I took the 2014 exam and got a 40/50 and then took the Princeton 2017 exam and did the first 50 questions and got a 32. Is the Princeton harder or was it just harder for me? Also, assuming I get 30-35 right on the FRQ, can I get a 5?
Are there any specific, more difficult/not obvious chemical equations we should be familiar with? How about laboratory guidelines and procedures?
Does anybody know why we choose an indicator with a pKa closest to the pH at the equivalence point? On question 3D of the 2015 FRQ’s, the pH at the equivalence point of the titration is about 2.5. Yet the best indicator is thymol blue, which has a pKa of 2.0. I understand that at the half-equivalence point, pH=pKA, but why does this hold valid for the equivalence point? Or do I have it all wrong?
and in pH = pKa + log [A-]/[HA], what is the ratio of A- and HA at the eq point? This one question is bugging me so muchh
The whole point of an indicator is to determine where the equivalence point is. This works because near the equivalence point, the pH of the mixtures increases/decreases quickly (refer to titration graphs). An indicator, being a weak acid/base will change color when [HIn]=[In-], where HIn and In- have different colors. Thus, using the formula Ka = [H+][HIn]/[In-], at the point where the indicator changes color (half-equiv. point), Ka = [H+] and pKa = pH. Note that this equivalence point of the indicator has nothing to do with the half-equivalence point of the overall titration. Now, if you choose an indicator with a pKa around the pH at the titration’s equivalence point, you will be able to see a color change and thus have a good idea of the amount of titrant required.
As for pH=pKa + log [A-]/[HA], you won’t be able to use it past the equivalence point since it is only applicable for the buffer region. I’m not exactly sure why, but it has something to do with assumptions made in its derivation. Instead, to calculate the pH at and past the equivalence point, you’ll have to use Kb and an ICE table to determine equilibrium concentrations. However, also note that if you’re reacting a strong base + strong acid, the pH will always be 7 at the equivalence point.
According to this AP score calculator, for 2015, around a mere 64% is enough for a 5. but for 2016, its up to 84% wat
I’m getting worried
http://appass.com/calculators/chemistry?curve=2015
Same I took the 2016 International practice test.Got 41/50 MC and 34/46 on frq. I needed 79 raw to get a five.Nearly impossible. Maybe since it was international it had a much harder curve? Only thing i’m banking on at this point.
I believe they made the curve much harder in 2016 onwards, and there is not a harder curve for internationals. In the past, a lot more people got 5s but not anymore 
I think it just varies each year. Because there were 50 MC questions last year, and the year before 60. However, there were still more 5s last year than in 2015. So it really just depends. I think you have to get about >75% to get a 5 according to calculators I have looked at.
Hey all; are we allowed to use whatever writing utensil on the FRQs? Like a black gel ink pen?
I read in the AP student bulletin that you need to use a pen, but you can strike through the part you don’t want to be graded.
Does anyone know if significant figures are important on the free response?
Are Barron’s AP Chem Practice tests similar to the actual multiple choice questions??
Significant figures are important on the frq’s, you can lose up to one point per problem for not having the correct number of significant figures in an answer in that problem.
@Tobster18 The test tomorrow will have 60 questions. Collegeboard throw out 10 questions that’s why it has 50.
@Soccer1235 Yea the curve went from 72/100 in 2015 to 79/100 
If I would have known the curve is so harsh I wouldn’t have put all this time into attempting a five.
Yeah man, anyone know the curve for a pass? I’ve been working my butt off the whole year and I just want to pass the test.
Given all this talk about a less forgiving curve, how many questions could one miss on the MC and do ok on the FRQs to get a 5?
@logosoverpathosm Lets say I get 40/50 MC and 8-8-8-3-3-3-3 my raw (MC + 1.0869(FRQ SCORE))=79.13
79-100 is a five so that’s the BARE minimum needed for a 5.
There is no way you need a raw score of 79 to get a 5… from what I’ve heard its more near the 70% range, if I need 79 as a raw score, I will get a 4, then I will kill myself.
lol yeah the curve can’t be 79 for a 5, that’s ridiculous. It’s about 72-75, and one year it was even 68.