The 2013 AP Chemistry Exam Free Response analysis

Comments

Lots of my students said that they thought that the exam looked (or felt), different, and that questions were somehow ‘unusual’. I completely disagree and am a little concerned!

Sure, on balance the FRQ’s were perhaps slightly harder than they have been in recent years, but I don’t think that the exam really was different in any significant way. In any case, the total difficulty of the exam is spread across the FRQ and the MCQ, so if the MCQ were relatively easy, then the total exam difficulty would not have changed much. Here are some thoughts on the individual questions.

Question 1

A Ksp question that seems a little more involved than usual. I see no point in asking (b)(i) and (b)(ii) separately. What I mean y that is that in the past, that question was a profoundly more difficult one, where the two salts involved did not include similar ion ratios, and did not have similar concentrations for the non-common ion. Also, the question used to expect the kids to KNOW that they had to calculate the minimum fluoride ion concentration to work out which one would precipitate first by simply asking, ‘which will precipitate first?’ (rather than leading them through the process by telling them what to do in terms of the need to calculate the fluoride ion concentration!) For an example of what I mean, see 1985, 1(c).

To me, another tangible example that the exam is a shadow of its former self, which does not contradict the fact that this year was a little more difficult than in recent years.

The small volume of NaF that is generated in (b)(iii)will probably have some kids second guessing their answer.

It will be interesting to see what is accepted in (c).

Question 2

I see nothing of great gravity here.

Question 3

Not a big fan of lab questions  and data analysis (if you want to test lab, then have a lab exam), but of course this IS the future. Expect heavy emphasis on things like (b) and (f) in the 2014 and beyond – arrrggh.

Question 4

As we all know, this question has been dead in the water for many years. I’m not sure why it has been decimated in this way over the years, but it may be a reflection upon the College Board’s insistence on ‘inclusion’. They argue that this question STILL distinguishes between good, average and poor candidates. If that’s true, and I believe that it is, then there are way too many kids taking AP chemistry that simply should not be. I’m sad about the NIE’s, since I think that the exam has been hopelessly dumbed down by their dilution. Complex REDOX anyone?

Question 5

Tricky part here is (e), where the need to realize the Eact of the slow reaction is bigger than Eact for the second step. Lots will miss this, or at least lots will not realize it. The question *may* be flawed in as much as kids that don’t even think about that, might still get it right!

Question 6

We’ve seen part (d) before, but to be honest even I read it incorrectly the first time before correcting myself! It came up in 2008, 6(d) where there was a comparison between the LDF’s in relatively large chlorine and the dipole-dipole interactions in relatively small HCl.