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Rich_Insane
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[*] posted on 8-5-2009 at 20:28
AP Exam in Three Days??!?


Hey everybody. I am typing, really, really scared now. So i was studying for my AP Chemistry (I have Bio too) Exam, and I took a look at the sample test. On one page, I could only get 20% of them. That's pretty bad.

Here's what I did not know:

Molten NaCl is electrolyzed at a constant current of 1 A. How long will it take to generate 1 mol of Na metal. How can you do this without a given rate.

Memorizing gas laws. They are easy. I can do it. But I need a good way to memorize them.

The worst of all :( I completely forgot almost everything about atoms. Almost. I forgot: Pi, sigma bonds (what are they), sp3 hybridization, and calculating shape (I found a really good book, but right now, it's just guessing the structure), and quantum numbers, spin values, the quantum stuff.

Enthalpy change

How would you know which solution had the highest boiling point? It gives a list of various salts. (NaOH, HF, Na2SO4, KC2H3O2, NH4NO3)

Acidity and basic constants ka etc. (what are they?)

Finding the rate of an equation (the rate law)

There's a lot more, but I don't just want answers or anything. I just need a way to keep the memory. I studied, but unfortunately my memories been cleaned multiple times... and now the exam is 3 days away. I'm aiming for a 5. I know your jaw is dropping at how stupid I am :D, but I need your help. Any website will help. These books are trash. WOn't ever use them again.


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[*] posted on 8-5-2009 at 21:16


What books? If you don't want them, I'm sure someone here wouldn't mind picking them up.
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Rich_Insane
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[*] posted on 9-5-2009 at 07:29


Study books especially for the AP exam. I got the best there are from the library. I'm going to hold on to them just in case I can't find any other good sources, and I will continue practicing on them.
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[*] posted on 9-5-2009 at 23:40


What does AP mean?
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chemrox
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[*] posted on 10-5-2009 at 01:15


advanced placement



"Ignorance is the Mother of Devotion." — Robert Burton.
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Lambda-Eyde
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[*] posted on 10-5-2009 at 05:44


http://www.chemguide.co.uk

This site has learned me just about everything I know about bonding. :)
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Rich_Insane
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[*] posted on 10-5-2009 at 10:40


I did go to that site. It was pretty good. I got so much info on bonding!. But now the test is.... tomorrow. I still don't have a clue how to do the electrolysis rate, and I need to find a good site for memorizing gas laws and all that entropy. I also need to know the rate equations, but I am looking at a site right now for that.

[Edited on 10-5-2009 by Rich_Insane]

Ok, that site for rate laws was useless. I couldn't understand a thing there.

[Edited on 10-5-2009 by Rich_Insane]
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Saerynide
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[*] posted on 10-5-2009 at 16:39


The NaCl problem is solved by the fact that 1 A is a rate of charge being moved at 1 C/s.



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[*] posted on 10-5-2009 at 20:31


Ok, so one Coulumb per second. How do we relate that to the amount of sodium being produced? How much time till 1 Mol is formed?
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[*] posted on 10-5-2009 at 22:51


Lambda-Eye, the trick there was to pass it off as sarcasam, but the moment's passed.

Play nice people :cool:




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[*] posted on 10-5-2009 at 23:43


The charge of an electron is 1.602176487 × 10-19 C. How many electrons are needed to make a mole of Na from Na+? At a rate of 1 C/s, how many seconds would it take?

Edit:

Btw, there is only one gas law you need to know: PV = nRT. All the others can be derived from PV=nRT because n and R are constant.

[Edited on 5/11/2009 by Saerynide]




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Rich_Insane
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[*] posted on 11-5-2009 at 17:14


I feel so stupid :o I totally knew that.
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[*] posted on 11-5-2009 at 18:46


If you don't know this stuff by now, you won't know it by tomorrow. Get some rest so that the info trapped in your brain can come out when prompted. Try to relax.

Good luck,

O3





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Rich_Insane
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[*] posted on 11-5-2009 at 20:40


Ha ha never mind guys. I took the AP Bio today instead. I will take the AP Chem next year, in 8th grade, since I am lacking proper preparation.
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[*] posted on 11-5-2009 at 22:51


In 8th grade??? I like your ambition, but I think you should wait a bit. Take the AP Chem class first, or at least an intro highschool chem class.

Memorizing this stuff from the Baron's Study Guide will not help - you need to understand it like the back of your hand and be able to do it with your eyes closed to get an easy 5. You know you are prepared when you remember that the mw of Cl is 35.453 and that Fe is 55.85 without looking at the AP periodic table :D.

AP Chem is supposedly the hardest AP exam... Most people don't take it until they are juniors or seniors.

But dont let that discourage you. Getting a 5 is easy (trust me :D). But it doesn't come from memorizing. If you understand the concepts, it's a breeze - you can do the whole exam in half the time and use the remaining time to snooze while everyone else stares at you in contempt :P

Edit: Try practicising with the SAT II Chem - it's easier.

Ah... AP Bio... I wrote until my hand fell off. I contemplated stopping after securing the 5, but decided I should finish the test just out of academic sportsmanship.

[Edited on 5/12/2009 by Saerynide]




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[*] posted on 12-5-2009 at 15:13


AP Bio was the most fail exam ever. Everyone was writing pages and pages but the answer was so simple!


I want to take classes at my local university in high school, because the classes here are crap. I have a professor who's really nice to me who might let me take O Chem Year 1 right now, in 7th grade, but I really, really don't want to considering how bad my memory at chemistry is. I get everything but the atoms and the gasses.

The thing is that my memory fails on me often.... and there are hundreds of different reactions in O Chem.... and if my memory fails on an exam, I'm screwed.

I took a class for the stuff in the AP Exam from an online course. Most boring course ever. It was essentially a slideshow explaining all of this. But I learned a lot of it. The problem is keeping that info inside my head.

[Edited on 12-5-2009 by Rich_Insane]
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[*] posted on 27-4-2010 at 08:55
It's test week again!


Hey guys,

So last year I canceled taking the AP Chem exam because I felt like I didn't know much. So I ended up taking AP Chemistry, and I feel a lot better. But I'm sort of worried; I have serious trouble with math. It's not even funny, I just can't do math. I do fine in Algebra II/Precal, but for some reason when math is really prevalent in a certain chapter of chemistry, I do terribly in that chapter. For example, I do great on acids and bases because it's simple mathematics and formulas; there's not much to remember (I have terrible....TERRIBLE memory), but on reaction kinetics, I just don't get it. Could someone explain how to diffrentiate between different rate laws and their graphs? I'm also wondering just how much thermodynamic I need. I can do Hess's law and BDE stuff easily, but I have issues with more complex matters. Anyways, I just need to know what to do. I'm using the Princeton Review book to study, and I really need to get a 5 on this test.
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[*] posted on 27-4-2010 at 12:06


In what year in school are you? How old are you?



The single most important condition for a successful synthesis is good mixing - Nicodem
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[*] posted on 27-4-2010 at 17:43


True, there are a lot of reactions. But, generally speaking, organic chemistry is simple.

Most reaction are driven by the addition or removal of a small molecule. Often H2, O2, or H2O.

As for Math....Most folks don't understand it, at least not initially. According to my one-time buddy Carl Abrams, folks generally start to grasp the actual implications of the mathematical formulas they have memorized.....Sometime in graduate school!

Carl had devised fairly simple methods of muddling through chemical mathematics. Some of those methods might have been included in his book, which was very well received when it was first published.
A Course in Experimental Chemistry (Hardcover)
by Manus Monroe (Author), Karl Abrams (Author)

There might be a copy lurking in your school library. Also, Amazon has used copies for 8 bucks or so. Haven't actually seen a copy of the book, but Carl had a genius for simplification. The convoluted and complex, became straightforward and easily absorbed under his guidance.

[Edited on 28-4-2010 by zed]
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[*] posted on 27-4-2010 at 20:25


Quote: Originally posted by zed  

As for Math....Most folks don't understand it, at least not initially. According to my one-time buddy Carl Abrams, folks generally start to grasp the actual implications of the mathematical formulas they have memorized.....Sometime in graduate school!
[Edited on 28-4-2010 by zed]


This is exactly the point of my questions to Rich about his age.

I know it is fashionable for high schools to offer AP courses nowdays and to allow students to take college courses in their senior year in high school, but I have often wondered about the sanity of this. My concern is that if the student does not have the physical maturity and experience he really shouldn't be taking these advanced courses. When I ask this question of parents who have such students I usually get replies that indicate he/she is doing OK in the class, so, I guess young people are just smarter today than we were. I've never agreed with that answer.

This parallels the rampant grade inflation of todays high schools where if you don't have at least a 3.895 grade point you are not doing all that well. In my day only 1 or 2 peolpe had GPAs above 3.5. Again, the idea that students are smarter or work harder seems unreasonable.

Sending high school juniors out to calculus summer camp at Johns Hopkins just sounds dumb: just a way for the parents to brag and the college to make money. The students probably detest it.




The single most important condition for a successful synthesis is good mixing - Nicodem
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Rich_Insane
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[*] posted on 27-4-2010 at 20:40



Quote:

This is exactly the point of my questions to Rich about his age.


Huh?


Quote:

I know it is fashionable for high schools to offer AP courses nowdays and to allow students to take college courses in their senior year in high school, but I have often wondered about the sanity of this. My concern is that if the student does not have the physical maturity and experience he really shouldn't be taking these advanced courses. When I ask this question of parents who have such students I usually get replies that indicate he/she is doing OK in the class, so, I guess young people are just smarter today than we were. I've never agreed with that answer.


I'm not even in high school yet. I'm 14 now. They dumbed down all chemistry up till college level. Not just a little, but dumbed down to the point where you spend 3 weeks on chemical formulas. Since chemistry and biology are my favorite subjects, I'd rather not waste time with elementary stuff and be completely unprepared for harder material later. That's why I want to take AP. I am also pursuing some research which will soon require me to apply a lot of biology and a lot of chemistry (it already does). I don't think anyone's smarter than a previous generation; they just dumbed down classes to a terrible point.

I just really hate how linear school is, I'm not a big fan of memorizing tons and tons of information; I like to see the concept and learn formulas on my own.


Quote:

True, there are a lot of reactions. But, generally speaking, organic chemistry is simple.


AP level O Chem is very easy for me. That's not an issue. It's mainly reaction kinetics, thermodynamics, and scary looking redox reaction (which are more than doable, just daunting for me).

I'm not sure if it's the math I don't get. It's more of the amount of math there is, making it so complex to understand. Especially reaction kinetics.
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[*] posted on 27-4-2010 at 21:02


Quote: Originally posted by Rich_Insane  

I'm not even in high school yet. I'm 14 now.
AP level O Chem is very easy for me.

It's mainly reaction kinetics, thermodynamics, and scary looking redox reaction (which are more than doable, just daunting for me).

I'm not sure if it's the math I don't get. It's more of the amount of math there is, making it so complex to understand. Especially reaction kinetics.


Uh, I'd forgotten how young you are. You are obviously very talented/driven.

My point is that learning and understanding math, and doing lengthy calculations, takes much practice and maturity. At least it did for me.




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[*] posted on 27-4-2010 at 21:11


Hmmm... most of reaction kinetics comes down to probability and 1st year calculus. If you can do algebra, the only hard part of calculus is the idea of a limit. Once you wrap your mind around limits or the cookbook rules that apply to limits (I didn't really understand limits until I took a graduate level pure mathematics course - the most terrifying year and, in retrospect, the most valuable course I took in college) a huge amount becomes either remembering a key equation or deducing it on the spot.

Once you have calculus rates become, well, not necessarily obvious, but "simple" matters of calculation. You get a feeling for which forms of equations "look right". A good first year calculus course also teaches you how to handle series of computations like 1/2 + 1/3 + 1/4 + 1/5 with a line or two of equations. The algebra tells you how to solve sets of equations with multiple unknowns by rules which handles problems where multiple reactions are taking place. Calculus (maybe a bit more advanced) tells you how to take those rules and apply them to rates and rates of change of rates and .... all by rules.

Redox is algebra. Juggle the numbers until left charges = right charges = 0. The electrochemical series tells you which reactions go which way giving or taking how many electrons.

I don't know if this helps or not. The most important thing about math is that it all hangs together. If you aren't too stressed, if you know 2/3 of the problem you can often deduce the rest by rules and logic. Sort of like sudoku ;)

[Edited on 28-4-2010 by densest]
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[*] posted on 27-4-2010 at 22:05


"1 + 1/2 + 1/3 + 1/4 + 1/5", mentioned above, the "harmonic series" is a DIVERGENT series, with no finite sum as the number of terms approaches infinity; although it diverges very slowly, with the sum of a million terms being less than 20. It is, however, related to the logarithmic function, with the sum to N terms approaching, with increasing terms, ln(N) - y where y = Euler's constant = 0.57721 56649 01532 86060 65120 90082 40243 10421 59335 93992 ... approx.
This approximate sum to N terms is, of course, the finite-difference equivalent of the integral of the function 1/x from 0 to N = ln(N) + constant of integration.
See: http://en.wikipedia.org/wiki/Euler%E2%80%93Mascheroni_consta...

However, noting also the relationship to the Riemann zeta function, if the terms in this series are replaced by any power of the same terms greater than 1, it becomes absolutely convergent as the zeta function, with the sum decreasing with increasing such power.

If the terms are all multiplied by (-1)^(N+1), so that the terms alternate in sign, the series becomes "conditionally convergent", in this case with a sum of ln(2) = 0.6931...., which is a consequence of Taylor's Theorem from which the series for natural logarithms ln(x) is derived. Alternating signs also result in convergence if the terms are raised to any positive power, although the convergence is "conditional" for powers less than 1.

[Edited on 28-4-10 by JohnWW]
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[*] posted on 28-4-2010 at 20:07


Well for me it's not really the essence of the math that bothers me; It's the complexity of the process that is required. I did look into reaction kinetics. Turns out that I was probably overreacting about how little I know on it. I just can't find a solid way to find exponents in the rate law. How would one do as such? Isn't it something like (change on concentration)^(order; the x) = (change in rate)? I have terrible, terrible attention span, so that's why things like long mathematical process trouble me. I tend to wander off in the middle of a long process.

I know I could just look this up in my textbook, but what exactly does H+ addition in a reaction do (as well as OH-)? I know the fact that you form water somehow, is it to balance out water or something?
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