<p>FRQ #2 on partial pressure of oxygen consumed? GG. how'd you guys do it?</p>
<p>Since I knew there was a mole ratio of 3:4 for CO2 and H2O (since it was .600 atm:.800 atm), I wrote CxHy + __O2 → 3CO2 + 4H2O. Knew it had to be C3H8 to balance correctly, making O2’s coefficient 5. Then I did an ICE table:</p>
<p>R:C3H8 + 5O2 → 3CO2 + 4H2O
I: .2 ---- 1.2 ------ 0 ----- 0 -
C: -x - - -5x ---- +3x – +4x
Since it said the reaction went to completion, I knew that x had to be .2 so:
E: 0 ---- .20 ----- .60 ---- .80</p>
<p>So then I knew that .20 atm of O2 were left and thus 1 atm was used. But I don’t think that’s the right way, I kind of made some assumptions…</p>
<p>oh man. i knew that the ratio was 3:4, but i didn’t write it down any where and was trying to figure it out in my head first and i just gave up… i wish i didnt! -.-</p>
<p>Yeah, the thing is, I didn’t really know how to show my work. So I just kinda wrote the equation and went with it lol. Probably not enough for full points.</p>
<p>oh dang it! thanks. i think i woulda figured it out but my brain sometimes locks out</p>
<p>I’m so mad I couldn’t get this… How in the world did you assume C3H8?</p>
<p>Were there many different versions of AP chem test ?
I remember that my AP chem frq #2 had nothing to do with O2</p>
<p>I think I drew a cat skateboarding down a hill for this one…I guess I was close!</p>
<p>I think this is the ONLY way to solve this question.</p>
<p>And I just wrote down 0.2 atm on a whim. 1 point? Pretty please :)</p>
<p>hmmm I dont remember my 2nd frq to be about hydrocarbons…i remember it was somethng about vapor pressure and there was a picture of a piston at the bottom and it said how it was like 1atm or something. Were there multiple versions or something?? I remmeber I had form E</p>
<p>@aguywholovesrice Yes there were two forms. Form E was less common than form O, but i had form e also and know what youre talking about =)</p>
<p>haha alright! I got scared lol</p>
<p>Hm. I got the ratio right, but definitely didn’t do the ICE table.</p>
<p>Damnit. I hate these chain questions. Had to leave the next two (d and e) blank for this one.</p>
<p>@aguywholovesrice, I had a piston thing on the MC</p>
<p>@FutureDoctor12, the thing is that you can continue using a bad number from c onto d and if you do the method correctly you get full points (or so my teacher says).</p>
<p>you, my friend, are winning</p>
<p>Yes, as long as you maintain consistence and actually know the process for the subsequent problems, then you can get the points.</p>
<p>Ex: You don’t know how to answer one part of the question. You throw down a random number and move on. The next part requires you to keep using that number. You know how to solve this part. If you use your random number and continue getting wrong answers, you will score the points for knowing the process - the ONLY point you’ll lose is for the first instance you got the wrong answer.</p>
<p>well, i hope i get a 5. studied everything sunday night</p>
<p>Used PV = nRT most of the time and conversions to get those answers o.o</p>
<p>Darn it: I had 3 moles for HOH and 4 moles for CO2! I did the other stuff right but now I have like 3/4 of the dumb question wrong because of that :/.</p>