OK, so after some time to reflect on my initial reaction to the 2008 exam here;
here are a few more thoughts on the 2008 AP exam.
Well, the trend for easier AP exams has continued. When comparing recent Free Response (and MC for that matter) to papers from the 70’s, 80’s, 90’s and even early 00’s, we can see that there has been a SIGNIFICANT lowering of the level difficulty. This year’s exam was no exception, BUT it was a little harder in places than the 2007 paper. In particular parts a and b of the net ionic equation writing were a little more challenging, but to be honest, after the ease of the 2007 NIE it could NOT have got any easier.
The exam is increasingly predictable. This year I predicted that a Kp question would be in the mix, and that the lab question would be in Part A. VERY easy predictions I thought, and BINGO, the College Board obliged. With very few exceptions, there is beginning to feel a serious lack of imagination about the whole exam.
Question 1: Here’s an off the wall, random thought – why MUST this question be about some aspect of equilibrium? Sure it’s an important topic but so are many others. I’ve never really understood the need for this, nor the need to tell candidates that this will be the case. Overall this was a pretty easy question. There are multitude of ways of solving part c ranging from the VERY simple (Dalton’s Law) to the slightly harder via an ICE table. I found myself creating a relative elaborate ICE table when it was NOT necessary, probably in the sub-conscious hope that the question would be harder. The question could have been made harder by not giving the pp of CO2 at equilibrium and working things in a different way. As an aside, I’d like to see the WHOLE question printed on ONE page. Don’t underestimate the distraction that splitting over two pages can be for the candidates.
Question 2: Again, very predictable (I flagged gravimetric analysis to my students the week before the exam, and that I thought the lab question would be in Part A). This is a nice question, BUT I HATE the idea of providing “real” data in the question. The increment in the data between the second and third heating provides no purpose IMO, and could lead to a really bright candidate doing some bizarre calculations in order to get around it. I know of a couple of kids that decided to average the numbers (which may be thought of as sensible), but this could introduce discussions about SIG FIGS. I fully UNDERSTAND why it is done, I just dislike it intensely. I’m not sure that I follow the need to ALWAYS ask the, “what happens when this screws up” part of the lab based question. Part c is sooooo predictable. It was also pretty obvious that the Lab question would form part of the calculator section this year.
NOTE TO COLLEGE BOARD – LET’S HAVE A LAB EXAM!
Question 3: Painfully easy and in that respect I’d be surprised if this were a good question to distinguish between students. (At least we have “nice” data in d-f).
Question 4: Well, the NIE HAD to get harder – they couldn’t get any easier compared to 2007! Hopefully a and b will yield more than one answer that gains full credit – traditionally, almost ANY complex has been allowed as long as charges are appropriate. I’ll be interested to see what the official answer to a(ii) is. Some better imagination shown in the follow up questions to a and b, too.
Question 5: In part a I would like to see the NEED to include state symbols – I think that it is part of the definition and therefore SHOULD be included – we’ll see. In part d it has been suggested to me that a structure where the three O atoms are double bonded to the Xe would be the answer since IT has a “better” formal charge than the Lewis structure with single bonded oxygen’s. Although it IS true that the FC is preferable, my opinion on this has always been the same; unless we are dealing with resonance, OR unless the question is specifically flagging a number of different structures that require distinction using FC (as in 2005, 6c(ii)), that candidates should NOT be looking for alternative Lewis structures every time that they draw one. IF they did, it would be chaos! Since the single bonded structure works it terms of octets & total number of electrons, AND there is no flag in the Q that suggests a FC discussion, I am trusting that the single bonded structure will work – obviously credit can be given for the “better” structure too.
Question 6: It seems as though the CB are afraid of Organic! I like the fact that some organic compounds are used in a and b, but it seems like a missed opportunity to ask about nomenclature or isomerism or some other, simple organic concept. Essentially a-d are all the same question (bonding related to properties), and is highly predictable. I was glad to see part d – the most imaginative question on the exam for sometime.
SUMMARY: All in all, I thought that this year’s paper, although harder in one or two places, still sets the bar way too low. The predictability of the exam is far too high IMO, and in places it lacks imagination.