June 2008 - Chemistry

<p>i got 4400, since you have to account for the energy needed to turn the substance into vapor which is 200J/g and you have 10g on top of the 2400J needed just to reach that temperature which is 80 degrees</p>

<p>i put 2400. do you remember the wording for that question? does it say 'turn into vapor'?</p>

<p>Yeah, I'm quite sure that it said the energy required to turn the liquid into a vapor. It also gives the conversion rate (200J/g) for the substance to become a gas, which is why I picked up on that</p>

<p>can a raw score of -5 be a 800 (with previous experience from tests)?</p>

<p>for the (m)(cp)(∆T) question, does anyone know if 4400J was letter C? I don't know why i remember letters and not numbers.</p>

<p>But for that question, the boiling point was the same as the final temperature, and did it specifically say that it turned to a vapor?</p>

<p>I took an old chem test, one of those only given to certain education agencies or whatever, and I got -8 (raw score 75) and a 780. This test was significantly harder than that test. I seriously doubt that the 800 cutoff is three wrong or something along those lines. There's far too much ambiguity for that.</p>

<p>I'm pretty sure 4400 J was answer E. I'm almost positive that is the right answer.</p>

<p>i got this too</p>

<p>for the KCl it is saturated, because that means if you add any more there will be a precipitate (Which I think was choice I, and the answer was choice I only.)</p>

<p>Guys for that temperature problem i think the answer is 2400. The boiling point of the liquid was 80 and they wanted to the energy to change it from 20 to 80. BOTH liquid and vapor can exist at 80 degrees. </p>

<p>c=4
m=10
delta T=60
heat of vap.=80 </p>

<p>If u use q=mct u get 2400. If u add the heat of vap to it u will get q=m*(heat of vap) which eaquals 800.</p>

<p>2400+800=3200(wasnt an asnwer choice)</p>

<p>The answer has to be 2400, because no matter how u use the formulas, there is no way of getting 4400.</p>

<p>i got 4,400...</p>

<p>the heat of vap is 200J/g</p>

<p>CRAP. I thought the heat of vap. was 80. How did i mix that up?</p>

<p>80 was final temp/boiling point
basically, you got 2400J to change the temp and 2000J to vaporize it</p>

<p>CRAP. I thought the heat of vap. was 80. How did i mix that up?</p>

<p>Two steps</p>

<p>A. Find the amount of energy needed to raise the temp to 80C</p>

<p>B. Find the amount of energy neede to vaproize the substance. You need to multipily the mass by heat of vaporization</p>

<p>The answer is 4400</p>

<p>Btw does anyone know the curve for the May test?</p>

<p>what was the answer to the question about making a solution or something. </p>

<p>i remember i was stuck between volumetric flask and a buret?</p>

<p>and. what as the answer to the questino about the object to see precipitation or whatever.</p>

<p>was it the test tube.. or the really weird looking thing</p>

<p>It was the volumetric flask and the test tube.</p>

<p>Does any1 remember if they got 3 FT in a row around the 110-114 area??</p>

<p>I am so angry right now. This has been haunting me as I went to bed last night. On one of the TF questions, it asked a simple question about which atomic weight was higher. Well, I actually read the question(from part I and part II), and I decided that the intermolecular forces(or whatever it was) had nothing to do with atomic weight but with hydrogen bonding so I put false on the second part. And I'm pretty sure that was wrong. :( Come on, which has a greater atomic weight? How did I miss that?</p>

<p>Oh yeah, one more question. For the speed of the molecules, I thought the speed was only dependent on the temperature and molar mass (root mean square). Would the volume not matter? If the volume went down, the pressure would go up since the molecules would be traveling at the same speed.</p>