<p>woah highest FR last year was 95? That’s pretty surprising 
they must grade the explanations more strictly than the published answers or what? or maybe not. Hopefully I’m not overestimating my score by a lot ugh.</p>
<p>@Sophia, so the coordinator gets all that info?</p>
<p>Urg the stress of waiting is killing me!
For the people who have already taken the National Exam, did you think the FRQ’s were harder (by a lot) than previous years? I felt like the difficulty level went up a lot, so do you think that below an 88 would still be good to go to camp? I feel like I got 56 or 57 on MC, 80 on the FR and average on the lab? Sorry to ask so many questions but I’m really worried.</p>
<p>Thanks in advance ~</p>
<p>Yeah, I’m really nervous too. I don’t think the FRQ’s were that much harder than previous years though. Less analysis and more regurgitating facts.</p>
<p>Does anyone know if the MC matters after top 150, or is only the FR used after that to determine the top 20? Or is it that they give everyone a score for the MC and a score for the FR and add them up to see what the top 20 highest MC & FR scores are?</p>
<p>After top 150 is decided, they consider MC+FR+labs for top 20. MC is 3/8 of the total; FR is 4/8 of total; labs are 1/8 of total.</p>
<p>So something like this formula: 1.25*MC (max 75) + FR (max 100) + labs (scaled to 25) = 200 max total score.</p>
<p>I wanna say that top 20 cutoff is 165-170 (maybe a little less for this year).</p>
<p>What is the cut off for the top 50? And is the top 150 based only on MC?</p>
<p>I don’t know any cutoffs - I was just estimating so that I would get in comfortably :P.</p>
<p>From information gathered over the years, I guess this is what they do: After receiving all the tests, they put all the Part I scantrons in the machine and the computer tells them the top 150 scores. These names appear on the Honors list. They retrieve the Part II and Part III booklets of these students and throw the rest in the trash (metaphorically). They grade these 150 blue books and labs according to a rubric. They weight the three Parts accordingly (3/8; 4/8; 1/8) to find the total score - the formula has to be essentially the one I posted above. Top 20 and 50 are decided based on total score.</p>
<p>just to say Hello to everyone who took the national chemistry olympiad test.</p>
<p>So a 57 on MC, 80 ish on FR and average on the lab will not be enough to get to camp?</p>
<p>I heard that the free response is graded pretty harshly especially on your explanations because no one can ever score a perfect on those, but there has been many instances of perfect multiple choice tests. Hopefully I get an easy grader haha.</p>
<p>Labs are graded hard too, if you don’t do more than one trial you can’t achieve the “excellent” score, you must support your data with both quantitative and qualitative data, etc.</p>
<p>I think this year’s multiple choice is about the same difficulty as last year’s, maybe a bit harder. Free response was definitely harder (#8 grr).</p>
<p>again, last year’s top 20 averages were 55 MC and 88.4 free response so with 57/80/average, you have a chance but I guess the only thing you can do right now is hope everyone else fails FR haha.</p>
<p>Just wondering, was anyone here really confident about #7 or #8 on the free response? also, I think the testing window ends tomorrow lol, I’m itching to discuss some questions.</p>
<p>This is the powerpoint my teacher forwarded to me from the chem O coordinator: <a href=“http://www.4shared.com/office/yeRoZHEi/ChemO.html?[/url]”>http://www.4shared.com/office/yeRoZHEi/ChemO.html?</a></p>
<p>you can find info on the national exam like averages, performance, etc. (skip to slide 13 for averages and cut-off to get top 150).</p>
<p>The testing window ended today, I doubt anybody will still be taking the test later than this moment, so I think it’s reasonable to assume we can begin discussing the exam.</p>
<p>Around when will we get our multiple choice scores back?</p>
<p>@Sophia, I believe averages/cutoffs in the powerpoint are only for the 2010 exam (the “hardest questions” on it were all from that year).</p>
<p>And there were some difficult never-before-seen explanation questions from that year (particularly 4b and 4d), even though most of the test was easier. Well, I generally find kinetics annoying, but I guess high score of 95 is not as surprising anymore. I do not think there’s a reason to believe they grade it any more strictly that the published answers (and if you read some of the published answers on #7, you’ll see it’s not THAT strict).</p>
<p>Yeah, number 4 was a bit weird, though the equations necessary to solve it were given to you. 4d seems out of place (maybe #7 would have been a better place for it).</p>
<p>The published answers on #7 usually aren’t very strict, and I agree that they won’t be much stricter while grading. So, I hope they’ll give me partial/full credit for my answers that could have been a bit better (I was running out of time). I’m not sure what will happen.</p>
<p>I thought that 33 and 45 on the MC were a bit tricky. I got 45 wrong, but 33 right.</p>
<p>I don’t want to provide many specifics because it is not yet April 24. I want to be safe.</p>
<p>I was talking about #4 on 2010, but I agree.
Seems like everyone missed 45 though.</p>
<p>Guys the window is over TODAY, not tomorrow. We can safely discuss the tets.
@barley81, what were #33 and #45? I know I got the one about pH for two acids wrong, and then I missed the one about batteries, and I may have missed the Mg5O4 one (but I don’t remember what I put).</p>
<p>random notes from the test
Part I
atmospheric nitrogen reacts with Mg
-56 degrees ice
(#33) converter oxidizes CO, reduces NOx
CdCO3 precipitates, AgCrO4 does not
2.33 Cu oxidation state in YCBO
nicad and lead are rechargeable, dry cell is not
3d has zero radial nodes
(#45) 1s is best at shielding
linolenic acid has 3 C=C bonds
Part II
2 dichromate : 3 ethanol
~24% ethanol in mouthwash
0.31 M ammonia to dissolve
blue precipitate forms, which redissolves to make solution that is dark blue
e- and cations move toward Pt electrode
Ecell decreases after adding barium
Ecell does not change when electrode size is doubled
acid ionization decreases entropy, because ion-dipole forces order the water molecules
Al(OH)3 + HF -> Al3+ + H2O + F-
I- + H2O2 -> I2 + H2O + (OH- whatever)
Hg2 2+ + Cl- -> Hg2Cl2
NaS + H2O -> Na+ + HS- + OH-
NO2 + H2O -> H+ + NO3- + NO
chain polymer thing + HCl
inner shell d electrons are poorer shielders than p electrons, so IE trend is most exaggerated for smaller atoms that don’t have d electrons
polar protic solvent, to interact with OH- group so that cation forms independently; also to solvate cation and further stabilize it
I put “beta-branching on 2-methylbromobutane makes substitution rate most similar to secondary alkyl bromide, due to steric factors hindering attack of OH-”. They would also accept primary alkyl bromide just because their both primary.
SN2 (Mechanism II) inversion; SN1 (Mechanism I) racemic</p>
<p>Are you sure your ethanol % is correct? I remember getting something like 12%, did you multiply the correct answer by 2 somehow or did I divide it by 2 somehow?</p>
<p>shouldn’t it be polar aprotic? since the H+ would ‘steal’ the OH- and thus make it a weaker nucleophile in the sn2 reaction</p>
<p>@thenerdyjew, can’t really answer that can I? But Internet says listerine is 26% ethanol, I might be wrong though.</p>
<p>@ lenov, did they ask for sn1 or sn2? I thought they asked what kind of solvent increases the rate of unimolecular reaction?</p>