2011 AP Chemistry Exam – Free Response Comments

May 05, 2011

An ODD year this year.

Normally I have kids leave the exam (literally) saying that they were disappointed that they had not been challenged more. This year a few of my very best kids came to see my afterwards, saying that the exam was really hard and that they had some difficulty in finishing in time! I didn’t think much of that at the time, since I just assumed that the exam was hard and that they would still have done (as usual) really well. Indeed, I wasn’t at all surprised at their reaction because for a LONG time I’ve been expecting/hoping for a massive over-correction to make up for the fact that the AP exam in recent years has become so painfully easy. HOWEVER, when I saw the test I became a little more alarmed, since I did NOT think it was especially difficult at all. Sure, perhaps a little more challenging than in recent years in one or two places, but still very accessible. Now I’m worried! Here are my comments on the individual questions;

Question 1:

Apparently this REALLY threw a lot of my kids and they ended up spending too much time on parts (c) and (d) and massively over-thought the problem. I actually like the question a lot, as it represents a different approach to Ka and Kb than in the past. However I still don’t really understand the need to always have a K problem in question #1.

Question 2:

For the umpteenth time, if you want to really test a lab situation you HAVE to have a lab exam.

(a)(ii) is a minefield. The first thing that comes to mind is “why are AP kids handling 16 M acid at ALL”! This is an important consideration since I assume the ‘lab question’ is supposed to reflect some degree of real lab experience for these children. Secondly, as others have pointed out (thanks Paul), there could be an issue with using the ‘rubber’ gloves since they may be made from an inappropriate material to be using in conjunction with acid of that strength – I just wonder what they are hoping to get from this question. Thirdly there is the question of using the stirring rod to possibly ‘drizzle’ the acid into the water – IF that’s what they are looking for in an answer then IMO it’s a VERY obscure reference to a VERY specific, ‘not likely at AP level’, technique. How many AP teachers would have this conversation with their kids?

(a)(iii) Three different schools of thought here, I assume all will get credit. One relating to the significant figures used in the final concentration of the acid, one relating to the graduated cylinders already having introduced ‘the weakest link’ in terms of accuracy and one relating to the acid being used as an excess reagent.

Parts (b) and (c) of this question are things that I do with my ‘regular’ kids and IMO are just too easy.

Question 3:

(g) Token nod to environmental aspects!?

Question 4:

I still waiting for a pendulum swing to make question 4 once again worthy of being on an AP exam. I’ve just about lost all respect for this portion of the exam.

(b) I WISH they wouldn’t give big clues (‘to produce a coordination complex’) and assume that as has been the case traditionally, full credit will be awarded for numbers of ligands other than 4 as long as the equation is balanced correctly in terms of charge and atoms.

(c)(ii) I’m assuming one of at least three observations will get the point. (Blue coloration, solid silver forms, copper dissolves).

Question 5:

Not much to say other than I think it’s fair but way too easy in many respects.

Question 6:

Not much to say other than I think it’s fair but way too easy in many respects.

Overall the exam probably stepped up a notch compared to recent years, but it’s only ‘a notch’. I like question 1, but the exam is still a shadow of its former self and the net ionic equation writing remains a (post-2006) joke. My results will be more interesting to see than usual since the kids’ reaction does not seem to dovetail well with the questions – I’m a little concerned.

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