<p>Alright, well I guess it could be question 6.
Do you guys think an entire question on solutions is likely?</p>
<p>I got:
Cr2O7^2- + 3H2S + 8H+ —> 2Cr3+ + 7H2O</p>
<p>You do the half reactions.
Cr2O7^2- —> Cr^3+ and H2S —> S</p>
<p>Could anyone help me with these questions?
<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;
<h1>'s 24, 33 and 70 ?</h1>
<p>Niquii77 how did you balance those half reactions?
I keep getting:
2 ( 9e + 14H^+ + Cr2O7^2- —> Cr^3+ + 7 H2O)
9 ( 2e + H2S –> S + 2H^+)
What am I doing wrong?</p>
<p>24- you need to flush with a dilute basic salt.
33- think of how many moles of Cl- are in the solution. (.1 mol from NaCl and .2 mol from CaCl2)
46-I’m not completely sure about this one, but I think it might form a complex ion?
70- Na+ has the most number of moles, so that is the greatest, and then with PO4 and NO3, think of what reacts with silver which has a negligibly small amount remaining.</p>
<p>(Anybody can feel free to correct me.)</p>
<p>@met Your first mistake was that you didn’t balance the non Ocygen and Hydrogen elements. Your Cr3+ would be 2Cr3+. I believe that is what ran your reaction amuck.</p>
<p>Can anyone give a quick run through on bonding? Plus how do you know if something is non polar or polar? And how do you know if something has London dispersion forces, dipole dipole, etc? Thanks.</p>
<p>Thank you!
Also, how do you know when a question is asking for LR/excess type problem?</p>
<p>@future
nonpolar - dipoles cancel ( linear, symmetric, diatomic) , london dispersion
polar - dipoles don’t cancel(anything with unpaired electrons except for linear(?) are polar), dipole-dipole
hydrogen bonding H-F, H-N, and H-O
and everything has london dispersion</p>
<p>Polar molecules are asymmetrical. Nonpolar molecules are symmetrical. Nonpolar bonds have equal dipole moments (F–F has a nonpolar bond and a nonpolar molecule. O=C=O has polar bonds but is a nonpolar molecule)</p>
<p>Wow niquii. I’m betting my entire life savings to say that you will get a 5</p>
<p>It’s basically a LR problem if it gives you the number of moles that react with another substance, I think.</p>
<p>London dispersion is a nonpolar to a nonpolar intermolecular force. They are the weakest. Dipole-dipole are between multiple polar to polar bonds. Hydrogen bonds include Hydrogen being attracted to N, O, or F very strongly. Ion-Ion bonds are ionic crystals. Ion-dipole is an ionic substance attracted to a covalent substance (NaCl attracted in water. Hydrated ions)</p>
<p>Could someone explain the difference between ideal gases and nonideal gases? And what temp and pressure have to do with it?
Btw, if anyone needs to take one last practice test or something, I have 84, 89, 94, 99, 02, 08, and the audit exam</p>
<p>Ideal gases have NO intermolecular forces, negligible space between particles, kinetic energy is conserved in their collisions, and have random and unpredictable motion. Completely ideal gases are not actually existent, but gases are most like ideal gases when they are in high temperature and low pressure conditions. :)</p>
<p>How do you know when dipoles cancel? Like how can you tell from NH3 or CO2 for example.
Thanks to everyone who explained!</p>
<p>High temp = particles are farther apart and low pressure = ?
Why do high pressure and low temp make gases non-ideal?</p>
<p>@future
You could draw the structures
Nh3 would be triangular pyramid because of its unpaired electron, since it’s bent, the dipoles don’t cancel, so its polar
CO2 is linear i believe, so its nonpolar</p>
<p>High temperature makes the molecules move faster, which is want you want for IDEAL. Low temperature wouldn’t allow this.</p>
<p>High temp, the average kinetic energy is higher so they move around faster and are more energized. While low temp does the opposite, they move around slower etc.
Low pressure, they aren’t as compressed and there is more space between the particles (and there aren’t as many particles in one space) so they can move around more. And high pressure, there is limited space between particles and they can’t move around as freely.</p>
<p>Thanks. So the ideal gas law assumes that the attractive forces between the particles is negligible? When the particles are closer together, the attractive forces are stronger, so the ideal gas law doesn’t apply?</p>
<p>Aww, thanks, Descuff! <3 I better if I want to beat you in our bet. ;)</p>
<p>I say you can get a 4 if you take what’s in your brain and put it on your paper.</p>
<p>@mets It’s not that the ideal gas law doesn’t apply. It just that what the ideal gas law says will happens isn’t what actually happens to a real gas under those circumstances.</p>
<p>Does anyone have any strategies for question 4 on the free response? Also, what are the chances of Acid/Base Titration (Buffers) being a free response question? Thanks.</p>