Official AP Chemistry Thread (2014-2015)

Test Preparation AP Sciences
921

Okay honestly I think the only thing we really need to worry about is TEMPERATURE, as far as rate constants are concerned. Rate of reaction can by changed by concentration, temp, all that stuff. Correct?

Kc=equilibrium constant

Kc= [C]^c[D]^d / [A]^a[ B]^b

If K>1 then equilibrium favors products
If K<1 then equilibrium favors the reactants

rate=k[A]^a[ B ]^b
k=rate constant

ok so this might be useless for some of you but I got a little confused with the K and k and this helped me anyways so yea ok

922

@Frigidcold It is possible to GRIND a solid, Change particle size (if solution, both based on nature of solution and temperature and less so pressure). For gases, particle size is less difficult to change.

923

@Mathman97 - I’m talking about a pill dissolving in a solvent like water.

924

Just took the 2014 MC in the past hour and got a 42/50 with 20 mins left to spare… I honestly thought that the 2014 was much easier than the 2013 lol but hopefully its that easy tomorrow because the only ones I got wrong were stuff that were too deep or that I didn’t cover :smiley: That’ll leave me a good spot to get a 5 but I’m aiming for a 4 so thank god

925

bro this is middle school science, crushing is a physical change, its the same molecule, just more surface area

926

Arrhenius equation defines 'k = Ae^(-Ea / RT). If a catalyst lowers the activation energy, the rate constant increases.

927

Wow. So many people are so lost. Good luck tomorrow. Also, as a word of advise, I would trust sources other than the people here, or you’ll miss more than you would’ve

928

Just as a side note, rate constant goes UP when Ea goes down. Do the math

929

Are you low-key trying to say we’re all going to fail here or @andyis

930

Please, link me a problem where they ask about grinding a solid >.>

@SippinCoffee Agreed.

931

@ andyis Yeah, that’s established :stuck_out_tongue:

932

Someone please explain 17 and 20 on 2014!!!

933

Someone please explain 17 and 20 on 2014!!!

934

i think at this point, we should quit studying btw, lets all relax and sleep

935

@SippingCoffee - LOL
Also, I like your username :stuck_out_tongue:

936

If you guys are still discussing the rate constant here’s this from the Princeton Review:

“If the reaction is moving faster, the slope of any line graphing concentration vs. time would be steeper. This increases the magnitude of the slope, and thus, increases the magnitude of the rate constant as well.”

So anything that changes the rate of the reaction will change the rate constant too.

937

Agreed.

938

[A] and B are the concentrations of substances A and B in moles per volume of solution assuming the reaction is taking place throughout the volume of the solution. (For a reaction taking place at a boundary one would use instead moles of A or B per unit area).
http://en.wikipedia.org/wiki/Reaction_rate_constant

increasing the surface area DOES increase the value of [A] and B, it’s just represented differently because solids don’t really have a “concentration”

in other words; for non-solutions, generally represents an amount of reactant present for the reaction to occur.

Also:
http://chemistry.stackexchange.com/questions/9247/changes-in-which-factors-affect-both-the-rate-and-the-rate-constant-of-a-first-o

939

It’s only 6:01 pm here in California.

940

@APScholar18 For #20, you literally just look at the chart.