[CHM 112] CHM 112 Buffers Lab

[Andrew J. Pounds]

On 03/29/2015 12:25 PM,  wrote:
>
> Hi Dr. Pounds,
>
> This is from CHM 112. I have a question about the buffers lab that's 
> due Tuesday. I wondering how you wanted us to calculate the pKa of the 
> buffer and the Ka of the acid. I was thinking I would need to use the 
> concentration of the acid, but I see that we were only given the grams 
> of the unknown acid, without its molar mass. Please help. Thanks!
>

So at the midpoint of titration (halfway to the endpoint) the pH is 
equal to the pKa.  In the experiment you split your uknown in two and 
titrated it to the endpoint.  You then recombined the two solutions.  By 
definition the recombined solution was at the halfway to then endpoint.  
You measured the pH then -- and that should also be the pKa.


-- 
Andrew J. Pounds, Ph.D.  (pounds_aj at mercer.edu)
Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627
http://faculty.mercer.edu/pounds_aj

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