Just curious how many of you used PR to study?
@taw1020 Sorry, that’s my bad. I just opened a random periodic table. Didn’t realize I was looking at atomic number instead of mass.
The answer is ClO2- (the question is pretty far back now but maybe you still need it?)
Does anyone know if EARPLUGS are allowed on the AP? My school is so loud and I really need them? I always keep track of the time so I’d take them out with like 5 mins left so I would hear the proctor!
Could someone explain #38 on the 2014 test? Thank you.
38
At the half-equivalence point for a titration, pH = pKa of the thing being titrated.
Halve the volume of titrant added at the eq point to find the half-eq point. The pH at that point on the curve is equal to pKa.
To find the molarity of the titrant, moles of acid = moles of titrant at eq-point.
Calculate moles of acid from the given concentration and volume. Use the volume of titrant at eq-point and the moles of titrant (which is equal to moles of acid) to calculate molarity.
what kind of base is nh3, bronsted lowry or arrhenius? also can you explain why?
OK so this is to get a 5 (if you get a mediocre frq score): 44/50 MC and 6/10 on the 3 long frqs + 2/4 on the 4 short frqs.
They are allowed.
can someone explain this to me:
A solution is prepared by adding 100 mL of 1.0 M HC2H3O2(aq) to 100 mL of 1.0 M NaC2H3O2(aq). The
solution is stirred and its pH is measured to be 4.73. After 3 drops of 1.0 M HCl are added to the solution, the pH
of the solution is measured and is still 4.73. Which of the following equations represents the chemical reaction
that accounts for the fact that acid was added but there was no detectable change in pH?
(A) H3O+(aq) + OH−(aq) --> 2 H2O(l)
(B) H3O+(aq) + Cl−(aq)–> HCl(g) + H2O(l)
© H3O+(aq) + C2H3O2−(aq)–> HC2H3O2(aq) + H2O(l)
(D) H3O+(aq) + HC2H3O2(aq) --> H2C2H3O2 + H2O(l)
explanation for #11
@sonpat - Is the answer C?
its bronsted lowry because an arrhenius base gives OH-, while a bl base accepts H+
@thelinah Bronsted Lowry bases are proton recipients. NH3 becomes NH4, so it is accurate to say that they receive a proton (in the form of a hydrogen atom). Therefore, it’s definitely Bronsted Lowry.
Some bases (many) are Bronsted Lowry and Arrhenius. I’m not sure if NH3 is. An arrhenius base produces OH- in aqueous solution.
EDIT: my bad, mathman beat me to it and says it’s not an arrhenius base so that’s accurate but I’ll leave this in case the explanation of why it’s bl helps at all
Help for AP Chem FRQs, practice problems, and translated solutions can be found here https://www.youtube.com/watch?v=eOEBj8WLPRo&list=PLtjPBoq7-qeJOHd4ewJJlqVQsu9p3DtNj
Wow 99 posts since I last came here.
@glasshours yes it’s C , but I’m not sure why?
Is the 105 minute limit for the frq all at once? I heard its split up or something bc of the calculator and we cant do all 7 at the same time
@sonpat I think it’s C. The solution is a buffer, and I’m pretty sure that reaction shows how added H+ (from HCl) is neutralized. Sorry I don’t have a better explanation, but maybe someone else can add on.
A doesn’t make sense because there’s no OH to begin with and none is added, so it’s not included in a reaction.
B doesnt make sense because HCl is a strong acid so pH would increase.
D doesn’t make sense because the H would react with the C2H3O2 in a much more significant amount.
Correct me if I’m wrong anyone but I think that’s right?
Yes.
You heard wrong.