<p>Nah I’m a sophomore, but I’ve put so much work into this and studied so much that it’d be really frustrating not to make it</p>
<p>Yeah same here, my teacher was worried that I wouldn’t make it because I spent 2-5 hours every week after school with him to get all my questions answered. It would suck not to make it, because that would mean I wasted so much of his time. But even if I don’t place top 20, studying for this wasn’t a waste of MY time because I learned so much and now Chem AP is a joke :). it has also increased my love for chemistry. Lol I sound like a corny dork.</p>
<p>Yeah I stayed after school like 2 hours a day every day for 3 weeks, bugging my teacher for help with a bunch of questions, it would really suck not to get to camp.</p>
<p>Who knows, maybe I did better than I thought.
Or maybe I just failed it…</p>
<p>So, on the ice one, I got -13.6 degrees as well. Why was that wrong?</p>
<p>I don’t remember the #s but I checked it multiple times and got -33</p>
<p>Huh, I checked mine as well, and I kept on getting -13.</p>
<p>I keep getting nearer to -13 degrees now (using approximate numbers I remember).
I messed this up during the test because I had the fusion of ice on the wrong side of the equation. Only cooling the water releases energy.</p>
<p>If the rate I find out wrong answers continues at 1/day, I’ll have a 46 MC by May 4th xD.</p>
<p>I remember I did:
-Qwater = QIce
so
- (m)(C)(deltaT) = (grams ice)(heat of fusion of Ice) + (grams ice)(Cp of ice)(Final T - Initial T)
I got -33</p>
<p>Yeah, I had this issue on the exam. Usually, I do the heat loss = heat gained type problems straight into the calculator without writing down the expression, but I made sure to write it down on the paper with the values and the unknown. I repeatedly got -13, so I’m fairly sure that is the correct answer.</p>
<p>@thenerdyjew: You forgot to account for the mass of water from the melted ice being heated up.</p>
<p>@ thenerdyjew, Cp for water and ice are different on the right side of the equation. After 0 degrees, it changes from 2.06 to 4.18. Sorry if i just lowered your score ;(.</p>
<p>wait, so that extra 4.3g could really have created a difference of 20 degrees?</p>
<p>yep, cuz Cp for water is significantly higher than Cp ice</p>
<p>Answers for 11, 28, 32, 38, and 45?</p>
<p>gah sitting at around a 46-50 hoping still good enough for top 150</p>
<p>45 was C i think. Einstein’s explanation of the photoelectric effect proved the wave/particle duality of light (quanta etc.). I got that wrong.</p>
<p>I got A for 11. Magnesium nitride has a lower mass percent of magnesium than magnesium oxide. The weight gain should be lower than expected.</p>
<p>For 28 I got B. Reaction 1’s rate constant is more dependent on temperature so it has a higher activation energy. At lower temperatures reaction 2 will be faster than reaction 1.</p>
<p>For 32, the pH’s of the equivalence points cannot be equal since conjugate bases of weak acids are basic. If the initial pH values are the same, you have far less strong acid than weak acid. The volumes of NaOH needed are vastly different. D (neither).</p>
<p>For 38 I got B, -0.56V. The given reaction is one that is made up of two half-reactions with negative E.</p>
<p>@thenerdyjew @youtwothirtyfive
For the water one, I checked and I also keep getting ~-13 degrees. Ice has an abnormally high heat of fusion.</p>
<p>@barley, do you have a copy of the MC? Or do you have a really great memory? :P</p>
<p>For 11, that may be true, but wouldn’t heating the Mg long enough then cause the magnesium nitride to decompose back into MgO? I read somewhere that it did.</p>
<p>@Harvey, I don’t any of the other choices were as reasonable though. (B) actually causes Mg:O ratio to be lower. (C) (length of magnesium?) and (D) did not affect results.</p>
<p>I should probably stop obsessing over this forum and pay attention in APCS… >.<</p>
<p>@barley81–also for #33 (which I know I got wrong), isn’t the pKb of hydroxylamine lower than that of methylamine? (.3 < 3.38 I think according to wikipedia)</p>
<p>@dobbyoshi Darn… 57. I suppose it’s the 2 lone pairs on the oxygen that enhances the lone pair on the nitrogen.</p>
<p>@YouTwoThirtyFive I have a copy. The exam can be handed back to students after April 23.</p>