<p>For the BaSO4 question, it just wants you to know that the top row transition metals are colored, and those are the ones you should cross out.</p>
<p>HERE IS THE CURVE FOR AP CHEM</p>
<p>5 - 67 percentile which is around 107+
4 - 53
3 - 38
2 - 26
1 - lets not bother considering this score.</p>
<p>Oceanangel//
BaCl2, by colligative properties, dissociates into equimolar quantity of Ba cation so Molarity = number of moles divided by volume, and number of moles of Ba cation equals 0.1 L times 0.100 Molar = 0.01 mols.</p>
<p>Also, one mole of H2SO4 yields one mole of sulfate ion so its one to one.
we use the above formula and we have
0.1 L times 0.05 Molar = 0.005 mols</p>
<p>Now the net ionic equation:
and btw sorry ppl for the confusion w/ charges
Ba 2+ + SO4 2- –> BaSO4 (s)
i 0.01 mol 0.005 mol 0 mol
c -0.005 mol -0.005 mol +0.005 mol
e 0.005 mol I WILL NOT BOTHER THIS FOR THE SAKE OF TIME</p>
<p>and finally, Molarity = moles of Ba2+/TOTAL volume
Hence 0.005 mol / 200 mL = 0.005 mol / 0.2 L = 0.025 M
hope this helped~</p>
<p>as for the MC, can anyone tell me if the questions from 1980’s and 1990’s are harder than the 2000’s? and can anyone tell me how to calculate composite MC and FRQ scores? I want to calculate my raw scores out of 160.</p>
<p>If any of you guys haven’t seen this, then you really need to. It’s godly.</p>
<p><a href=“http://chsntech.org/review/science/chem/notes.pdf[/url]”>http://chsntech.org/review/science/chem/notes.pdf</a></p>
<p>It explains #4 for the FRQ too (page 1).</p>
<p>that has some parts where it can be possibly perceived as errors. for example, see electro chem… E cell = E red, red - E red, ox
that is, E cell = E reduction potential of reduction reaction - E reduction potential of oxidation reaction. But the sign can change when you change the definition.</p>
<p>Not trying to be greedy here, but my ap chemistry class has been such a cakewalk this year that we haven’t really even learned anything. So when I went to take a practice test in class I scored a mere 41/75 on the mc…really need to boost my score before exam day. </p>
<p>Problem is I have no practice tests (I hear only teachers have access to these, who then give them to students) to work with and few study materials. All I have is Barron’s AP Chem. 500 Flashcards…and that only reviews concepts. No real-time problems or anything in the AP-style. </p>
<p>Is anyone willing to share a couple older practice tests or share the source so I can go find them? It would be much appreciated, looking to score a 5 on this to redeem myself for a 4 on bio last year.</p>
<p>Benhpark, thanks for the explanation, but I’m still not sure why the 0.01mol of Ba2+ from BaCl2 isn’t counted in the final calculation for the concentration of Ba2+ ions…</p>
<p>And as for 1980s practice tests, I heard its much harder because they were allowed to use calculators on the MC back then</p>
<p>At @ocean</p>
<p>ok so you have 0.01 mol and 0.005 mol of Ba2+ and SO42- respectively, right?
you should realize that BaSO4 is a precipitate so that means Barium ions and sulfate ions will combine to make BaSO4, so the LR is going to be the sulfate ions which means that 0.005 moles of the barium ions will be used up, 0.01-0.005 = 0.005mol Ba2+. Now you just divide by 200 mL (0.2L) to get the final concentration.</p>
<p>I think for chem I will just review some pressure stuff and then I’m done, shouldn’t be that bad judging from the recent practice tests.</p>
<p>OHHH I get it now! haha I was looking at the two reactions as separate reactions, so I added 0.005 to 0.01 mol. Thanks you guys!!</p>
<p>prattennis_1//I can give you some tests, mail me asap at benjaminpark at iis.or.kr and I will give you 1984, 1989, 1994, 1999 and Audit for free. If you have any questions, bring them up to me quickly as well so that I can answer them for you. This is reciprocating learning. I can assure you that most of my answers would be correct cuz i am the best student in my ap chem, although there are 5 chem students, meh lol. Just boils down that im above average, but not pinpoint perfect.</p>
<p>Oceanangel//should have specified the question, i was asking if the content itself is hard for 1980’s and 1990’s MC’s.</p>
<p>Pratt, check your inbox.</p>
<p>benh, check your mail?</p>
<p>no message.</p>
<p>How about now?</p>
<p>Anyone mind sending me some practice tests too? I wanted to take one or two mor practice tests to make sure that I can get a 5 on exam day. I’ll PM my email if anyone’s willing.</p>
<p>did not receive ur message, sorry</p>
<p>If, it’s not any trouble, could someone send me some released MC too? I really have no idea what the difficulty of the MC is like, and would also like to see what I need to study more.</p>
<p>The safest and most effective emergency procedure to treat an acid splash on skin is to do
which of the following immediately?
(A) Dry the affected area with paper towels.
(B) Sprinkle the affected area with powdered Na2SO4(s).
(C) Flush the affected area with water and then with a dilute NaOH solution.
(D) Flush the affected area with water and then with a dilute NaHCO3 solution.
(E) Flush the affected area with water and then with a dilute vinegar solution.</p>
<p>I don’t understand why it’s D.</p>
<p>Appropriate uses of a visible-light spectrophotometer include which of the following?
I. Determining the concentration of a solution of Cu(NO3)2
II. Measuring the conductivity of a solution of KMnO4
III. Determining which ions are present in a solution that may contain Na+, Mg2+, Al3+
(A) I only
(B) II only
(C) III only
(D) I and II only
(E) I and III only</p>
<p>I tried wiking this one, but I don’t get how it’s A. What does a spectrophotometer measure?</p>
<p>We went over these questions in class. For the first one, our teacher said you always use a weak base to neutralize acid on your skin. You can’t use a strong base otherwise it would turn your skin into soap >.<</p>
<p>for the second question, you should have done a lab on that. It’s the one with Beer’s law where you use absorption to find the concentration of an unknown solution</p>