I don't suppose any of you motherfuckers are experts on electrochemical cells?

[insertnamehere]

I'm offering sexual favors to anyone that helps me pass chemistry.

[adam_f]

Well, calling me a motherfucker won't help you out in the least.

[insertnamehere]

edit : I decided this post was inappropriate for the board.

Suffice it to say that I love you all and would appreciate any help you could offer. <3

My apologies if this was horribly offensive to anyone.

[cookiepuss]

if you offer sexual favors to your professor you'll have a better chance of passing, instead of offering them to twats like us.

(y)

nothing wrong with fucking for grades, I always say...;)

[milleson]

Erm, what's your question exactly?

[insertnamehere]

I thought about being a little more friendly with my lab TA that's grading exams, but then I found out he grades the R-Z's and I'm an H. Not sexual friendly, just flirty. Make sure he knows who I am and that I'm cute and shit, you know?

Anyway, I have numerous questions, but for starters, how do I work something like this?
------------------
What is the cell potential of the following cell at 25C? Note Au is a passive electrode

Cu / Cu^2+ (0.00260 M) // Cr^3+ (0.730 M), Cr2O7^2- (0.0460), H^1+ (1.00 M) / Au

[insertnamehere]

I failed Chem 101 twice and got a D in it the third time. In retrospect, I'd have sucked some dick for that class.

[milleson]

The first thing you need to do is write the equation(s) as half reactions, then decide how many electrons are being transferred.

[insertnamehere]

Ok, so I've got

Cu^2 + e-1 <=> Cu^1..... E=0.16v
Cr2O7^2- + 14H + 6e-1 <=> 2Cr^3 +7H2O..... E=1.33v

I'm guessing then I need to do something with the molarity but I don't know exactly how to deal with that

[milleson]

Remember that the Nernst equation takes into account the concentrations of electrons being transferred. Have you guys discussed the Nernst equation? Presumably you would have seen it in some form or another if this is one of your homework problems.

[milleson]

Don't cheat! (http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/electrode.html) Read that page and see if it makes sense. They even have a little calculator for solving these types of problems. For checking your work, of course.

[insertnamehere]

so I'm wanting to use

E = (RT/n) * log ([C]^c[D]^d / [A]^a[B]^b)

R and T are straightforward. Normally n is number of moles but that doesn't seem to be applicable here and then I'm not sure how to find the concentrations of A-D. I'm thinking A and B are Cu^2 and Cr2)7^2- and C and D are Cu^1 and 2Cr^3 but I'm not sure, and then the a,b,c,and d are the coefficients, which would leave me with

(RT/n) * log ([Cu][Cr]^2 / [Cu][Cr2O7])


Also, geology, nice. I thought about going into geology, but I can't seem to pass stuff like this, which is kind of a deterrent.

[insertnamehere]

Don't cheat! (http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/electrode.html) Read that page and see if it makes sense. They even have a little calculator for solving these types of problems. For checking your work, of course.

ah, danke. I was typing my previous response and hadn't seen this yet.

[insertnamehere]

This actually looks really helpful. The title of my homework that's due tonight (one of them) is "Nernst Equation" actually, but I can't find it in the book anywhere. Our book sucks. A lot.

Chemistry makes me feel retarded :(

[cosmo105]

wait till you get to ochem.

[insertnamehere]

I heard ochem is like, memorization, which I can do. This Qchem is bull though. I can't do chemistry and I can't do math and I sure as hell can't do chemistry math.

I tried using that calculator and I still can't get the right answer. I have no idea what's going on with any of this stuff :(

[milleson]

btw, huge difference between log and ln

Make me some Rice Krispy treats and I will tutor you in chemistry.

It seems like you are on the right track. Somewhat. Remember Q is always expressed as "products over reactants". This is one of my mantras. Anywho, Q=([C]^c[D]^d)/([A]^a[B]^b)

The letter in brackets, [X], is the molarity expressed in the problem. The small letter in the exponential, x, is the stoichiometric coefficient of the balanced equation. It looks like you kinda made it that far.

Did you determine how many electrons, n, are being transferred?

[insertnamehere]

I guess I'm having problems with that I can't figure out how to write the net rxn from the half reactions, making any further steps pretty much entirely impossible.

I have homeworks on the nernst equation and electrolysis tonight, and then rate laws and reaction mechanisms due tomorrow night, and then integrated rate laws and arrhenius behavior over the weekend, and my exam is Monday morning, and we just finished up electricity stuff and started talking about rate of reaction stuff today. I have no idea how I'm actually going to pass this.

I'll make you a million rice krispie treats if you come here and spend the weekend with me working on chemistry the whole time. Well not the whole time. I work some tomorrow and saturday too (n)

And there's still the potential for sexual favors.

[milleson]

Sounds intense. Perhaps taking chemistry in the summer semester may not be the wisest choice. Does your campus have a tutoring center of any kind?

[insertnamehere]

They do, but its Mon and Weds from 11-2. Incedentally that's like the only time I can get any hours at work so I haven't been able to go any. So the final is Monday and I get a week off, and then I start a different class on analytical chemistry. I don't even know what analytical chemistry is.

Also this teacher is supposedly really incredibly hard.Everyone I know that's had this class told me not to get this guy and he's the only one that teaches it during the summer, and I was told I have to take these things over the summer to stay on track. If I fail it could push my graduation back A YEAR. So yeah.

Also, everyone I know who's taken this class before has refused any attempt I've made at asking them any kind of question about it. Hmph.

[insertnamehere]

6 electrons!

still working on the equation though.

[insertnamehere]

gah, i used up all my submissions for that problem. i coudln't get it. on to the entire rest of my homework that i have an hour left to do