[CHM 112 Lab] lab

[Andrew J. Pounds]

> Hello Dr. Pounds,
> I know it's late to ask questions regarding the lab, but i wanted to 
> try everything i know before asking you, but i can't figure it out. In 
> Acid/Base lab, we should have three plots right? and i managed to do 
> two of them, but i don't know how to do the third one that has two 
> equivalence points. It was mentioned in the procedure that we didn't 
> have to record the volume of the NaOH used, so i don't get how i can 
> plot a graph using only different values of pH. Also, when you said 
> that pH= pka, did u mean the pH at the equivalence point (half-way 
> point on the titration curve).
> Thank you.


There are only TWO PLOTS for the pH and titration lab -- one for the 
strong acid / strong base titration and one for the weak acid / strong 
base titration.   You do not need a plot to determine the pH of your 
unknown acid (which only has one equivalence point). I went over this in 
class.  Please see your class notes.  The pH equals the pKa at the 
halfway point to the equivalence point. Look at a pH curve and ask 
yourself why did you recombine the two solutions (one titrated to the 
endpoint and one not titrated at all) before measuring the pH?


-- 
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