[cubejunkies]

So for frq practice, my teacher had me do the 2002 form b frq, number 5 only and since he won't grade them for a while, and I really want to know how I did/the right answers/ how my responses could be better, I figured it wouldn't hurt to post my responses here.

Here's the frq itself
http://www.collegeboard.com/prod_downloads/ap/students/chemistry/b_chemistry_frq_02.pdf

a. CoCl₂ because the d orbital of the compound is not filled completely so the color is going to be different...?

 I have no idea really, the teacher just said to us all that this was it and we would cover it later on in the unit, but I want to try and understand it now. I remember sort of what d orbitals are, but I don't know how this would affect appearance.

b. AgCl because the other salts are soluble in water, and AgCl is the only one that isn't.

I only know this because I memorized a little song to remember solubility rules, and so I didn't know of anything else to put that might help back-up my answer.

c. NaNO₃ because adding this to the solution would cause a double replacement reaction to take place that would precipitate out AgNO₃ and NaCl, and AgNO₃ has a distinct color.

AgCl (s) + H₂O (l) + NaNO₃ (aq) AgNO₃(aq) + NaCl(aq) + H₂O (l)

I feel like this is my most detailed of the responses, yet it still needs some more support in some way

d. BaCl₂ because as an aqueous solution, Na₂SO₄ would dissociate to form a sulfate group that would easily react with the Barium component of BaCl₂ in aqueous solution, therefore BaSO₄ would precipitate from the solution, which would be a distinctly different color than the clear NaSO₄ only solution
 
I really don't like saying "distinctly different color" but I don't know any other way to say that the solution would be visibly different

e. NH₄Cl because in the aqueous solution of NaOH, the NH₄ would act as a weak proton donor and would not react completely with the excess of solution, so the solution would maintain equilibrium as:

NH₄Cl + NaOH NH₃ + NaCl

Furthermore, the NaCl would not react with the NaOH if it were the salt anyways.

This one seems kinda like I'm on the right track, but like I'm just short in some way

Any input would be valuable! I understand its kind of a large favor to ask, but I figured I would try anyways! Also, some leniency would be appreciated because its been only 3 weeks now in school and I've forgotten a lot of the aspects of tough concepts such as equilibrium over the summer

Thank you all so much!
Anthony

P.S. Also, seeing as I kinda tanked this one, are there any frqs you guys can suggest to me for further practice, or any aqueous solution problems in general?

[Borek]

a. CoCl₂ because the d orbital of the compound is not filled completely so the color is going to be different...?

Simply list what the color should be.

b. AgCl because the other salts are soluble in water, and AgCl is the only one that isn't.

OK

c. NaNO₃ because adding this to the solution would cause a double replacement reaction to take place that would precipitate out AgNO₃ and NaCl, and AgNO₃ has a distinct color.

AgCl (s) + H₂O (l) + NaNO₃ (aq) AgNO₃(aq) + NaCl(aq) + H₂O (l)

No. First - there will be no reaction. Second - google or check your book, what is the color of AgNO₃.

d. BaCl₂ because as an aqueous solution, Na₂SO₄ would dissociate to form a sulfate group that would easily react with the Barium component of BaCl₂ in aqueous solution, therefore BaSO₄ would precipitate from the solution, which would be a distinctly different color than the clear NaSO₄ only solution

I really don't like saying "distinctly different color" but I don't know any other way to say that the solution would be visibly different

Production of precipitate.

e. NH₄Cl because in the aqueous solution of NaOH, the NH₄ would act as a weak proton donor and would not react completely with the excess of solution, so the solution would maintain equilibrium as:

NH₄Cl + NaOH NH₃ + NaCl

Good reaction. What do you know about properties of both products?

[opti384]

P.S. Also, seeing as I kinda tanked this one, are there any frqs you guys can suggest to me for further practice, or any aqueous solution problems in general?

I strongly recommend that you tackle all the recent frqs including the form Bs if you're gonna take the AP exam.

[cubejunkies]

c. NaNO₃ because adding this to the solution would cause a double replacement reaction to take place that would precipitate out AgNO₃ and NaCl, and AgNO₃ has a distinct color.

AgCl (s) + H₂O (l) + NaNO₃ (aq) AgNO₃(aq) + NaCl(aq) + H₂O (l)

No. First - there will be no reaction. Second - google or check your book, what is the color of AgNO₃.

What should I look for? Should I look for how to predict whether a precipitate will form? And I also just realized AgNO₃ is clear lol

P.S. Also, seeing as I kinda tanked this one, are there any frqs you guys can suggest to me for further practice, or any aqueous solution problems in general?

I strongly recommend that you tackle all the recent frqs including the form Bs if you're gonna take the AP exam.

I plan on tackling them all, but its only the beginning of the year, and I want to focus on completing frqs I'll be able to actually answer for now. Any suggestions on where to find aqueous solution/ gas laws frqs? :/ I kinda don't know where to find any aside from past frqs

[opti384]

I plan on tackling them all, but its only the beginning of the year, and I want to focus on completing frqs I'll be able to actually answer for now. Any suggestions on where to find aqueous solution/ gas laws frqs? :/ I kinda don't know where to find any aside from past frqs

Why don't you order some AP prep books? They also provide some good frq practices, and of course you can practice the aqueous solution/ gas laws. 

[Borek]

c. NaNO₃ because adding this to the solution would cause a double replacement reaction to take place that would precipitate out AgNO₃ and NaCl, and AgNO₃ has a distinct color.

AgCl (s) + H₂O (l) + NaNO₃ (aq) AgNO₃(aq) + NaCl(aq) + H₂O (l)

No. First - there will be no reaction. Second - google or check your book, what is the color of AgNO₃.

What should I look for? Should I look for how to predict whether a precipitate will form? And I also just realized AgNO₃ is clear lol

You already have an insoluble salt on the left, and everything else is soluble, check solubility rules. If something doesn't dissolve, ions present in the salt are not moved into solution and can't precipitate with something else (that's not entire truth, as no salt is completely insoluble, but that's a good first approximation).

[cubejunkies]

c. NaNO₃ because adding this to the solution would cause a double replacement reaction to take place that would precipitate out AgNO₃ and NaCl, and AgNO₃ has a distinct color.

AgCl (s) + H₂O (l) + NaNO₃ (aq) AgNO₃(aq) + NaCl(aq) + H₂O (l)

No. First - there will be no reaction. Second - google or check your book, what is the color of AgNO₃.

What should I look for? Should I look for how to predict whether a precipitate will form? And I also just realized AgNO₃ is clear lol

You already have an insoluble salt on the left, and everything else is soluble, check solubility rules. If something doesn't dissolve, ions present in the salt are not moved into solution and can't precipitate with something else (that's not entire truth, as no salt is completely insoluble, but that's a good first approximation).

ohhhh I see now, thank you so much!

I plan on tackling them all, but its only the beginning of the year, and I want to focus on completing frqs I'll be able to actually answer for now. Any suggestions on where to find aqueous solution/ gas laws frqs? :/ I kinda don't know where to find any aside from past frqs

Why don't you order some AP prep books? They also provide some good frq practices, and of course you can practice the aqueous solution/ gas laws. 

Well, I was just asking if there were any online I could get aside from the college board ones, I plan on getting a review book later though