Adrian Dingle’s Chemistry Pages - The Blog

Thinking about taking the Organic Elective in the future?

It COULD be a BIG help in the future! Here is an email that I received from an ex-organic student in June of 2008 as he is taking a summer enrichment course at Stanford University.

“……………I’m at Stanford taking organic chem classes. These first four weeks, Sarah and I are taking an introductory course, and we’re cruising. Seriously, everytime he says nucleophilic substitution, me and sarah are like “we got that, thanks to Dingle.”

Congratulations….

…to ALL of my remote (long-distance) tutees that ALL scored 5’s on the AP exam in 2008. GREAT job, I know that you all worked hard and your success is well deserved!

Site Maintenance

Throughout the remainder of May, June and July expect to see maintenance on the site. This is the time of year when I get around to making some larger changes rather than just the tweaking during the academic year. First job is to get all of the documents and pages that reference the 2008 exams up to speed. After that it will be getting the Organic materials and pages ready for the summer elective course, and after that it will thinking ahead to 2008-09. Next (academic) year I will be teaching Regular Chemistry as well as AP, so look for revamped materials and pages there too.

Crispy Bacon - it’s NOT fair (and not just to pigs)!

In January of 1998, a public exam in A LEVEL Chemistry in the UK (the closest equivalent of AP Chemistry in the US) featured a question that started as follows;

“Propenal, CH₂=CHCHO, is one of the materials that gives crispy bacon its sharp odour. In the following question assume that the carbon-carbon double bond and the aldehyde group in propenal behave independently.”

OK, nothing too sinister there you might think, but the recent comments on the AP Listerv about Question 5 on the 2008B form of AP Chemistry exam reminded me of the controversy surrounding this question from a decade ago.

In 2008, a few teachers complained about the wording of the question on the recent B form of the AP exam because they thought it was confusing to students whose first language was not English. The SAME complaint was made about the “bacon question” in 1998, where some teachers complained that students from cultures that did not eat bacon would be disadvantaged. I’ll let you make up your own mind!

Comments on the 2008B Exam

Here are my comments on the 2008B exam;

Question 1: EXTREMELY straightforward. Again, I fail to see the need for question #1 HAVING to be an equilibrium problem, and part (b) seems almost completely redundant in terms of being worth points, but…..there you go. I guess when you ask this stuff SO much there’s only a limited number of questions that can be generated.

Question 2: Again, EXTREMELY easy and the predictability of these questions on kinetics is just about off the charts. VERY little imagination shown here. I STILL hate the insistence on using “real” data;

NOTE TO COLLEGE BOARD: IF YOU WANT TO TEST REAL LAB SKILLS, HAVE A REAL LAB EXAM RATHER THAN A TOTALLY CONTRIVED EFFORT WITH SILLY “LAB” NUMBERS!

Question 3: ANOTHER very simple question, but at least there was a touch more imagination. I would like to see the combination of a simple stoichiometry reaction WITH something else like a REDOX reaction to broaden the scope of the questions.

In recent years we’ve seen some questions where a combo of skills have been asked in a single question, but here (especially question 2 and question 3 to some extent), that pattern seems to have regressed a little.

Question 4: I fail to see the need to TELL the candidates that Cl₂ IS an oxidizing agent (way too much spoon feeding). I’d rather not see more stoichiometry in (b)(ii) (in the wake of Q3). (c)(ii) is more challenging.

Question 5: I must say that I like the imagination shown in this question, it’s nice to see a different, refreshing approach. The chemistry is still pretty simple, but I’ll cut it some slack! Someone in the Listserv mentioned that it would be potentially hazardous for candidates who are not native English speakers which I think is a valid point, and probably not one the CB considered. Outside of that, nice to see.

Question 6: Well, it does break the pattern of Delta G/H/S question slightly, BUT there is only so much that one can ask about this stuff! There have been SCORES of questions about this subject and I think that we need a break from it.

2008B AP DRAFT Free Response Answers

My DRAFT 2008B Free Response Answers are now available here for a VERY LIMITED TIME. Please feel free to criticize and correct. DOUBTLESS there will be comments required!

2008B, 1

2008B, 2

2008B, 3

2008B, 4

2008B, 5

2008B, 6

Subscriber Updates

My 2008 Draft Free Response Worked Answers have been posted into the relevant subscriber areas (i.e. those subscribers with a 2000-07 subscription).

Dear College Board……Expanded Comments on the 2008 AP Exam

OK, so after some time to reflect on my initial reaction to the 2008 exam here;

Initial 2008 Comments

here are a few more thoughts on the 2008 AP exam.

OVERALL:

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.

SPECIFICS:

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 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.

2008 DRAFT AP Free Response Worked Answers now available as part of Subscription #5

Having placed my DRAFT AP Worked Answers for the 2008 Free Response on the site for download, they are know only available as part of Subscription #5 here;

http://www.adriandingleschemistrypages.com/subscriber.html

PLEASE NOTE: If you already have a subscription to the 2000-07 Worked Answers Package, I will be adding the 2008 Draft answers to your subscription within the next 48 hours or so.

Initial 2008 AP Exam Comments

My initial comments on the 2008 Free Response can be found here;

2008 AP Exam Comments

More extensive comments are found here; http://adriandingleschemistrypages.com/AdrianDinglesChemistryBlog/nfblog/?p=161