<p>wow- i never thought about grading scheme. </p>
<p>i've heard there's been a huge uproar about the second FR question on form A because of issues with how the test was written and multiple ways to solve the problem based on one's own interpretation of what the test was intending. have any of you heard anything about that? my ap chem teacher says that the cb will probably have to make an alternate answer key for the problem since of the huge complaints on the ap server.</p>
<p>what was wrong with #2?</p>
<p>rushbugled - you've heard correctly regarding the uproar. I can't speak for the college board as to whether they will do anything about it. The issue is essentially the problem that popped up in il bandito's question a couple of messages back.</p>
<p>For 2 N2 + 3 F2 --> 2 NF3
dH and dS were given in kJ/mol, but it wasn't specified "per mole of what..." </p>
<p>It was apparently meant to imply "per mole of reaction" (ie -264 kJ/2 mol NF3 or /2molN2 or /3molF2). Some people interpreted it to mean -264 kJ/1mol NF3, which changes all your calculations. The problem is this unit format doesn't match what is currently used in some of the common textbooks. (Zumdahl and Brown and LeMay, I'm not sure about others). Zumdahl uses "kJ" to imply "kJ/reaction". It only use "kJ/mol" when it refers to a specific chemical, such as ''kJ/mol NH3". The units used on the test didn't match either of these options.</p>
<p>if you still get 141 at the end, does that mean you did it right, or could it still be wrong?</p>
<p>@gfaith</p>
<p>We were having this exact argument in our class. Our teacher said it is per mole of NF3 but I think it's per each "run" of reaction. So which is it? Do you think they will accept either answer seeing as how they messed up?</p>
<p>@afruff23</p>
<p>Consensus on the AP listserv (the discussion forum for AP Chem teachers) is that the <em>intent</em> was per each "run" of reaction. (-264 kJ/2 moles of NF3, not -264 kJ/1 mol NF3.) The answer key I provided reflects that consensus. </p>
<p>Consensus on the AP listserv is also that the unit convention they chose to express "per run of reaction" is not the unit convention used in many common textbooks. Some on the listserv hope they will accept either interpretation as long as the student is consistent.</p>
<p>Unfortunately, there is actually a reference paper on the college board website that discusses the use of thermochemical units. Some teachers say this paper supports the use of "kJ/mol" to mean "kJ/mol(rxn)" (i.e. per run of reaction). (I've read the paper, and I don't quite interpret it that way. I won't bore you with all the gory details.) Since the paper is posted, I suppose college board could decide to be strict in their interpretation. Most of the teachers who have posted on the listerserv, though, disagree that this is a "generally accepted" convention. I honestly don't have a clue which way the grading will come down. We all await the posting of the scoring rubric. :-)</p>
<p>@whynot123</p>
<p>I suppose there is some random set of accidental calculations that could lead to 141 as the answer, but it's unlikely. If your numbers match the posted answer key, you probably did it right. They do look at the work, though, and a random correct response with no supporting work won't receive points. Also, all the parts have to be consistent with each other.</p>
<p>Can you find the link that supports the one "run" of reaction? We're having senior exams in AP chem tomorrow (juniors like myself must still take it) with all the questions based off the AP Chem 2007 FRQ.</p>
<p>Also, the color question was clear to purple? Excess titrant would cause you to overestimate the amount of Fe right?</p>
<p>lol sorry for being so late...i thought that it would be green to purple, since Fe2+ is green</p>
<p>@ anyone, but especially the guy who posted the grading scale</p>
<p>could u give the weights of each section? thx.</p>
<p>also, does anyone kno when the specific date u can call in and ask for scores is? i think it was june 1</p>
<p>and is it true that there is osme way to pay extra and get a personalized score report that tells u what ur raw score on each section was (i.e. 6/9 on section, 7/9 section 2...)</p>
<p>sry to double post, but what were the weightd of each section (like what you multiplied ur raw score by). id like to try and figure my score</p>