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</p>
<p>Regardless of whether or not it is true for HCN, the fact that CO2 is linear IS what makes it nonpolar. If CO2 were any other shape, the C=O dipoles would not be able to cancel each other out.</p>
<p>The bonds in CO2 ARE identical. There is one central C atom with a double bond to each oxygen atom, ::O=C=O::, so there is the same bond strength and distance between molecules on each side. In addition, the difference in electronegativity is the same for both sides. So the bonds are the same. We could guess that the Os are the negative ends and the C is positive, but each end of the molecule has the same charge and is not polar. Because the molecule is not bent, the C is not an end of the molecule and there is no dipole.</p>
<p>What was the statement about HCN?</p>
<p>For a statement to be CE it must completely explain Statement I. Since Statement II is also true of HCN, HF, or any polar linear molecule, being linear cannot be the complete explanation. We know CO2 has two identical bonds, but that property was not listed as part of the explanation in Statement II. I agree that it is an ambiguous question and seems like it could go either way, but the information listed in II was not enough for I to be absolutely certain.</p>
<p>If this test was the same as May 2008, does anyone know what the curve was?</p>
<p>CO2 question was definitely TTCE CO2 has polar bonds and is non-polar because it is linear…
And I believe this was the balanced equation for one of the problems:
CaCO3 + H2O + CO2 + ----> Ca+2 + 2HCO3-
where they asked you what was the coefficient of H2O
another version of what we saw is located here:
[Hard</a> water - Wikipedia, the free encyclopedia](<a href=“Hard water - Wikipedia”>Hard water - Wikipedia)
CaCO3(s) + H2CO3(aq) ⇋ Ca2+(aq) + 2HCO3-(aq)</p>
<p>what was the answer to the last question ?
heat of fusion
heat of formation
heat of sublimation</p>
<p>^sublimation</p>
<p>It was sublimation.</p>
<p>deposition is gas to solid right? out of curiosity</p>
<p>Yes. It’s the weirdest, most obscure name to remember, but that’s it.</p>
<p>How many CEs?</p>
<p>Actually, it does happen a lot. It happened in biology too.</p>
<p>Yeah, I agree that the test was really easy. I think I got a raw score of 81-83… assuming I didn’t screw up half the bubbling :(</p>
<p>we can miss 10 and still get 780 right? that’s pretty encouraging at least haha… </p>
<p>800s always seem to slip by me. does that happen to anyone else? like you are always capable of 800, but you always end up with like 790 or something ridiculous like 690 instead?</p>
<p>miss 10 and get 780?!?!?!?!?!?!?!?!?</p>
<p>missing 10 is 13 off of raw score!!</p>
<p>72/85 = 780?</p>
<p>that would be miraculous</p>
<p>I wasn’t sure about which species could NOT be appropriately collected over water:</p>
<p>I. Oxygen
II. Hydrogen
III. HCl</p>
<p>Had no idea, guessed HCl. Does anyone know the concept?</p>
<p>BTW, had an A in AP Chem, averaged 760 on CB and SparkNotes practice tests. Skipped 2, confirmed 1 wrong. Lol @ me ^^. Longshot 800.</p>
<p>I think it has something to do with the fact that HCl would dissociate in water because it’s a strong acid. Also… never in my life have I seen a problem where HCl is collected over water.</p>
<p>First of all, HCl at room temperature is a liquid. Secondly, as soon as the “gas” hit the water, it would dissociate. </p>
<p>Not only that, I just looked it up, and the BP of HCl is 110C. This means that in order to collect any HCl gas you would need temps of 110C+, and at those temperatures water would be boiling like crazy. So realistically, there’s no way to collect HCl gas through water displacement.</p>
<p>The reason that you can’t displace HCL with water is because HCL is polar covalent, and so is water. So HCl will dissolve in water (remember like dissolves like). The same situation occurs with NH3+ ammonia which is why ammonia also can;t be displaced by water. On the other hand O2 and H2 are nonpolar covalent and would not be soluble in water, therefore they can be displaced over water.</p>
<p>Dissolving gases in water is a bit different though… CO2 dissolves in water at high pressures.</p>