AP Chemistry Review Thread

<p>Is the answer to #25 on the 1999 MC, C? I don't have the answer key with me. I am sure the two phases coexist between R and S, and do not between S and T, but I'm not sure between Q and S. But just the first two statements justify my thinking that C is right.</p>

<p>The answer is C. I have the answer key.</p>

<p>The dip is supercooling, which is when a liquid is chilled below its freezing point but does not become a solid. So as crystals begin to form again, the temperature will rise slightly and then remain constant as it freezes.</p>

<p>I remember that my teacher saying something along the lines of super-cooling. Something to do with salt. I am not sure.</p>

<p>Put in order of strongest to weakest the following bonds/forces:
-H bond
-dipole-dipole
-dipole-ionic
-metallic
-network covalent
-covalent
-ionic
-london dispersion</p>

<p>My q got buried...</p>

<p>Is knowing PR, reading + rereading it enough to get a 4/5? I've been taking practice tests from other books and not doing so well...</p>

<p>Austin - you answer is ok until the last step. Once you've multiplied by Faraday's constant, your answer is in mol e, next</p>

<p>x 1mol Al/3 mol e- x 27g Al/1 mol Al </p>

<p>This moves the 3 to the denominator and adds a 27 to the numerator (Answer C)</p>

<p>thank you, gfaith. I get it now.</p>

<p>yes, PR can definitely get you a 4. I am not sure about 5.</p>

<p>afruff, I can arrange some, but not others.
Because diamond (coordinate covalent) is stronger than an ionic bond.
but I think sand is also a coordinate covalent.
So I am not sure.</p>

<p>But in general, we can arrange some.</p>

<p>I didn't know if you were asking a general question to the audience, or if you didn't know, but it has been done:</p>

<p>Put in order of strongest to weakest the following bonds/forces:
(note: not sure about dipole-ionic and metallic, so excluded them)</p>

<p>-network covalent
-ionic
-H bond
-dipole-dipole
-london dispersion
-covalent</p>

<p>Diamond is not coordinate covalent. You meant to say netowrk covalent.</p>

<p>opps, always mix those up</p>

<p>wouldn't covalent be stronger than london dispersion?</p>

<p>I think covalent is stronger than london dispersion most of the time. If the atom is large enough, london dispersion can be stronger than covalent. But that's just what I think. Not sure if it's right or not.</p>

<p>I think there must be some confusion about "covalent". Covalent refers to bonds <em>within</em> molecules. It's the strongest type of bond - after all, network covalent compounds are just giant networks of covalent bonds. (Diamond is essentially one giant molecule.) LD, dipole-dipole, and H-bonds are forces <em>between</em> molecules. They are all much, much weaker than covalent bonds.</p>

<p>gfaith got it right. Just think how hard it is to break apart NH3 into its elements or CO2. However, I said which force/bond is the strongest. I didn't specify intermolecular or intramolecular.</p>

<p>dunno if anyone's on, but</p>

<p>It's the last day before testing, and as luck would have it I am insanely behind on reviewing. Should I change gears into super cram today or will I be too burned out for the test? What are you guys going to do?</p>

<p>super cram....</p>

<p>This is not going to turn out well, heh.</p>