<p>If any of you guys need any help with nuclear chemistry, we did some quick review of that a couple weeks ago, just in case we needed it. I can explain some of it and answer some questions.</p>
<p>Can someone please explain this question to me from the 5 steps to a 5 practice exam, I’m very confused and the explanation did not help much.</p>
<p>If a solution of ethyl ether, (C2H5)2O, in ethanol, C2H5OH, is treated as an ideal solution, what is the mole fraction of ethyl ether in the vapor over an equimolar solution of these two liquids? The vapor pressure of ethyl ether is 480 mm Hg at 20°C, and the vapor pressure of ethanol is 50 mm Hg at this temperature.</p>
<pre><code>0.50
0.76
0.91
0.27
0.09
</code></pre>
<h1>9 You use D=MP/RT</h1>
<p>I think ethane. </p>
<h1>10 I think butane because it is the longest carbon chain.</h1>
<p>@ Dedicated, I think the answer is probably C (0.91), since by Raoult’s law, the partial pressure is equal to the pressure multiplied by the mole fraction. And 0.91 = 480/530.</p>
<p>Does anybody know if we need to use a non-graphing calculator? Or can we use our graphing calculators?</p>
<p>you can use a graphing calculator</p>
<p>You can use whatever calculator you want as long as it isn’t on the prohibited list.</p>
<p>This is crazy. I am so not ready for tomorrow…
Currently reviewing (STILL) and have solved only ONE practice test. And that was two weeks ago -_-
Btw, it’s 3:00 AM here in Pakistan right now…</p>
<p><a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>Supporting Students from Day One to Exam Day – AP Central | College Board;
<p>in 1, C, (ii), the answer uses 3 sig figs but Ka only has 2 sig figs?
In the past, i’ve seen CB use only 2 sig figs when only 2 sig figs were mentioned in Ka/b.</p>
<p>Anyone know what the range for a 5 is? I heard a few years ago it was a 60% and above. Is it still the same?</p>
<p>It changes every year, but I think it’s around there, maybe a bit higher, like around 65% or so.</p>
<p>@Jwen556:
This is what my teacher told me:
It’s because when using log, the number before the decimal point does not count towards the sigfigs (it can be determined without the log). Only the digits after the decimal points count towards sigfigs.</p>
<p>i.e. log(102) (3 sigfigs)
The number before the decimal point is definitely 2.
Therefore, the answer is 2.009</p>
<p>Would you happen to know how the MC and FR were weighted? Is it 50-50?</p>
<p>Both are weighted as 50% of the overall score.</p>
<p>I’ve heard 100/150 points is a 5</p>
<p>I took the pratice test and missed 42 MC. I suck.</p>
<p>Done! Prep is complete and 3 hours to test!!! :O</p>
<p>I keep getting low 50s on the MC, and my FRQ scores are so random… this is annoying. I just want to know if I’m getting a 4 or a 5 lol.</p>
<p>@Jwen For concentrations the number of sig figs determines the number of numbers after your pH. Your pH will be three sig figs therefore your concentration is two. That’s the best reasoning I can get out of it.</p>
<p>I’d say a 65% or around there is a five.</p>
<p>@Descuff You took another one and that’s what you got?</p>
<p>@Descuff You need to pace yourself harder. On your watch, try to do everything in half the time.
I took the SATII Chemistry a day ago. I know it’s cake as compared to AP Chemistry but the real challenge is finishing the test. Which I accidentally got myself to do because I thought there were 85 questions other than the 10 Section B questions and ended up trying to really speed up. GOOD LUCK. </p>
<p>It’s 3:50 am here in Pakistan. So 3 hours left before I leave for the test!</p>