<p>arrr,…1 blank, 4 wrongs so far
is 79 good enough for a 800??</p>
<p>79 is right on the border, or so I’ve heard. Whatever, I’m not a perfectionist; a 780+ and I’m happy.</p>
<p>so would -2 be rounded up to -3?</p>
<p>I think its T T to the question about CO2 being nonpolar despite having polar bonds. It could go both ways, but it says
“BECAUSE co2 is linear” – linear doesnt mean nonpolar… take HCN for example. what does anyone else think?</p>
<p>tahts why i hate T F CE -.-</p>
<p>HCN isn’t soluble in water so wouldn’t that make it nonpolar?</p>
<p>Any linear molecule I think of has both dipoles pointed inward (thus being canceled) or both dipoles outward (thus being canceled). Not sure.</p>
<p>1) and for nacl weighing more… that one is T T CE because of the freezing point depression equation, which involves molality. Thus, NaCl weighing more DOES affect the freezing point</p>
<p>2) what was the question with purple crystal?
think it was part of matching… i thot I read “vapor CONDENSES on crystal” so i put condesation… apparently it read “crystal turns into vapor”?</p>
<p>right but being linear by itself doesnt mean it’s nonpolar. I think for it to be CE it had to say “dipoles cancelled” or something, like I’ve seen on some tests.</p>
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<p>No, molality is mol solute/kg solvent. You could have 58 g NaCl in 1 kg solution and 74 g KCl in a separate 1 kg solution, but they’ll have the same freezing point depression. Both solutions are 1 m and both dissociate into 2 mol of ions. KCl weighs more, but that doesn’t affect the freezing point. </p>
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<p>A purple vapor appears above crystals of iodine –> sublimation. Definitely was not condensation (do you really think they would put “condense” in the question if the answer was “condensation?”)</p>
<p>ah crap. there goes 800.</p>
<p>It’s OK man. As long as you’ve got 750+, you’re good.</p>
<p>linear means the effects of the 2 polar bonds cancel each other, making the whole molecule nonpolar :)</p>
<p>CO2 is a linear molecule. So although both bonds are polar, the O’s are pulling on the C with equal force so the polar bonds cancel out and there is no dipole to the molecule.</p>
<p>Iodine is a dark purple-black solid that forms a purple vapor at room temperature. I2(s) –> I2(g) = sublimation.</p>
<p>For the displacement in water, gases will displace water in an upside-down graduated cylinder filled with water and placed in a water bath (I did this experiment before in Chemistry with Zinc and HCl), with a hose connecting the water-filled graduated cylinder to a flask where a reaction is taking place. The gas travels through the hose, into the cylinder, and forces the water into the bath. H2 and O2 are gases and can be products of a reaction and displace water, but HCl dissolves in the water and can’t displace it.</p>
<p>That test was insanely easy. After taking some sparknotes/REA practice tests, I thought I was f***ed, but I don’t think there was a single question that I got wrong on the actual test (unless it was some careless error). Uh oh, now I’ve probably jinxed myself…but it really wasn’t too bad I thought.</p>
<p>So I’ve been reading about the discussion of the answer for the XY combination-- Al has a charge of +3, and metals in the column you were combining with it have a charge of -2. I don’t understand why it wouldn’t be X2Y3- could somebody please explain?</p>
<p>The “column” was the halogens, so it would be AlCl3, for instance.
However, there was a question with Al and something else in a 2:3 ratio.</p>
<p>Oh okay- thank you!</p>
<p>On collecting gas over water, I believe that collecting oxygen isn’t legitimate because a small percentage of oxygen does dissolve in water, resulting in a yield that wouldn’t be accurate for whatever experiment you’re doing.</p>
<p>Nope, you definitely can because I remember my teacher collecting oxygen gas in a lab through the decomposition of KClO3.</p>
<p>The hydrolysis of water allows for a test tube to be filled with oxygen gas.
Therefore, O2 can be collected.</p>
<p>CO2 is linear, but that only explains its being nonpolar if you assume the two bonds are identical. Statement II said CO2 has 2 polar bonds and is linear, but it didn’t mention the bonds were the same. Statement II is also true about HCN, which is a polar molecule, so the answer was TT not CE.</p>