AP Chemistry 2024 Free Response Question #2 - SOLVED!

[@jaredflores-melo3045]

this one was light

[@unknowngamer6831]

For part C, I didnt do any math (it didnt say solve anyhring) I just said that since the left one stayed the same and the NaHCO3 increased, and more was produced, then it was the LR

[@giannas3204]

Same

[@lukasdire3269]

funny enough me too

[@ganshyammaharaj1]

i second guessed myself for so many of them when they were correct and i hate myself for that

[@marieheartfilia6766]

SAME

[@Na0811te]

Would a non math analysis with a written explanation work for part c? I explained that since mass (therefore mols) of H2C4H2O4 stayed constant and the mass of NaHCO3 increased and our moles of product increased that the NaHCO3 was the LR. I then clarified that if H2C4H2O4 was the LR, then the moles of our product wouldn’t have increased when NaHCO3’s mass was increased.

[@Chen-rz2tg]

yes I’m pretty sure you get full points for it

[@Na0811te]

@@Chen-rz2tg I hope so, I could use every point possible I just want a 3

[@kakai2164]

did the same thing, hopefully we do (justifys are normally word answers anyways)

[@amyhammer4961]

When I worked through this problem, my first thought was to do the math, but I wanted to use both sets of data so I answered the same way you did here. "Increasing the mass of NaHCO3 from experiment 3 to 4 caused the moles of CO2 to increase. If H2C4H2O4 were the LR, the moles of product would not have changed, despite the added NaHCO3. Therefore, NaHCO3 is the LR"

[@chefethanguo9701]

@@amyhammer4961 I'm in AP Chemistry right now, and my teacher suggested me to explain it conceptually rather than with a calculation. The good news is that his explanation is literally what you mentioned here! You're all good. There was a review question that was exactly Part C in a lab packet we received in class and I wrote the equation, balanced it, and did all that, but you're all set if you used words to answer that question.

[@oniononion7560]

For part F, I rounded it to 6.1 bc of sig figs. Although now I’m just remembering that for pH/pKa you start sig figs after the decimal 😭 Would points be taken off? Bc that carried over in part G where I got a ratio of 7.99 bc 1. The log of the ratio would’ve equaled 0.9 and 2. I forgot how to solve for logs 🧍so I started guessing on my calculator till I got kinda close to my number lol

[@jotoqi8728]

I did the exact same thing

[@jotoqi8728]

I think we’re fine as long as they see our mathematical process and that it’s correct

[@josephyost22]

Yes same for whatever reason I ended up with .9=log(x)

[@josephyost22]

@@jotoqi8728the annoying thing is we will never know if they took it or not

[@andrea-bala]

Hello Mr. Krug, for (f) I put 6.1 because I thought that there were two sig figs. I then used 6.1 for the pKa2 value in (g) and got 7.9. Is this acceptable?

[@josephyost22]

I think that might’ve been what I did because I also ended up with 7.9. If they did take points off it would have had to be on F and then full credit for G because they wouldn’t take extra off for a mistake on a prior problem. I think we got full credit come to think of it. 2 sig figs given so our answers had 2 sig figs and then we used that.

[@nicholasnguyen5941]

I think I got a 3 😭

[@natashaastudillo6265]

I think I got a 1

[@keshkeeper14]

I believe I got a sub zero score

[@bibou3102]

@@keshkeeper14real

[@f1kayo]

i think i got a 2 😔

[@northdakotafacts]

For part G would it be considered a carry through error if I calculated the pKA wrong in E, and used that value, but did the rest of the equation right?

[@josephyost22]

Yes as in you lose the initial points but not points later

[@ricky2972]

For Part C, I did the same work but was wondering if the question meant to look at the data table where H2C4H2O4 was constant and the NaHCO3 was incremented which resulted in an increase in moles of CO2, therefore showing that the reaction was dependent on the mass of NaHCO3 causing that to be the limiting reactant. I wrote that because it said "Based on student's data"

[@jaimilk420]

i ddi that too hope i get the point it was kinda like a logic one 😭

[@faber5573]

I said that as well I didn't even think about solving it numerically

[@devangdoshi2000]

For part D, if we said there are more particles in the products, and entropy increases with greater number of products, is that correct?

[@JeremyKrug]

I think that would work. I'm thinking they want students to mention something about the gas molecules produced, but we'll see when they release the official key.

[@JonahStone-ok3go]

hey jeremy, for f aren’t we finding the pka for the first equation, not the second?

[@JeremyKrug]

The question asks for the pKa2, which would be for the second equation.

[@CharlesIanOcampo]

for b) ii. will I still get the point if I said less than because they require less energy to dissolve the solid compared to experiment 1?

[@ZivoTBG]

Do you think a ratio of 9/1 for part (g) is okay? I somehow forgot how to get rid of a logarithm so I was plugging in values and the 9/1 got me very very close to a pH of 7

[@huyho6952]

i think you gonna get 1 point off for wrong sigfigs because 8.5 rounded to 1 sigfig is 9

[@huyho6952]

or you may get full credit cause some scoring guidelines i see sigfigs point but some i dont

[@Chen-rz2tg]

usually they only check one problem for sig figs. this question will likely be the one checked, but if not you’ll get full points

[@winllyhuang9537]

THATS SO REAL I LITERALLY FORGOT HOW TO ANTI LOG SO I WAS PLUGGING IN VALUES FOR 2 MINS 😭 it’s literally just 2nd then log button

[@chefethanguo9701]

@@winllyhuang9537 You can also use the properties of logarithms and rewrite the equation exponentially.

[@souffle713]

ik i did not just put in the surface area decreases

[@arijam0]

i didnt get this form..?

[@anniejohnson3192]

i literally forgot to convert to kelvin

[@DragonEmperor_7]

Hello Mr. Krug. I have a question on part G. For the answer, I think I put 8 instead of 8.5. I think I won’t get credit for this but please let me know if I will. Thank you

[@williamchoi6561]

Ahhh my sig figs, I put 8 too, noooooo

[@DragonEmperor_7]

@@williamchoi6561 Yeah for the ratio I put 8/1 I’m not sure if that’s right though

[@JeremyKrug]

I think you'll still get credit as long as you showed your work. They normally give you a tolerance of + or - 1 sig fig.

[@josephyost22]

@@JeremyKrugI said 7.9 with maybe some decimal places because I rounded .93 to .9 will that be too far out?

[@josephyost22]

On part G I for whatever reason rounded .93 to .9 so my answer was around 7.9. is this too much variation?

[@JeremyKrug]

This might be ok, but it depends on how CB decides to grade it.

[@RomitMakar]

How many points do I lose if I miss the last two questions only the pKa anf the acid concentration ratio q (2 or 3?)

[@Chen-rz2tg]

3, the ratio question likely had 2 points

[@tank2879]

Hi Jeremy! I don't know if you recall my username from a few days ago but I think you got me a 5 on my exam!

[@JeremyKrug]

Yes I do, and thanks for commenting! I hope you get that 5!

[@YouforiaReal]

was there different FRQ forms? cause I did NOT have any of these questions

[@NatalieTheTree]

Yes

[@dolphin601]

I also didn't get any of these. Are you an international student?

[@YouforiaReal]

@@dolphin601 no, but i remember a question on reading a buret

[@delizeka912]

@@YouforiaReal yeah me too,i took the exam in turkey btw

[@ayreauna4279]

Why did I lowkey cook. I think we’re getting that 3 guys.

[@rohilpat]

i only did two sig figs for part f...will that still land the point cuz that makes g a little off

[@Chen-rz2tg]

yes you will likely still get all points

[@williamhutton1752]

technically that's only 1 sig fig, but it depends on which question College Board decides to check for sig figs

[@anshchawla2698]

I got a different exam paper. Is the exam paper same for everyone?????

[@dolphin601]

Are you an international student because i am and my test wasn't like this.

[@anshchawla2698]

@@dolphin601 yes I am from India

[@bobdapenguin5388]

I had no clue what to do for F and G so I wrote a joke: what did the molecular compound say to the ionic compound? Don’t get salty with me!

[@Christian_Mathis_Golf_75]

Honestly I did way better than I thought

[@jeremyj4919]

Soooooooo… I’m cooked 💀

[@edvantagetv]

Nice

[@STM7878]

still on track for a 5 🙏

[@Kevin-kl8jm]

what is on track for a 5? I got 7/10 on first frq, 8/10 second, and 9/10 on third and prolly 45 on mcqs

[@commanderrei9316]

@@Kevin-kl8jmif you got a 2/4 for the rest of the part 2 questions, you’ll be at a 5 assuming u got 45 on mcq

[@Kevin-kl8jm]

@@commanderrei9316 so just half of frqs 4-7 is all I need?

[@commanderrei9316]

@@Kevin-kl8jm Yep

[@spencertopsy3855]

i dont even take ap chem but im the first one here

[@luigi3913]

i got cooked on the frq so bad

[@vindery3424]

Jeremy save me 💔💔💔

[@domestictomato]

my goat

[@blablabla-jn5ue]

I cooked on this wait wtf

[@ericfromreallife3058]

I cooked

[@lantrnv]

i failed 😂😂