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Chemistry Forums for Students => High School Chemistry Forum => Chemistry Olympiad and other competitions => Topic started by: Sophia7X on April 10, 2012, 05:51:54 PM

Title: how to interpret this graph?
Post by: Sophia7X on April 10, 2012, 05:51:54 PM
http://portal.acs.org/portal/PublicWebSite/education/students/highschool/olympiad/pastexams/CNBP_021762

the question I am having problems with is #5.

The answer is supposed to be B but I can only get A. I used the highest point on the graph (probably around 70 mL) but it didn't work.
Title: Re: how to interpret this graph?
Post by: Borek on April 10, 2012, 06:10:02 PM
Approximate both left and right parts with a straight lines. Where do they cross?
Title: Re: how to interpret this graph?
Post by: Sophia7X on April 10, 2012, 06:25:19 PM
Approximate both left and right parts with a straight lines. Where do they cross?

oh, thanks! I didn't think to do that; I just drew a curve through the dots. 75 works.


On the same test, #35... why isn't this graph a diprotic acid?
Title: Re: how to interpret this graph?
Post by: Dan on April 11, 2012, 03:03:16 AM
Quote
On the same test, #35... why isn't this graph a diprotic acid?

For a diprotic acid, if the first equivalence point is reached after adding x mol of NaOH, how much more NaOH do you need to add to reach the second equivalence point?
Title: Re: how to interpret this graph?
Post by: Sophia7X on April 11, 2012, 03:59:58 PM
So it's not diprotic because the second equivalence point would require 2x?
Title: Re: how to interpret this graph?
Post by: Borek on April 11, 2012, 05:21:40 PM
Yes.