UTC: Tuesday, August 22nd, 2017

2017 AP Chemistry Released Exam Draft Answers & Comments

My 2017 AP Chemistry Released Exam Draft Answers & Comments appear below. The questions are here. These are DRAFT answers and may change as errors are pointed out to me, and other thoughts come to my mind. Should you find an error PLEASE let me know by commenting on this post below, rather than emailing me or using the contact form me (that way all problems can be addressed in this post), and I will comment/change as necessary.

PLEASE NOTE: Any of my comments below about how your individual answers might be graded, are highly speculative – you should not take them as fact.

General Comments

Many, many, many words. Reading comprehension rules more than ever, but overall an easy exam I think.

Specific Question Comments

Question 1

Not much to report here, although in 1(c)(ii) I suspect the effect of lone pairs is now well and truly dead and buried, so not only will a wide-range of angles be acceptable, they will probably be quite content with 109.5°.

In d(i) don’t put hydrogen bonding! It may or may not cost a point, but just don’t do it!

Question 2

In (a) a ton of people that CAN calculate formal charge will not get the point about negative charges residing on more electronegative atoms.

Question 3

Part (d) is tricky IF it wants something OTHER than capacity. The ratio change is a subtle point, and gets far too (indeed perilously) close to an exclusion statement for my liking, i.e., that the computation of changes in pH of buffers are not required. Yes, I know no calculation is required here, but still…

Question 4

In (b) I cannot imagine a calculation of Rf would be required.

Question 5

I’m confused by part (c). A MASSIVE amount of unnecessary text seems to complicate the question and the chemistry much more than required, but this is what the TDC/CB does these days. They want “storytime” context, and “real life situations”. Get ready for more of this nonsense.

I think that there is the possibility of DIFFERENT answers to mine scoring full credit! Maybe…

Question 6

Nothing to add.

Question 7

Nothing to add.

DRAFT ANSWERS

 

 

Comments

  1. 3c – I imagine that once the net ionic equation has been written, simply pointing out that when a weak acid and its conjugate (as shown in the equation) are present, the solution is a buffer, would be sufficient without discussing limiting factors. Also think it is probably 2 pts.

    3d. The number of moles of acid and base are 20 times greater in the second case. The second solution contains 0.1 mol of each, while the first is (as you wrote) 0.005 moles of each. I think it is sufficient to say simply that since the second solution contains more moles of acid and base, it can absorb more acid or base and remain a buffer.

    3e. I wonder whether a calculation is expected. My answer would simply have been that since moles acid> moles base, the solution must be more acidic than when they are equal, so pH< pKa

    5c. My NEW answer! Burning an alcohol -water mixture must produce less energy than burning pure alcohol, since the water doesn't burn. Therefore, the same mass of mixture must produce less heat, and a smaller temperture change. ( but your answer is fine!)

    • Melanie Dianda says:

      I initially answered 3e as you did Paul, but after seeing Adrian’s answer I asked myself why I didn’t solve it that way. I think that they will accept either answer (but I have never been a reader!). There does seem to be a trend away from calculations overall, so perhaps they were just intending for students to just be able to reason it out instead of to calculate it. If they did intend for a calculation then I feel they should have asked for the actual pH to lead students down the calculation path. From the answers I have seen on the forums, Adrian is the only one who calculated, which leads me to believe the majority of students did not calculate.

      • Calculation definitely NOT required.

        • for number 1.b.ii. shouldn’t the 30’C tail into the x-axis prior to reaching the activation energy?
          for number 2.a isn’t the formal charge for carbon 0 on both molecules?
          thanks

          • 1. No, it need not tail into the x axis. The prompt says “no reaction is OBSERVED to occur.” That does not mean that there are no collisions with sufficient energy, just that there are too few to produce an observable reaction.

            2. The carbon on the left has 4 bonded pairs of electrons. In counting for formal charge, that counts as 4, the same as carbon’s number of valence electrons. Formal charge is 0 The carbon on the right has THREE bonded pairs, plus one lone pair. That counts as 5. So that carbon has a formal charge of -1.

            Also, assuming that you found the +1 formal charge on the nitrogen, then SOME other atom had to be negative.

          • no, that’s not accurate. you only count an unbonded pair of electrons as one, not two.

          • my apologies, you are correct, my bad-i got it backwards.

    • Lisa Volaric says:

      5c. Another interpretation … If the water and alcohol are miscible and attracted to one another with H-bonding, both will be drawn into the wick. The heat released by the combustion of the alcohol will be absorbed by the water in the wick and less heat will be transferred to the water in the beaker. This source of systematic error results in a lower final temperature of the water in the beaker.

      • This one was common sense as well. Well, you needed to know what miscible meant to answer it correctly but it was literally common sense.

  2. That doesn’t look bad at all. The reading thing I do not have a problem with. Many students scoring 4s and 5s will likely attend schools with more rigorous chemistry sequences (and sadly, they will likely forfeit their credit). These rigorous instructors for general chemistry will put “wordy” (probably maybe even more wordy) problems to see if students can sift through information well. In fact, honestly, there were not many real world context problems here. It was always “a student did X”. This is not a big deal I would hope and it looks like most things came down to basically single concept plug and chug problems except for the couple of conceptual items. A more rigorous college general chemistry exam may have more of the structural/conceptual questions (and maybe even questions on orbitals), more “tricky” questions or even multi-concept questions (like they may be asked to relate thermodynamic data to pka). Here is an example:

    “For the decomposition of an anti-biotic in a person with normal temperature (98.6 F, 37 C), k = 3.1 x 10-5s-1 and for a person with a fever at 101.9F(38.8C), k = 3.9 x 10-5s-1. If the person with the fever must take another pill when 2/3 of the first pill has decomposed, how many hours should she wait to take the second pill assuming that the pill is effective after 30 minutes?”

    This comes from a private research university in Atlanta. I do not think it is too hard especially if AP students got exposure to doing problems like it in timed settings.

    Many taking this exam may be pre-medical in college and things like the MCAT require much more reading comprehension and extrapolation than this exam despite it only using multiple choice! Also, if one plans to pursue chemistry or any STEM degree in a research context, it is all about reading and dealing with complex scenarios.

    • Thanks for your comments. As for the reading thing, I guess it depends on what you think school is for, and what skills it needs to be delivering.

      • How many people do you think had absolutely no idea about the Buffers question? And if a lot of people completely bombed it, would they just drop it or put a huge curve?

        • A lot of people will be able to do it, to be honest, and questions are never “dropped”. The grade boundaries are set with the MCQ in mind too, so it’s a complicated beast, especially in the wake of the new exam.

          • I second this. That buffer question was exactly in line with the wording and goals of the new curriculum and is pretty much exactly how I describe buffers to my students. Buffers are one of the harder topics in AP chemistry in general, but many kids will do fine.

          • I don’t agree. I thought it was full of BS especially when they introduced mL. Like I didn’t know what to do. 1 and 2 were easy. 4,5 and 7 were also easy. But I had never learned buffers like that. I expected buffers to be 1 part to a greater question — not a whole question. That question will cost me the 5 I deserve.

          • Byron Chen says:

            I spent a lot of time with my students on buffers. In fact, I split the equilibrium applications into three tests: buffers, titrations, and Ksp. We also did a lab on designing an effective buffer. It was drilled into their minds that the pH = pKa at the half-equivalence point of a titration of a strong acid-weak base or strong base-weak acid (and that a buffer has been created at this point of the titration).

            That said, I agree with Matt’s point that buffers are one of the harder topics. I have found that too many of my students want to memorize their way through buffers and titrations, and the ones who are most successful at these topics are the ones can think their way through.

    • Byron. We learned buffers in the final 4 days of class. It was given to us as a side note for consideration (not something we studied at all).

      • Wow! How much time was your class able to spend on acids and bases overall? My colleague, who taught AP chemistry for many years, told me that students needed to spend at least a few weeks on acid/base equilibrium (especially buffers and titrations because they’re a large component of the AP curriculum’s Big Idea #6). In all fairness, though, all students in AP chemistry at my school have taken honors chemistry the preceding year, so we have more time than many other teachers do.

        • Well, we spent about 15 days on acid-base equilibrium (w/ titration curves). Then for buffers, we learned a stupid formula (Henderson hasselbach or something) and that was it. We didn’t learn the conceptual part of it, nor did we learn its applications. It was presented as if its insignificant. I just hope everyone else failed it.

          • Insignificant? That’s a shame. I might be in the minority here, but I find buffers quite interesting in how they work. And I love the Henderson Hasselbach equation because it can explain so much. Anyway, my students struggle a lot with buffers, and as you saw on the Reddit forum, so do a ton of other people. All the same, I hope you get the score that you want, buffers notwithstanding!

      • Adrian Adrian says:

        As Byron says, that is an entirely appropriate buffer question, predicted by me, that is 100% in line with the AP curriculum, and as such it is VERY fair. Buffers are a huge, integral part of the AP chemistry class, and to squeeze them in at the end, in a last minute rush, is a very, very bad idea.

        • Incidentally, Adrian, my students are grateful to you for the tip about reviewing titrations. We had a titration POGIL very similar to the one you had in your discussion, and my students especially studied the particle-level drawings. Thank you!

        • Sean Fisk says:

          I took your prediction to heart and did an extra few days reviewing buffers and conceptual titrations. Good call. Just hoping the International test looks similar.

  3. Nina Rodriguez says:

    Adrian,

    If you were to make a prediction of the total score cut offs for %’s, 4’s, 3’s, what would you predict?

    Last year:
    79-100 = 5
    64-78 = 4
    45-63 = 3

    • Almost impossible to do without seeing the MCQ’s, and in the light of the instability of the new exam.

      • MC was VERY EASY. Easier than last years for sure. But FRQs were a lot harder. Would you agree regarding the FRQs?

        • Honestly, I think the FRQ’s are pretty straightforward!

          • Jason Cook says:

            I agree. I was actually pretty suprised at how straightforward and approachable most of the problems were. Much easier than last year, in my opinion.

          • Ok so give me a range. I can tell you right now the MC was VERY EASY (I finished with 5 minutes left to spare and that is by working diligently — probably got 56/60 correct).

            So would you say the curve would be lower than 2015 and 16, or greater.

            Im just trying to get a sense of how I did.

          • Adrian Adrian says:

            It’s very difficult to tell. In the old days we saw a grade boundary for a 5 as low as the low-mid 60’s. On a recently administered new exam, it was 79. In addition to all of that, there was a VERY, VERY weird setting of boundaries by the College Board in 2015, when in my opinion, a ton of kids got screwed. In short, it’s difficult to predict, especially in the brave new world of AP chemistry that we are living in.

          • K Olsen says:

            Adrian, you said “there was a VERY, VERY weird setting of boundaries by the College Board in 2015, when in my opinion, a ton of kids got screwed” – could you refer me to this information, or a blog post you wrote? I would love to know more about this. Thank you for all of your work and sharing with us!

          • Adrian Adrian says:

            There’s this, and this, and when you look at my scores for 2015 they are BIZARRE.

    • Derek Stach says:

      And keep in mind Nina that those cut lines were for the International Exam… Have no idea what the cutlines for the Operational Exam were

      • I hope the curve is enough for me to get a 5. Otherwise, it’ll screw up my beautiful collection of 5’s ~~ 6 of them :)

        But that stupid buffer problem screwed me over. Like what kind of College Board writer thinks it’s a smart idea to put a FULL buffer problem on the AP Exam. Especially a 10 point question (he/she didn’t even have the decency to make it a short answer).

        I’ll be pissed if that’s the thing that ruins the score I deserve.

        • There are decades of problems based entirely around buffers. This is not a new thing. If your teacher didn’t prepare you for that, it is a shame, but the College Board has loved acid/base problems with buffers in them for a long time.

          • No. I’m not the only one that f’d the buffer one up badly. About 80% of the people I’ve spoken to on Reddit agree with me (and I’m under the assumption they actually learned it well ~~ unlike me).

          • Adrian Adrian says:

            The buffer question is VERY fair, completely acceptable, and absolutely straightforward.

          • I did the 2014,15, and 16 free responses and did very well on them. Only one of them had buffers and it was 1 part to a short answer question (it technically wasn’t even buffers — just being able to understand pKa and pH at half equivalence point, that kind of stuff..)

            The patricians who wrote this BS of a free response that screwed over many students should quit priding themselves and start writing reasonable questions that test a broader portion of A/B equilibria.

            I still can’t believe I scored a 2/10 on it. Initially, I didn’t care cause I aced the other parts but now it’s sinking in that I could miss the benchmark for a 5 (especially after reading your blog on the grading for the redesign exam).

  4. Will 103 degrees be accepted for the angle? It didn’t need a justification but I just talked about how it had 2 lone pairs

    :o

  5. Kara Woods says:

    In question 6, part a your answer is not consistent with your math for the grams of Magnesium Hydroxide. It should be 9.9 x 10-4 grams not 9.6 x 10-4 g

  6. K Olsen says:

    For 2(e), do you think it will be ok if students calculated several values of ln[CO(NH2)2] vs time and found a consistent slope? I’m sure several of mine did so (and hopefully noted that it was -0.693!)

  7. Jonathan says:

    #2 D says to answer the question in terms of thermodynamic favorability and the equilibrium constant. I understand what you wrote for that in terms of delta G etc. However, it does not address the equilibrium constant. I was thinking that because fulminic acid was a weak acid it would have a low K value and therefore be reactants favored? Also, with the reaction being exothermic, heat is product so as temperature got higher, it would become even more reactants favored based off LeChateliers principle? Maybe I am not thinking about it in the right terms or I am making assumptions I should not make? I look forward to feedback!

    • Adrian Adrian says:

      I think that I DID answer in terms of ‘K’ by saying that more products were formed, but I take your point that I could be a little more explicit. The problem that you have with the weak acid argument is that in this reaction fulminic acid is not acting as an acid, rather it is essentially a resonance situation.

  8. Jonathan says:

    I think I might have done 3e the harder way but got the same answer. I used the equation ln[A]t-ln[A]o=-kt. I am guessing this would receive credit as well?

  9. For 5b, it asks for the correct number of sig figs. Shouldn’t the answer be reported to 3 significant figures?

    • Adrian Adrian says:

      0.55 g is two sig figs. Honestly, sig. figs are nothing to do with chemistry and I am frustrated beyond belief with the CB’s unwillingness to clear up that particular mess. At this point, I’m getting beyond caring!

      • Sig figs are a load of sh*t. Just put the damn # down and round to 3 places like we do in AP Calc. What is this BS with the non-significant zeros. Like damn.

  10. Can you explain 1d ii. I know that CCl4 is said to condense faster but how?! CCl4 is nonpolar which means it has only london dispersion forces, but HCl has both dipole-dipole, and LDF’s, so shouldn’t HCl have stronger IMF’s than CCl4.

    • Adrian Adrian says:

      There have been many problems like this in the past, where the LDF’s of the much larger, but non-polar CCl4 molecules, outweigh the LDF’s and dipole-dipole IMF’s of the much smaller, but polar, HCl.

    • David N says:

      You could reason out that at the same temperature both CCl4 and HCl have the same kinetic energy… because CCl4 is in liquid state, the IMF’s were strong enough to cause attraction to other CCl4 molecules and caused the condesation. IMF > KE.

      The HCl being a gas at that temperature indicates that it’s IMF’s were weaker than the KE of the molecules and were not attracted to each other. IMF < KE.

      Just another way to think about it.

  11. I don’t understand why you are subtracting one of the cell potentials for 7c part a subpart i. Because both the dichromate and the hydrogen peroxide are being reduced as seen in the chemical equation. Shouldn’t the cell potential be 3.10 V?

    • Because both the dichromate and the hydrogen peroxide are being reduced as seen in the chemical equation. Shouldn’t the cell potential be 3.10 V?

      • Adrian Adrian says:

        You cannot have TWO reductions! One needs to be reversed, and when it is, the sign is changed.

        • Chromium experiences a reduction in oxidation state from +6 to +3; oxygen experiences a reduction in oxidation state from -1 (in peroxide) to -2 (in water). I believe both reduction processes should be accounted for. The oxidation process is the increase in oxygen’s state from -1 (in peroxide) to 0 (in oxygen gas). Thus the Ecell should be 1.33 + 1.77 – 0.70 = 2.40…?

          • See the balanced equation for the reaction. It shows the dichromate being reduced, and the peroxide oxidized. That is the redox reaction for which you must find Eo.

    • Lol. for this one, even if you didn’t know electrochem well, you could reason it out. XD

  12. For #1bi, if we just said the frequency of the collisions increases (without mentioning “with sufficient energy”), would we still get a point? I felt so stupid after I left the exam cause I knew I should’ve said with sufficient energy but blanked out.

    • Paul S Cohen says:

      I don’t think you get credit without mentioning higher energy collisions.

    • The 2014 AP Chemistry free response had a similar question on the last problem. In looking at the scoring guidelines, it seems that they do want a full justification, stating that an increase in temperature increases the kinetic energy. And it seems like they like references to activation energy. Then again, I’m not completely sure what the AP folks would accept.

      • In fact, I would be perfectly happy (and would hope it would get full credit) with a response that explains the increase in rate ONLY in terms of higher energy collisions, and does not mention increased collision frequency. The impact of increased frequency is pretty negligible compared with the impact of increased collision energy. ( the given increase in temperature would increase the RMS velocity by about 14 %)

    • Adrian Adrian says:

      I think you’ll have to have “higher energy” in there somewhere.

  13. I feel that on 1dii the intermolecular forces in HCl will be stronger than those of CCl4 because HCl is polar and has dipole-dipole bonds and LDF whereas CCl4 is non-polar and only has LDF?

    • Adrian Adrian says:

      Jake – there have been many problems like this in the past, where the LDF’s of the much larger, but non-polar CCl4 molecules, outweigh the LDF’s and dipole-dipole IMF’s of the much smaller, but polar, HCl.

      • Adrian, between this comment and the kid annoyed by the buffer, makes you wonder about the % of AP chemistry teachers that apparently have no idea about what is tested doesn’t it? Both this questions where LDFs dominate and acid/base buffers are on the exam every year. As you have said repeatedly there are some kids not prepared to even take AP Chem, but there are also some % that are prepared and just have teachers that don’t know what is tested, which is a shame.

        • Adrian Adrian says:

          My thoughts exactly.

          • The IMF one was easy af. All you had to do was talk about the different IMFs and explain which one is stronger and how that affects the vapor pressure. I knew there was no hydrogen bonding because there was no F,N, or O.

            But the buffer one was so dumb. It should be dropped so I can get a 5 on the stupid exam.

          • Oh and I talked about how in one of them the dipole moments cancel out and they dont in the other (Idk if thats right tho but it was kind of after I explained everything so it wasn’t my main argument).

            My prediction:

            56/60 MC
            9/10 Q1
            9/10 Q2
            2/10 Q3
            4/4 Q4
            3/4 Q5
            3/4 Q6
            4/4 Q7

          • Adrian Adrian says:

            Well Joseph, that would be a score of approx. 81/100, and the highest score that we’ve seen needed for a 5 on the new exam has been 79. Check back in July when you get your score, I’d love to know what you got!

          • If that’s true I’ll be fine. But when you only get 2 points on a 10 point question, I wouldn’t consider that great. And that’s on the assumption those are what I got for the other Free responses and MC (though I’m sure there is no way I got less than 53 on the MC)

  14. Hi Adrian, a quick question regarding 1b(ii), the graph which you sketched crossed the activation energy line, however, it mentioned in the question that no is observed to occur. So can you explain to me how you approached the problem? Thanks.

    • Adrian Adrian says:

      Josh, I’ll quote Paul C., and his comment below. The prompt says “no reaction is OBSERVED to occur.” That does not mean that there are no collisions with sufficient energy, just that there are too few to produce an observable reaction.

  15. Fkn hell. I’m retaking the Chem exam next year and actually going to study buffers this time. Freaking retarded question.

  16. 43arcsec says:

    3d

    I might be reading something wrong here, but student one made a buffer by our calculating the amount of NaOH to put in, and we put in only enough to get us to half equilibrium point. The second student put in enough NaOH to get us to the equilibrium point (the # of moles of NaOH, .1moles, was the same as the HNO2, .1litersx1M=.1moles). So the 2nd student’s mixture has no buffering capacity at all. Sorry if I missed something here, but maybe you can set me straight. Thanks.

  17. Wantedtoknow@me.com says:

    If I got around a 33/46 on the FRQs, how likely is it that I got a 5 on this year’s chemistry test?

    • Adrian Adrian says:

      It depends on (a), what you got on the MCQ’s, and (b), what the grade boundaries are. We all know the grade boundaries are virtually impossible to predict, but assuming that your performace on the MCQ’s matched your FRQ performance, then you would have a score of 72. That would almost certainly be a 4, maybe a 5, depending on where grade boundaries are drawn. Please note that this is pure speculation on my part!

      • Wantedtoknow@me.com says:

        I am almost certain I got around a 90%, definitely no lower than an 80% on MC. Anyway, thanks for the reply… I just really hope I end up getting a 5 though since the mistakes I made on the FRQs were really dumb tbh. 😓

        • Dude, the 2014, 15, and 16 MC were very easy. Idk why the Collegeboard decided to put an even easier set of MC that a 2 year old could do on the 2017 exam lol. But I guess they balanced it out with the buffer question on the FRQ.

          Btw, I wouldn’t be surprised if I got 58+/60 on MC.

          • Wantedtoknow@me.com says:

            I am just being safe……… there are only 1-2 on the entire thing that I guessed on, and about 6 answered when going through a 2nd time. I am factoring in for an occasional dumb mistake.

  18. http://appass.com/calculators/chemistry?curve=2015

    Is this accurate? Because according to this, I easily got a 5.

    • Wantedtoknow@me.com says:

      Look at 2016- the curve varies.

      • even w/ the 2016 curve, I get a 5. Tho its kind of confusing cause the max is 50 MC questions.
        But I’m worried cause Dingle told me the curve was 79/100 for a 5 on the 2015 exam.
        I am projecting an 81/100 so that’s like borderline.

        • Wantedtoknow@me.com says:

          only 50 questions count on the MC, 10 are field questions. He probably misspoke though, since 69/100 was the curve for a 5 on the 2015 exam. You’ll be fine and I probably will too, as I kind of feel like I will get around an 80% as well.

          • I’m retaking the exam next year if I don’t get a 5. It was so fkn stupid how they threw me off with a buffer problem. But regardless, i need to study for my Calc exam on Tuesday but it’s hard cause I can’t stop thinking about how one problem could ruin my reputation.

          • I just can’t get it off my mind cause the concept seems so simple in retrospect (literally would’ve taken me 10 minutes to learn if my teacher taught me it instead of tossing us the Henderson hasselbach eqution and letting us try to apply it). I’ve taken 4 AP exams so far this year (10 throughout my high school career) and this is the only one I possibly got lower than a 5 on cause of the fkn buffer question.

        • Adrian Adrian says:

          “cause Dingle told me the curve was 79/100 for a 5 on the 2015 exam.”

          No I didn’t. I said, “On a recently administered new exam, it was 79”. That was NOT the 2015 Operational Exam. The 2015 grade boundaries were not released.

  19. Wantedtoknow@me.com says:

    How hard would you say this is compared to the Chemistry Subject test?

    • AP is ‘harder’, but two caveats. There are several things on the SAT that are not on the AP, and secondly, don’t think that preparing for one is the same as preparing for the other – it isn’t. Different question types, emphasis and approaches required etc.

  20. For the MC, are all 60 graded or just 50? If its just 50, is your score scaled down or do the 10 just not matter? I only ask because some score calculators have 50 questions and some have 60. If I estimate that I got 50/60 right on the MC, what would my x/50 be?

    • Not sure Danny, but I am looking into it for you. I suspect that they remove the unknown 10, and report the score out of the other 50 but I am not certain. I am checking right now.

    • Ignore the 10 statistical questions, and grade the remainder out of 50.

      • so 10 of the questions are just for statistical purposes?

        • Then I definitely banked the money. For sure. 50/50 for sure. Got the money (If they drop the buffer question). For sure. I literally only didn’t know like 2 of the MC. The rest were V-E-R-Y Ęæzy — like easy enough to the point where I know I got them right. Like I can’t stress that enough. And if those 2 I didn’t know are part of the “statistical” questions, I definitely banked the money. #GotTheW #screwbuffers #dropthebufferquestioncausenooneknewwhatthehellitwassaying

          • All I need is closure on the damn buffer problem. It’s eating me alive knowing I got only 2 points on it. But I’m hoping I nailed the rest of the FRQs.

  21. 43arcsec says:

    Does anyone know if the late AP Chem exam given today, May 18th, will be posted anywhere?

    Thank you

  22. For 3d, is it correct to say that in the second solution, since there are equal concentrations of the conjugate base and acid, then the second buffer is more resistant to pH changes?

    • Well, it can absorb more with more of each component, but…..

      • Thank you for posting your answers, Adrian. For 1bii, if I shifted the graph to the right, but did not decrease the height of the curve, would I be marked off?

      • I would not accept that answer to 3d, and don’t expect that it will be accepted. ( I will let you know soon!) Resistance to pH change depends on quantity, not concentration. I would also expect that the peak of the lower temperature graph would have to be higher than that of the higher temperature graph to get the point.

  23. If you were to grade this exam, would you accept that answer to 3d? Also, for 1bii, if I shifted the graph to the right, but did not decrease the height of the curve, would I be marked off?

    • It depends on how they interpret the words, “resistant to changes in pH”, that’s why I wrote two different paragraphs for that answer. Only time will tell. As for the graph, the peak has to be to the left for the lower temperature.

  24. Dingle — Is the SAT Chem Subject exam similar to the AP Chem exam? I’m planning to take it and just want to know if there’s anything additional I would need to learn or if I’m fine as is (from knowing the AP content). Thanks.

    • Many differences, see; https://www.adriandingleschemistrypages.com/sat/sat-subject-test-chemistry-2016/ and look at the ‘Content & Preparation section.

      • What does “many differences” mean? It’s chemistry. Is it like the way the question is asked that is different or additional content?

        • Joseph – Let’s get one thing straight – the inclusion of buffers on the AP chemistry exam, including an entire question, is absolutely fair and a crucial component of the AP chemistry curriculum. The ranting and raving that you have done on this forum about the buffer question simply shows one thing – your teacher didn’t adequately prepare for the test. You very well may still get a 5 on the test but to call the buffer question BS and talk about it being removed just shows that your were not prepared to answer a buffer question. Anyone that knows the content of AP chem should ABSOLUTELY know that the question was not out of the realm of the ap chemistry curriculum and be able to answer it without much difficulty.

          • I already gave my teacher an earful. She’s to blame as well.

            However, I got caught off guard by the question. No one explained to me buffers in the way the AP exam required. All I knew was the Henderson Hasselbach sh*t and some other small concepts related to buffers.

            Also, all the past AP exams since 2013 didn’t have “full” buffer questions so there’s that. They had minor ones that I could have easily solved. Regardless, I think I’m getting borderline 5 (based off what Dingle has said). If I fall short, I’m retaking it next year.

  25. Mr. Dingle, I just saw on your twitter page that you finished the AP Chem readings and have the average score per question. Idk if you’re allowed to tell but if you can, can you tell me the average score for #3? Please.

  26. For the Lewis diagram in question 1c, would a triple bond between the sulfur atoms, each with one lone pair and single bonds between Cl and S atoms with three lone pairs around each Cl be accepted. The formal charge is still 0 on all of the atoms involved.

  27. Wantedtoknow@me.com says:

    Wantedtoknow@me.com

    Ended up getting a 5!

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