I am not sure what you mean. Expanding by editing, finding by searching. Both acids have their Wikipedia pages, including their pKa. $\endgroup$
    – Poutnik
    Commented Jun 8 at 8:20
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    $\begingroup$ What is the composition of the buffer solution ? One acid alone, or two acids alone do not make a buffer solution, without some basic addition. $\endgroup$
    – Maurice
    Commented Jun 8 at 14:50

1 Answer 1

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The Henderson Hasselbalch equation can be applied here.

pH = pKa + log salt/acid

pKa of glycolic acid 3.83
pKa of lactic acid 3.86

Potassium hydroxide is a strong base. It will react quantitatively with either acid to produce its salt.

Since the pKa of both acids is very close, the sum of their concentrations can be used in the equation, minus the amount that reacted with KOH.

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