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Topic: how to interpret this graph?  (Read 4957 times)

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Offline Sophia7X

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how to interpret this graph?
« 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.
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Offline Borek

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Re: how to interpret this graph?
« Reply #1 on: April 10, 2012, 06:10:02 PM »
Approximate both left and right parts with a straight lines. Where do they cross?
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Offline Sophia7X

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Re: how to interpret this graph?
« Reply #2 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?
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Offline Dan

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Re: how to interpret this graph?
« Reply #3 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?
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Offline Sophia7X

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Re: how to interpret this graph?
« Reply #4 on: April 11, 2012, 03:59:58 PM »
So it's not diprotic because the second equivalence point would require 2x?
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Offline Borek

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Re: how to interpret this graph?
« Reply #5 on: April 11, 2012, 05:21:40 PM »
Yes.
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