<p>I agree with you on the MC scores, but I’m expecting the FR to be as low as 80 ish, due to the intense difficulty of this year’s test (it would be safe to assume that 95% of the kids who took the test probably got most of #8 wrong). This was my first year taking the test, so I don’t know how to compare the lab to last year’s, but I thought it was pretty strait forward.</p>
<p>I’m feeling that 55/90/average is the highest the cutoff can be this year. Most of the camper MC scores will be cluttered around 55-57, because of all the evil tricks. So the cutoff really depends on FR. If like >15 people bossed #8, then FR cutoff will be 85-90. If <10 people bossed it, then I’m thinking more like 80-85. </p>
<p>Also, how many possible marks do they give for labs: is it below, avg, excellent? or below, avg, above, excellent?</p>
<p>philoscott, i made the same mistake as you on the orgo section. how much partial credit do you think they’re going to give us, out of 14%?</p>
<p>@YouTwoThirtyFive, I think that sounds correct.
So far my MC is at like a 56 and my FR is at like an 81, hopefully good enough?</p>
<p>my guess is this is how they’ll score it:
a) 1 point for tertiary, 2 points for correct explanation
b) 1 point for tertiary, 1 points for correct explanation
c) 1 point for polar protic, 1 point for correct explanation
d) 1 point for correct isomer, 1 point for primary/secondary + (1 point for correct explanation consistent with previous choice)
e) 2 points for correct assignments, 1 point each for correct explanation consistent with assignments.
best case scenario: you would lose only 4 points (assuming b, c, and e are the only answers affected by mixing up SN1/2). If they are mean, you would lose 8 points.</p>
<p>wow, thanks U235! 
i didn’t remember what the subsections were exactly and thought i was going to lose all 14 points when i first realized my mistake lol</p>
<p>yay! i forgot the question but im happy to see i got nearly 100 on it :)</p>
<p>jw tho, what did a) ask again?</p>
<p>Which of the isomers reacts fastest by substitution with OH-?</p>
<p>If the solvent is water, then it’s tertiary because SN1 is faster than SN2 in protic solvents (since they didn’t tell you the solvent, I guess this is what you assume).</p>
<p>However, sidenote: if the solvent was aprotic, like acetone, the correct answer would be primary.</p>
<p>Then I guess if you wanted to get technical, tertiary alkyl bromide actually undergoes mainly elimination in standard conditions, since OH- is strong base and the tertiary cation intermediate is a strong acid.</p>
<p>I was discussing the test with the proctor (who has a PhD in Chem) and she verified that it is tertiary, tertiary, polar protic solvent</p>
<p>How many points do you think I’d lose for not saying polar PROTIC solvent, i.e. just saying polar solvent?</p>
<p>Depends on the explanation. In it did you imply the properties of a protic solvent?</p>
<p>hm… i assumed that since OH- is a strong nucleophile, it would be a sn2 reaction. i also assumed sn2 because whenever i see sn2 reaction examples they’re most commonly with OH- and sn1 is most commonly with H2O. so i put primary, but i could be wrong</p>
<p>@U235, I pretty much guessed as I had no idea, so my answer was partially correct but pretty sure the explanation is wrong. So maybe I’ll get like 1 out of 2 points?</p>
<p>@lenov, That’s why I still don’t like this problem. It seems they were aiming for tertiary (see 2004 Part I), but under certain conditions the answer could definitely be primary. My chem teacher’s (who has a phD in orgo) first response when I asked him was primary because he said it’s hard to isolate tertiary cation in basic solution; I didn’t bother him further with usnco’s intended answer (which depends on stability of tertiary carbocation). That’s why I really hope they give credit for explanations consistent with multiple choices.</p>
<p>@thenerdyjew, sorry, I don’t know.</p>
<p>im looking at the 2005 part I (here’s the link so you don’t have to spend time finding it: <a href=“American Chemical Society”>American Chemical Society) and i can’t find which question you’re referring to >< i thought stability of carbocation was only important in sn1 reactions tho, lol i don’t like this question either</p>
<p>sorry, it’s 2004 Part I.</p>
<p>part (a) only asked which isomer substitutes faster, making no distinction between SN1/2. Indeed, SN1 for tertiary is faster than SN2 for primary in polar protic solvents when/if substitution actually occurs.</p>
<p>However, I’m still tempted to say that the tertiary undergoes E2 elimination much more readily than substitution in these conditions. </p>
<p>Even more confusion: 2004 MC question only asks which reacts fastest (not which substitutes fastest ). Then it’s definitely the tertiary. I think this year’s FR asked which substitutes fastest… the answer can still be tertiary, but I believe primary should also be accepted if explained correctly.</p>
<p>what was the hardest question this year? any consensus on that?</p>
<p>Please let me know when we obtain the results of the Nationals exam</p>
<p>@ChemistryTutor–I think the consensus is that the hardest Free Response question was number 8 (about nucleophilic substitution), given that most students don’t take organic chemistry. That said, some of the reactions (1, 2, and 6 I think) were difficult and new to the test (see posts #139 and #242). </p>
<p>For the Multiple Choice, some harder questions were “what does Einstein’s explanation of the photoelectric help to explain” (answer: wave/particle duality of light) and “which electrons are the most effective shielders” (answer: 1s). Other I thought were pretty challenging were “which is the most basic” (answer: methylamine < ammonia < hydrazine < hydroxylamine) and “what’s a Grignard reagent” (answer: R-MgBr).</p>
<p>Correction: methylamine > ammonia > hydrazine > hydroxylamine in basicity. See post #225 for the specific pKbs.</p>