My 2023 AP Chemistry Free-Response DRAFT ANSWERS are linked at the bottom of this post. Please let the know where I have made errors and typos, and I will be happy to amend.
Again, this is a staggeringly simple examination for what is supposed to be the gold standard in US, high school chemistry education. Of course, many children will struggle with it but that is absolutely not a function of the difficulty of the exam, but rather a continued function of the fact that thousands and thousands of kids that have absolutely no business taking AP Chemistry are still be placed in the course for nefarious, and cosmetic reasons. The perception of achievement still outweighs actual achievement; it’s the modern way. The utter obsession with particulate diagrams continues – we know why, someone is drinking the ‘research’ Kool-Aid.
On to the questions themselves.
(a)(i) I believe that if the question says, ‘complete’, that noble gas core representations should not be accepted. Of course, they will be.
(ii) A much better way to ask this question is to ask for the electronic configuration of a positive ion. That way it asks the orbital, and tests if the student knows electrons should be removed.
(b)-(e) I don’t know if the CB/TDC thinks that this type of question is ‘testing lab work’, but if they do they are grossly mistaken. This is a typical example of a stoichiomtery problem that has no relationship to anything that may (or may not) have gone on in the lab during the year. for the BILLIONTH time, if you want to test lab work, have a lab exam.
(d) It’s staggering to me that more teachers don’t say something like, “all formulae are simply the ratio of the moles of the components’. In my experience that helps a lot.
(f)(iv) In my answer I didn’t say, ‘conservation of mass’, but I think that you could as long as you say, ‘sealed’ or ‘nothing can escape’ with it.
(b) I don’t know why the question uses the words, “using reactions 2, 3 and 4”. Shouldn’t we leave it up to the student to work out what to do? Seems like too much spoon-feeding to me, but this is a common issue of course.
(c)(ii) I suppose that as long as this is worth only 1 point, then the approx. x and y values for the trough will be enough (with a similar shape), but I do worry that if it were worth more points then there could be some subtleties associated with the starting and finish positions of the curve. I suspect (hope) that I am overthinking this a bit.
(d)(i) and (ii) Lots more interesting questions could be asked around those diagrams. Resonance? Actual bond angles?
(a) Such a shame that equation writing has been decimated in the modern exam. Why give the full equation? This is sad.
(e) At least this is a stoichometry question that has some depth. I’d have love to have seen a back titration instead, but those days are gone forever I fear.
(g) Why give the total mass? I’d prefer making that part of the question.
(b) Again, if anyone thinks this is sufficiently testing lab work, then they are nuts!
(c) Very lame. SO much more you can do with buffer calculations. Yes, I know it’s only for 1 point here, but buffers! It’s the one place that really strong kids can distinguish themselves.
(a)(i) What would an AP exam be without P V = n R T??
(ii) Eighth grade physical science class.
(c) Imagine a prickly Ka calculation here instead! Oh for rigor!
(a) Why do we have a table?
(c) Quite a lot of stuff on bond length overall on the exam, a bit of an odd topic to emphasize.
(a) I would like an alternative answer to say that some associated ionic formula units should be shown since the presence of a Ksp suggests a relative lack of solubility. Yes I know the question says “ions present” but those ions could associated too.
(b)(i) The level of hand holding is shocking here, asking the first part of the calculation prior to (b)(ii). Oh well …
(c) Why not a common ion calculation instead?