<p>^^^That’s really good! I think I’ll just have a look at all of them!!! =D</p>
<p>@happymunkee: GAH SHOULD HAVE FOUND THIS SITE EARLIER LOL great review though!</p>
<p>anyways, how are we supposed to know this? or just memorized:</p>
<p>Which of the following occurs when excess concentrated NH3 is mixed thourougly with 0.1 Cu(NO3)2 aq</p>
<p>Answer is: the color of the solution turns from light blue to dark blue</p>
<p>I stayed home because of studying and because I’m SICK!!! UGH I hate sore throats</p>
<p>I’m actually not going to study for this really. Did my review the other day and I always leave the day before a test open so I just relax and try to get some sleep.</p>
<p>@miheonigirisan: I think it’s because it forms a really weird complex. We never really went over them and they aren’t very common on the exam. Here’s a table that’ll help.</p>
<p><a href=“Coordination complex - Wikipedia”>Coordination complex - Wikipedia;
<p>I would put money on it being a Ksp for FRQ #1.</p>
<p>^ I have been thinking that for like a month considering it has not been on there for a few years</p>
<p>^ My chemistry teacher said the same thing on Friday</p>
<p>Heres a ksp/precipitation problem im having a bit of trouble with </p>
<p>Practice Question anyone?</p>
<p>There is a 500.00 mL solution that is
.0100 M in silver nitrate
.0200 M in lead II nitrate</p>
<p>Ksp AgCl = 1.8 x 10^-10
Ksp PbCl2 = 1.6 x 10^-5</p>
<p>a. What salt can be added in order to precipitate the lead II and/or silver ions?</p>
<p>b. If the salt is added speck by speck, which ion will precipitate first?</p>
<p>c. At the point which the other ion is just about to precipitate, what is the concentration of the first ion remaining in solution?</p>
<p>*ASSUME NO VOLUME CHANGE IN SOLUTION </p>
<p>*hint: adding a soluble chloride lol</p>
<p>but how do you do c? long problem but u guys wanna try it out?</p>
<p>Do you by chance have the answer? I may have a solution, I just want to see if I get it right first.</p>
<p>i only have part of the solution (that AgCl will precipitate first) – missing the rest, so i just thought id post the question on the forums</p>
<p>why dont u post ur solution here and we can see if it makes sense? lol</p>
<p>Hey guys, i really cant seem to get this…this is from the 2009 FRQ 2) part (f):
A student was assigned the task of determining the molar mass of an unknown gas. The student measured the mass of a sealed 843 mL rigid flask that contained dry air. The student then flushed the flask with the unknown gas, resealed it, and measured the mass again. Both the air and the unknown gas were at 23.0°C and 750. torr.
Given that the calculated Molar mass is 40.1 g/mol, and the actual is 44g/mol.
(f) For each of the following two possible occurrences, indicate whether it by itself could have been
responsible for the error in the student’s experimental result. You need not include any calculations with
your answer. For each of the possible occurrences, justify your answer.
Occurrence 1: The flask was incompletely flushed with CO2(g), resulting in some dry air remaining
in the flask.</p>
<p>This is the answer:
This occurrence could have been responsible.
The dry air left in the flask is less dense (or has a lower
molar mass) than CO2 gas at the given T and P. This
would result in a lower mass of gas in the flask and a lower
result for the molar mass of the unknown gas.</p>
<p>Ok, haha.</p>
<p>Well, let’s find the molar solubilities of each one.</p>
<p>AgCl = = 1.34 x 10^-10
x = 1.8 x 10^-8 M AgCl</p>
<p>PbCl2 = [2x]^2 = 1.6 x 10^-5
x = 1.59 x 10^-2 M PbCl2</p>
<p>If you have enough chlorine to allow the PbCl2 to precipitate, you have at least 0.0318 moles of chlorine, which is more than enough chlorine to take all the silver out of solution, so my answer would be 0, though I find it odd.</p>
<p>Anyone else have any ideas?</p>
<p>Ok, so we can use PV=nRT to help us.</p>
<p>Experimental: PV=nRT
(750)(0.843) = (x)(63.2)(296)
x = 0.034 mol CO2</p>
<p>Theoretical: PV=nRT
(750)(0.843) = (x)(63.2)(296)
x = 0.034 mol CO2</p>
<p>So up to this point it’s the same thing.</p>
<p>Now you can use the molar masses you have to see how many grams there should be.</p>
<p>Theoretical: (x g CO2)/(0.034 mol CO2) = (40.1 g CO2)/(1 mol CO2)
x = 1.355 g CO2</p>
<p>Experimental: (x g CO2)/(0.034 mol CO2) = (44 g CO2)/(1 mol CO2)
x = 1.487 g CO2</p>
<p>This means that you had less grams of CO2 in the actual experiment, which means that air, which has a smaller molar mass, weighed less when the mass of the gas inside was calculated, causing the molar mass to be smaller.</p>
<p>@tmanneopen: dont think it should be since u already know the concentration of the Ag which is 0.0100M? </p>
<p>Yea but doubt the answer is 0, damn anyone else got a clue?</p>
<p>I was doing the 2008 exam but was confused about something…
Why would NH4Cl (aq) + HCl (aq) not give visible evidence of a chemical reaction. </p>
<p>And can anybody show the steps involved with doing numbers 67 and 68?
Thanks in advance!</p>
<p>and also this is probably a really stupid question but what’s the difference between covalent bonds and london disperson forces? </p>
<p>For example, in the 2008 exam…
In solid methane, the forces between neighboring CH4 molecules are best characterized as…
the answer is London disperson forces.
(besides the fact that the question has the word “forces” in it, why can’t the answer be covalent bonds?</p>
<p>Real Quick can we make a list of common compounds of the certain shapes?</p>
<p>It will save us some time on the test.</p>
<p>Example: </p>
<p>Trigonal Planar: BH3, AlH3…</p>
<p>covalent bonds are inTRAmolecular forces.
the C-H bonds WITHIN the methane atom are covalent bonds.</p>
<p>London dispersion forces are inTERmolecular forces.
they are due to the occassional ionization of the CH4 atom since the electrons are constantly moving in a nonpolar molecule.</p>
<p>can someone explain what is so important about the reacion between NH3 and HCl? i understand that it makes a white NH4Cl gas when two solutions are close to each other, but why is this important?</p>
<p>also, along that note, what do we need to know about the colors of solutions? e.g. CuSo4 is blue, PbI2 is yellow, etc.</p>
<p>@sporty04 covalent bonds are intramolecular forces, meaning they occur between the atoms of a molecule, while london dispersion forces are intermolecular forces, meaning they occur between molecules
the question asks for which occurs between molecules, ruling out covalent bonds, which occur within</p>
<p>
</p>
<p>(edited out). London dispersion forces occur in non-polar molecules such as O2 N2 Cl2 etc, and in this case CH4 is non-polar. In london dispersion, the electrons accumulate on one end of the molecule, making a slightly negative and a slightly positive charge on opposite ends of the bond.</p>
<p>On a side note, hydrogen bonding occurs between hydrogen and fluorine, or hydrogen and oxygen, or hydrogen and nitrogen. These are the strongest bonds, followed by dipole, followed by london dispersion. :D</p>
<p>correct me if im wrong, this is what we reviewed today</p>
<p>edit: nevermind, i just realized i got covalent and ionic mixed up. sorry</p>