Official 2011 AP Chemistry Thread

Test Preparation AP Sciences
901

<p>Got’cha, skateme.</p>

<p>I recently saw this one on 2010 B FR:
Ni2+ + 6NH3 -> [Ni(NH3)6]2+</p>

<p>I’m guessing the “doubling the charge” doesn’t happen here, since it’s the same.
And uh, why did they choose 6 and put it only on the ammonium? I would have chosen 4 (just because for some reason I think the doubling affects not only the charge but also the subscript?) and put it outside the bracket.
Also did they stop giving points for incorrect complexes? There isn’t an additional thing that says “Orrr you can get points for _____ another one.”</p>

<p>Good luck, G0DZILLA&skateme!</p>

902

<p>Good luck guys!</p>

<p>I think that it can be either 4 or 6…strange they didn’t put that. But since they had it last year, we’re probably not going to get a complex ion question so don’t worry.</p>

903

<p>Really?
Awesomee.
Any idea why they put the 6 inside the square brackets though?</p>

904

<p>That’s just notation, it’s not that important. It’s because the 6 shows you have 6 molecules of NH3, but the brackets on the outside shows that the molecule has an overall charge of 2+.</p>

905

<p>All right, thanks.</p>

<p>Okay so I googled it.
Galvanic cells have the electron flow from the anode to the cathode.
Electrochemical ones have it from the cathode to the anode.
Not sure why though. . .</p>

906

<p>Just checking on this one, but does adding reactants to a galvanic cell increase or decrease the voltage?</p>

907

<p>Because Ni2+ can form 6 ligands. Hence, there are 6 ammonias in the complex molecule. Since ammonia had no charge to begin with, nickel’s charge of 2+ is the one that shows through. </p>

<p>10 minutes until I head out!</p>

908

<p>Uh oh. I have never heard of anything like that, i.e. I haven’t heard of adding reactants.</p>

909

<p>chewydog, same here! You think you can answer my question though? I think it has something to do with L’chatlier’s principle…</p>

910

<p>Increase due to LCP, but not when extra solids are added (K value)</p>

911

<p>Wait, this seems dumb, but what’s LCP?</p>

<p>Edit: NVM LOL got it! ;)</p>

912

<p>Oh no, what’s LCP? xD</p>

<p>Also Ni2+ can form 6 ligands . . . that’s a memorizable fact, I assume?
Are there any other common ones?</p>

913

<p>L’chatlier’s principle =LCP! Lol don’t worry I was confused too xD</p>

<p>Usually, you can guess 6 or 4. I think you double the charge on the ion and that’s the number of ligands…</p>

914

<p>Alright guys, I’m heading out! See you here after my 2 exams =.=</p>

915

<p>Oh okay.</p>

<p>Uhhh isn’t Mercury II the one with a 1+ charge and Mercury 1 with a 2+ charge?!</p>

<p>Good luck, Bioboy!</p>

916

<p>Good luck to everyone again! </p>

<p>I’m getting ready to go. But here’s the answer to your question: (Hg2)2+ is mercury I, each Hg has 1+ charge. Mercury II is Hg2+</p>

917

<p>I Just finished the exam. I hope I did well on it.</p>

918

<p>Well… so? How did everyone do?</p>

919

<p>i didnt think the multiple choice were too bad, but the free response was rather difficult. when are we allowed to start discussing the exam?</p>

920

<p>idk, yea FR was really bad. I did okay-ish on MCQ though.</p>