AP Chemistry Question of the Day





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Discus: SAT/ACT Tests and Test Preparation: May 2003 Archive: AP Chemistry Question of the Day
By Heatwave345 (Heatwave345) on Saturday, April 26, 2003 - 12:22 pm: Edit

Hopefully, this thread will help us on the AP Chemistry test.

Bromide, Cloride, and Iodide ions all precipitate with what cations. (there's three of them)

By Pat57575 (Pat57575) on Saturday, April 26, 2003 - 12:42 pm: Edit

I've been outta chem for a year, but I'm guessing silver, lead, and...umm... maybe mercury or barium?

By Jason817 (Jason817) on Saturday, April 26, 2003 - 01:08 pm: Edit

Great thread!

Answer: Ag+, Pb2+, and Hg2 2+

I have some questions from the 1994 Multiple Choice exam that I need help on. I know the answers but dont know why:

34.

X = CH3-CH2-CH2-CH2-CH3

Y = CH3-CH2-CH2-CH2-OH

Z = HO-CH2-CH2-CH2-OH

Based on concepts of polarity and hydrogen bonding, which of the following sequences correctly lists the compounds above in the order of their increasing solubility in water?

(A) Z < Y < X
(B) Y < Z < X
(C) Y < X < Z
(D) X < Z < Y
(E) X < Y < Z


38. Concentrations of colored substances are commonly measured by means of a spectrophotometer. Which of the following would ensure that correct values are obtained for the measured absorbance?

I. There must be enough sample in the tube to cover the entire light path.
II. The instrument must be periodically reset using a standard.
III. The solution must be saturated.

(A) I only
(B) II only
(C) I and II only
(D) II and III only
(E) I, II, and III


39. Samples of F2 gas and Xe gas are mixed in a container of fixed volume. The initial partial pressure of the F2 gas is 8.0 atmospheres and that of the Xe gas is 1.7 atmospheres. When all of the Xe gas reacted, forming a solid compound, the pressure of the unreacted F2 gas was 4.6 atmospheres. The temperature remained constant. What is the formula of the compound?

(A) XeF
(B) XeF3
(C) XeF4
(D) XeF6
(E) XeF8


Theres more but I'll post them later. Thank you.

By Jumbo (Jumbo) on Saturday, April 26, 2003 - 01:43 pm: Edit

I remember all these questions but I only remember the answer to the first two. for #1, the reason why is because of the polarity within the molecules. X has no variation cuz its all single bonds. Y is polar b/c of the OH, and Z is even more so cuz it has 2 OH's. Like dissolves like, so the more polar a molecule is, the more likely it is to dissolve.

For the second problem, this is kind of a bio-related question. For a spectrophotometer to work, it has to be able to send light completely through someting, b/c how can you measure % transmittence if you can't record accurate data? In order to interpret the data, one must have a standard as well (a clear vial with nothing in it) so there is a comparison to be made.

By Quarky (Quarky) on Saturday, April 26, 2003 - 01:52 pm: Edit

I am not very good at chem, but I am pretty sure that question 39 is D, since xenon hexafluoride is the only compound formed by an inert gas.

By Jason817 (Jason817) on Saturday, April 26, 2003 - 02:57 pm: Edit

34 was E
38 was C
39 was C

Thanks jumbo. Quarky, you can't do it that way. Then there would be no need to solve it if you already know its hexafluoride.

By Quarky (Quarky) on Saturday, April 26, 2003 - 03:04 pm: Edit

hmm interesting

By Heatwave345 (Heatwave345) on Saturday, April 26, 2003 - 10:24 pm: Edit

39)

we know that 1.7 atm of Xe reacted

8.0 atm - 4.6 atm = 3.4 atm of F2 reacted

so the ratio of F2 reacted to Xe reacted is 2 to 1

therefore the end product is XeF4 which is C.


here's my question:

name the six strong acids with VERY LARGE Ka.

By Jason817 (Jason817) on Saturday, April 26, 2003 - 11:07 pm: Edit

H2S04, HCl, HNO3, HI, HBr, H2CO3 (not sure on this one)???

By Mew246 (Mew246) on Saturday, April 26, 2003 - 11:16 pm: Edit

HCl, HBr, HI, HClO4, HNO3, and H2SO4, I'm not sure though. Argh... need to go study more!

By Heatwave345 (Heatwave345) on Sunday, April 27, 2003 - 07:40 am: Edit

Mew is correct, H2CO3 is not a strong acid, it's perchlorate.

By Jason817 (Jason817) on Sunday, April 27, 2003 - 11:42 am: Edit

Yeah I wasnt sure on the last one. HClO4 is the one I missed

By Jason817 (Jason817) on Sunday, April 27, 2003 - 11:45 am: Edit

If there are no other questions then let's try these:

51. 4 HCl(g) + O2(g) 2 Cl2(g) + 2 H2O(g)

Equal numbers of moles of HCl and O2 in a closed system are allowed to reach equilibrium as repre sented by the equation above. Which of the following must be true at equilibrium?

I. [HCl] must be less than [Cl2].
II. [O2] must be greater than [HCl].
III. [Cl2] must equal [H2O].

(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III

52. When dilute nitric acid was added to a solution of one of the following chemicals, a gas was evolved, This gas turned a drop of limewater, Ca(OH)2, cloudy, due to the formation of a white precipitate. The chemical was

(A) household ammonia, NH3
(B) baking soda, NaHCO3
(C) table salt, NaCl
(D) epsom salts, MgSO4 . 7H2O
(E) bleach, 5% NaOCl

By Heatwave345 (Heatwave345) on Sunday, April 27, 2003 - 12:20 pm: Edit

51. I do not know how to do this question, was a Kc value given in the question?

52. (D), because Calcium sulfate is insoluble

By Sosodef (Sosodef) on Sunday, April 27, 2003 - 12:55 pm: Edit

51. I am guessing it is c

52. i am guessing D

By Jason817 (Jason817) on Sunday, April 27, 2003 - 01:30 pm: Edit

None of you are correct in either question. There was no Kc value given.

By Mew246 (Mew246) on Sunday, April 27, 2003 - 02:03 pm: Edit

51) Not sure
52) B

By New (New) on Sunday, April 27, 2003 - 02:31 pm: Edit

for #51
i'm not exactly sure if this is the way to do it:
set up ICE

4 HCl(g) + O2(g) 2 Cl2(g) + 2 H2O(g)
I |x | x | 0 | 0
C |-4y | -y | +2y | +2y
E |x-4y | x-y | 2y | 2y

as you can see:
you can't tell if [HCl] > [Cl2]
but, since O2 only decreased by y, [O2] > [HCl]
and, [Cl2]= [H2O] = [2y]
so it's (D)

By Heatwave345 (Heatwave345) on Sunday, April 27, 2003 - 03:29 pm: Edit

Jason

what are the correct anwsers?

By Jason817 (Jason817) on Sunday, April 27, 2003 - 04:14 pm: Edit

Answers:
51. D
52. B

Mew: Can you explain how you got 52??

By Mew246 (Mew246) on Sunday, April 27, 2003 - 04:38 pm: Edit

I thought it was B for 52 because the HNO3 and NaHCO3 leads to NaNO3 and H2CO3 (g), then if H2CO3 goes with the Ca(OH)2 the CaCO3 would precipitate and H2O would be formed.
(I'm not sure if im entirely right though) :)

By Mew246 (Mew246) on Sunday, April 27, 2003 - 05:07 pm: Edit

I got a question, might be a bit easy though:

47. WHich of the following is not a complex ion?
A)Cr2O7 2-
B) Ag(NH3)2 1+
C) FeCl6 3-
D) Cd(CN)4 2-
E) HgI4 2-

Actually im 99% sure about number 52 now

By Jason817 (Jason817) on Sunday, April 27, 2003 - 05:58 pm: Edit

A

By New (New) on Sunday, April 27, 2003 - 10:50 pm: Edit

how can you tell a complex ion from one that's not? (sorrie newbie here)

By Jason817 (Jason817) on Sunday, April 27, 2003 - 11:13 pm: Edit

You would have to have learned what a complex ion is. Go here:

http://www.chemguide.co.uk/inorganic/complexmenu.html

By New (New) on Sunday, April 27, 2003 - 11:36 pm: Edit

thanx jason!

By Heatwave345 (Heatwave345) on Monday, April 28, 2003 - 07:30 pm: Edit

here's another question:

Calculate the mass of aluminum produced in 1.00 hour by the electrolysis of molten AlCl3 if the electrical current is 10.0 amperes.

HINT!!!
Amperes = Coulumbs/Second

By Heatwave345 (Heatwave345) on Monday, April 28, 2003 - 09:09 pm: Edit

i have another question...

are you allowed to use the periodic table fo the entire test?

By Dxiw (Dxiw) on Monday, April 28, 2003 - 09:31 pm: Edit

yes, but no calc or formulas on mult chioce, the free response has full formula sheets and calculator..

By Jason817 (Jason817) on Monday, April 28, 2003 - 09:46 pm: Edit

u can use a periodic table on the entire test.

Is the answer 3.35 grams (i did my work on paper)? Just learned that in class today...

If i am right, I will post how i did it.

By Heatwave345 (Heatwave345) on Tuesday, April 29, 2003 - 06:28 am: Edit

yes, the answer is 3.35 grams

By 9331 (9331) on Tuesday, April 29, 2003 - 03:47 pm: Edit

What section is this on? My class just finished a chapter on acids and base. Are we reallly behind?

By Heatwave345 (Heatwave345) on Tuesday, April 29, 2003 - 04:02 pm: Edit

it should be in the electrochemistry unit

By Jason817 (Jason817) on Tuesday, April 29, 2003 - 05:32 pm: Edit

yeah you are behind...catch up with Barrons AP Chem Book. You should be on Electrochemistry, which is what we are on. But we havent done 4 of the labs so we are behind too.

By Jason817 (Jason817) on Tuesday, April 29, 2003 - 05:32 pm: Edit

yeah you are behind...catch up with Barrons AP Chem Book. You should be on Electrochemistry, which is what we are on. But we havent done 4 of the labs so we are behind too.

By Heatwave345 (Heatwave345) on Tuesday, April 29, 2003 - 07:36 pm: Edit

I really really really really really dislike the Barron's AP Chemistry book, it is extremely hard!!! IMO

By Jason817 (Jason817) on Tuesday, April 29, 2003 - 08:44 pm: Edit

yeah it is but it is the only book I know of that covers everything. PR covers too little, and textbooks aren't good for reviewing.

By 9331 (9331) on Wednesday, April 30, 2003 - 03:18 pm: Edit

This is my teacher's second year teaching, she doesn't know how to do it just yet. I have both the Barron and the PR book and am trying to review as much as I can. There is sooo much to do.

Another quick question, how many labs have your class completed this year? We've only done 3.

By Heatwave345 (Heatwave345) on Wednesday, April 30, 2003 - 05:07 pm: Edit

around 5. the school took away all radioactive materials :(

By Jason817 (Jason817) on Wednesday, April 30, 2003 - 07:12 pm: Edit

We did 4. AP curriculum requires 7 or 8. So basically, my class is screwed on the free response lab section on the exam.

Next questions:

56. It is suggested that SO2 (molar mass 64 grams), which contributes to acid rain, could be removed from a stream of waste gases by bubbling the gases through 0.25-molar KOH, thereby producing K2SO3. What is the maximum mass of SO2 that could be removed by 1,000. liters of the KOH solution?

(A) 4.0 kg
(B) 8.0 kg
(C) 16 kg
(D) 20. kg
(E) 40. kg


59. When a 1.00-gram sample of limestone was dissolved in acid, 0.38 gram of CO2 was generated. If the rock contained no carbonate other than CaCO3, what was the percent of CaCO3 by mass in the limestone?

(A) 17%
(B) 51%
(C) 64%
(D) 86%
(E) 100%


64. At 25 degrees celsius, a sample of NH3 (molar mass 17 grams) effuses at the rate of 0.050 mole per minute. Under the same conditions, which of the following gases effuses at approximately one-half that rate?

(A) O2 (molar mass 32 grams)
(B) He2 (molar mass 4.0 grams)
(C) CO2 (molar mass 44 grams)
(D) Cl2 (molar mass 71 grams)
(E) CH4 (molar mass 16 grams)

By Mew246 (Mew246) on Wednesday, April 30, 2003 - 07:15 pm: Edit

anyone know where i can get real sat ii chem tests? thanks

By Pat57575 (Pat57575) on Wednesday, April 30, 2003 - 07:55 pm: Edit

These are the answers I got.
56. B
59. D
64. D
Are they correct?

By Jason817 (Jason817) on Wednesday, April 30, 2003 - 08:22 pm: Edit

you cant find real sat II chem tests online. The ones I have are real AP tests. Real SAT II's can only be gotton from the Real SAT II book.

Pat: Yes those are the answers. How did you get those?

By Mew246 (Mew246) on Wednesday, April 30, 2003 - 09:20 pm: Edit

The ones in the Reat SAT II Book are soo old, is there anyway I can get newer ones, more recent? Oh yeah, Jason your right about the question i posted. If i have time ill try to post some good/hard questions. :)

By Jason817 (Jason817) on Wednesday, April 30, 2003 - 09:51 pm: Edit

there are no other tests. College Board is making a new edition of Real SAT II but thats being released later this year is it probably would not help you.

As for the questions, they are just really easy. On a practice multiple choice AP test, I get about half right so I'll be lucky to get a 3, hopefully a 4.

By Pat57575 (Pat57575) on Wednesday, April 30, 2003 - 11:51 pm: Edit

Jason817- Good luck on your upcoming chem test!
As for the solutions...

56)

First setup your equation.

SO2 + 2KOH --> K2SO3 + H2O

From here it is all stoichimetrics.

(1000L sol)(.25 mol KOH/sol)(mol SO2/2 mol KOH)(64.1 g SO2/mol SO2) = 8013 g SO2

59)

Once again, set up your general equation:

2CaCO3 --> 2Ca + 2CO2 + O2

(.38 g CO2)(mol CO2/44g CO2)(2 mol CaCO3/2 mol CO2)(100.1 g CaCO3/mol CaCO3) = .865 g CaCO3

%m = mass CaCO3/total mass * 100%
= .865/1 * 100%
= 86.5%

64)

For this one, you have to know your general 'rate of effusion law':

rate1/rate2 = (M2/M1)^(1/2)

where M1 and M2 are the molar masses of the respective gases

From here it's a plug in.

rate1/(.5*rate1) = (M2/17)^(1/2)

(1/.5)^2 = M2/17
M2 = 17*4
M2 = 68 g/mol

Our closest choice is Cl2, which has a molar mass of 71 g/mol.

By New (New) on Thursday, May 01, 2003 - 01:01 am: Edit

here are two: (1999 mc)
64) Equal number of moles of He(g), Ar(g), and Ne(g) are placed in a glass vessel at room temperature. If the vessel has a pinhole-sized leak, which of the following will be true regarding the relative values of partial pressures of the gases remaining in the vessel after some of the gas mixture has effused?
a) P(He) < P(Ne) < P(Ar)
b) P(He) < P(Ar) < P(Ne)
c) P(Ne) < P(Ar) < P(He)
d) P(Ar) < P(He) < P(Ne)
e) P(He) = P(Ar) = P(Ne)

65) Which of the following compounds is not appreciable soluble in water but is soluble in dilute hydrochloric acid?
a) Mg(OH)2 (s)
b) (NH4)2CO3 (s)
c) CuSO4 (s)
d) (NH4)2SO4 (s)
e) Sr(NO3)2 (s)

By New (New) on Thursday, May 01, 2003 - 01:05 am: Edit

I was wondering where I can find additional MC's online or elsewhere (other than the 1999 MC). The AP chem in our school just started... teacher doesn't know anything yet; no past exam, nothing. Where can i find additional problems to practice?
Anyone can help?

By Jason817 (Jason817) on Thursday, May 01, 2003 - 02:21 am: Edit

Crap load of practice exams:
http://www.mhs.k12.oh.us/apchemtests/
(this is where I am getting these MC's)


Pat: If you don't mind me asking, do you have a degree in chemistry or are you just really really good?

By Heatwave345 (Heatwave345) on Thursday, May 01, 2003 - 07:59 pm: Edit

1) A
2) A

are those right, i post how i did them if i get conformation.

By Jason817 (Jason817) on Thursday, May 01, 2003 - 11:15 pm: Edit

I would say
1. A
2. A

answers:
A
A

both right.

By Pat57575 (Pat57575) on Friday, May 02, 2003 - 07:04 pm: Edit

Jason: Thanks for your praise. However, when it comes down to it, I'm just a high school kid that does pretty well in chem and physics :)

By Mew246 (Mew246) on Saturday, May 03, 2003 - 11:00 am: Edit

If i can get 50 to 60 mc questions right, how what kind of score may i get?

By Heatwave345 (Heatwave345) on Saturday, May 03, 2003 - 11:03 am: Edit

5 or 4 (most likely 5) depending on how ou do in the free response

By Mew246 (Mew246) on Saturday, May 03, 2003 - 11:42 am: Edit

thats good i better study hard for those open responses, thanks.

By New (New) on Saturday, May 03, 2003 - 08:36 pm: Edit

let's keep it going:

29. When an aqueous solution of NaOH is added to an aqueous solution of potassium dichromate, K2Cr2O7 the dichromate ion is converted to
(A) CrO42¯
(B) CrO2
(C) Cr3+
(D) Cr2O3(s)
(E) Cr(OH)3(s)

74. A solution of calcium hypochlorite, a common additive to swimming-pool water, is
(A) basic because of the hydrolysis of the OCl¯ ion
(B) basic because Ca(OH)2 is a weak and insoluble base
(C) neutral if the concentration is kept below 0.1 molar
(D) acidic because of the hydrolysis of the Ca2+ ions
(E) acidic because the acid HOCl is formed

75. A direct-current power supply of low voltage (less than 10 volts) has lost the markings that indicate which output terminal is positive and which is negative. A chemist suggests that the power supply terminals be connected to a pair of platinum electrodes that dip into 0.1-molar KI solution. Which of the following correctly identifies the polarities of the power supply terminals?
(A) A gas will be evolved only at the positive electrode.
(B) A gas will be evolved only at the negative electrode.
(C) A brown color will appear in the solution near the negative electrode.
(D) A metal will be deposited on the positive electrode.
(E) None of the methods above will identify the polarities of the power supply terminals.

By Heatwave345 (Heatwave345) on Sunday, May 04, 2003 - 03:41 pm: Edit

29. A

30. A

31. no idea

By New (New) on Monday, May 05, 2003 - 12:52 am: Edit

These ones are interesting: (1995 oe)
7) Explain the following in terms of the electronic structure and bonding of the compounds considered.

(a) Liquid oxygen is attracted to a strong magnet, whereas liquid nitrogen is not.

(b) The SO2 molecule has a dipole moment, whereas the CO2 molecule has no dipole moment. Include the Lewis (electron-dot) structures in your explanation.

(c) Halides of cobalt(II) are colored, whereas halides of zinc(II) are colorless.

(d) A crystal of high purity silicon is a poor conductor of electricity; however, the conductivity increases when a small amount of arsenic is incorporated (doped) into the crystal.

By Muawan (Muawan) on Monday, May 05, 2003 - 07:25 pm: Edit

74. A. OCl- is the conjugate base of a weak acid.
so it forms basic salts.
75. B. Reduction Takes Place at the Cathode. K will nto be reduced, by H2O will. H2 will form at the cathode. Since electrons come from the negatively charged electrode, the H2 will form there.

By Muawan (Muawan) on Monday, May 05, 2003 - 07:30 pm: Edit

7.a. O is paramagnetic, while N is diamagnetic.
b. Draw the lewis diagrams and its clear.
c. Cobalt does not have a full d shell so there is room for the excitement of these D electrons.
d. There are holes in the Si which the Arsenic e- will fill since they ahve different #s of electrons in their valence sehlls. As the electrons move from the Si to the As, the filled Si shells move to the now empty As. So you have holes that always exist and will always be filled. Transistors work by doping Si with Ga and As.


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