2010 Exam Comments and DRAFT Answers

May 13, 2010
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Categories: AP | Miscellaneous

Below you will find my comments on the 2010 AP chemistry exam, and my DRAFT answers. PLEASE NOTE: The answers are my first draft and I will be very happy to receive comments and corrections. Thanks go out to an AP reader for taking a look and making suggestions – you know who you are.

Comments:

Question 1:
Standard fare. Lacks much imagination, I’m afraid.

Question 2:
Very, very easy.

Question 3:
Very, very easy.

Although it makes no difference to the question, the production of Mn3+ in the half-reaction where manganate(VII) is an oxidizing agent, seems a little esoteric and unnecessary to me. Now, perhaps under some circumstances it DOES do that, but in every reference I have ever seens at this level I have only ever witnessed it turning into Mn2+. In addition, Greenwood & Earnshaw, Chemistry of the Elements (known as the “green brick” and my go to guide on such matters) suggests that Mn2+ is the usual product. (G&E DOES mention that one “preparative route” to Mn3+ is “reduction of KMnO4”, but it also notes that Mn3+ has a “marked tendency to disproportionate”. My gripe here is NOT really about the chemistry (whatever it may be), but rather about the wisdom of suddenly having Mn3+ turn up as a product of the acid reduction of Mn7+ instead of (infinitely more usual) Mn2+. It seems like an unncessary diversion and something that could confuse potentially excellent candidates. It just doesn’t make much sense to me.

Question 4:
It seems as though the question writers have given up on this part of the exam. Possibly the easiest EVER? Why GIVE the colors in (a)(ii)? Why tell the kids a gas is produced in (c)(i)? The astonishing decline of complexity in this question in recent years is mildly depressing.

Question 5:
Very, very standard/easy.

(c) Delighted than ethanoic acid seems to finally be supplanting “acetic acid”! Hooray!

Question 6:
Very, very standard/easy.

If this represents a comprehensive and vigorous examination of the best, and highest level of chemistry being taught in American high schools then I think that we have a problem. I remain a HUGE supporter of the public examination/standardized test and its place, but this test simply does not add up to much of challenge at all. Quite weak and disappointing.

ANSWERS

6 Comments

  1. avogadro

    Answers are almost spot on with the ones I just finished writing up.

    Agreed that this test is lacking. I don’t mind the Mn3+. Shouldn’t scare them to seem something different.

    If you’re looking to be exact on the answers (personally I know I look just think about the sign in these cases), then on 2a usually Tf-Ti=dT. So -3.2 dC would be best. But either way, reasoning makes one figure out the signs later on.

    Reply
  2. haileyf

    Agreed. Far too easy. My students (who are generally NOT as motivated as the average AP Chem student) even thought it was easy. They were actually perturbed by the fact that the test told you the colors of btb in acidic and basic solutions, especially since I had forced them to memorize indicator colors.

    Reply
  3. willyxiao

    I agree. It’s coming down to a point where the exam is a test of who is the most meticulous and who won’t miss a question.

    Reply
  4. franknbrock

    Concerning 2. (c) (i)

    Are you sure you should add the 5.13 g urea solute to the 91.95 g of water?

    It is my understanding that only the temp change of the water mass is being measured and that heat lost by water is equal to the heat gained by the urea solute. In which case, m in q=mcdT is 91.95 which yields an eventual dH of 14 kJ/mol as given in 2. (d).

    Reply
  5. webmaster

    Re: franknbrock

    Well, I included the mass of both since the question stated that the specific heat capacity was that of the “solution”. I guess, we’ll see – maybe you are correct.

    Reply
  6. djharkavy

    Are your answers still available? Clicking on the link brings me to the page where it says that things are inaccessible.

    Reply

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