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Re: Chem Lab C

Posted: January 26th, 2013, 4:50 pm
by Skink
And it isn't really easily self-taught. It's hard enough when taking the class...

Re: Chem Lab C

Posted: January 26th, 2013, 7:03 pm
by 135scioly
Will we be required to know how to do any lab tests for this event? Like titration? Thanks :)
You are required to know how to do labs, but the procedure is usually outlined by the supervisor...I don't think that something like a titration would be practical for a 50-minute time block (and it doesn't really relate to the topics this year). So far, I have seen two fairly easy equilibrium labs and one very easy periodicity lab. Speaking of which, you CAN anticipate having one lab for equilibrium and one for periodicity (this happened at Athens and possibly elsewhere). And I agree, @Skink, an AP Chem book is incredibly useful to learn stuff, just know that (at least in the one for my AP Chem class), equilibrium takes up several lengthy chapters.
What do you mean by a periodicity lab? What kind of lab would that be?
And it isn't really easily self-taught. It's hard enough when taking the class...
Haha, well then I have my work cut out for me! :)

Re: Chem Lab C

Posted: February 11th, 2013, 8:22 pm
by milka
Does anyone know what "Us[ing] a calorimeter to predict a curve" means as far as this event goes? Would that just be like...a temperature curve? Or sometting else? I'd assume the latter, since the topic is equilibrium, however, I'm not familiar with using thermo in an equilibrium context. Could somebody please point me in the right direction?

Re: Chem Lab C

Posted: February 11th, 2013, 9:07 pm
by Skink
Good question. The thing that directly links K to thermodynamic parameters that I know of is the van 't Hoff equation (it's fun to say and...not much else), like the van 't Hoff factor you find with colligative properties. If not this, the thing is that combustion reactions tend not to be reversible ;), so I'm not sure what other overlaps equilibrium can have with calorimetry, myself.
Here's the equation in log form:
Image
I...don't think it's this (EDIT: second thought, it's definitely not this...it's way too high level even in Science Olympiad). It could just be referring to thermal equilibrium and asking you to plot temperature versus time. That seems more doable. I dunno; I'm gonna think about this a bit...

I plan to populate the Wiki page when I have a chance, so I, too, would like to hear thoughts on what everyone thinks this one refers to seeing as how I'm unsure.

Re: Chem Lab C

Posted: February 19th, 2013, 8:38 am
by labchick
At my Regionals, titration was a part of the test. My partner and I hadn't spent a lot of time on it because we didn't think it would be on the test. What other labs have any of you had for equilibrium/ perdiodicity so I can be prepared for States?

Re: Chem Lab C

Posted: February 19th, 2013, 8:48 am
by EastStroudsburg13
Titration is probably one of the most common labs for equilibrium. It's even cited on the rules... :?

In terms of periodicity labs, I haven't had many, but I think one was looking at precipitation reactions, like what precipitates out and what doesn't.

Re: Chem Lab C

Posted: February 19th, 2013, 9:33 am
by 135scioly
At our regionals, the whole test was made up of two labs. One was equilibrium where you added different concentrations of certain solutions to a control test tube, and compared the reaction, so which way the equilibrium shifted to. The other one was where we were given five unknown substances and we had to use flame tests and solubility to figure out what they were, so I guess that one was a periodicity one.

Re: Chem Lab C

Posted: March 3rd, 2013, 9:42 am
by 3nv1r0nm3ntal ch3m
Reading the rules yesterday, I noticed that the two topics are periodicity and equilibrium. Does anyone else think these seem like very narrow topics?

Re: Chem Lab C

Posted: March 3rd, 2013, 10:14 am
by FullMetalMaple
To an extent, maybe, but equilibrium can also include such topics as acids and bases and solubility. It really depends on what test writers choose to do with it.

Re: Chem Lab C

Posted: March 3rd, 2013, 11:34 am
by 3nv1r0nm3ntal ch3m
To an extent, maybe, but equilibrium can also include such topics as acids and bases and solubility. It really depends on what test writers choose to do with it.
But even that isn't that complex if you know how to do it. And solubility is just memorization of a few salts.