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Topic: AP Chem Kinetics  (Read 4461 times)

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Offline kellyleestb

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AP Chem Kinetics
« on: March 01, 2013, 12:26:25 AM »
Hello

I am stuck on a AP chem kinetics problem. The question is as stated below.

In general, if the temperature of a reaction is raised from 300 K to 320 K, the reaction rate will increase by a factor of approximately

A. 320K/300K
B. 22 degrees celsius/2 degrees celsius
C. 4
D. 2
E. 20

What formula do I use? Do I use the Arrhenius equation?

If it is the Arrhenius equation, how do I calculate the reaction rate?
 
Please respond a.s.a.p! Thank you very much!!!~


Offline Borek

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Re: AP Chem Kinetics
« Reply #1 on: March 01, 2013, 03:22:55 AM »
There is a rule of thumb that says when temperature goes up by 10 °C reactions become approximately twice faster.
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Offline Corribus

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Re: AP Chem Kinetics
« Reply #2 on: March 01, 2013, 09:13:31 AM »
Seems like that rule of thumb is what the question is after, but the opening poster should be aware that it's not a particularly good rule of thumb.  Even under the approximation of Arrhenius kinetics, the amount the rate increases as temperature increases is mediated strongly by the activation energy.

See: http://antoine.frostburg.edu/chem/senese/101/kinetics/faq/temperature-and-reaction-rate.shtml

In short, the question doesn't really provide enough information to answer it, because there's no general answer that truly works.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Big-Daddy

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Re: AP Chem Kinetics
« Reply #3 on: March 07, 2013, 02:27:15 PM »
You should also keep in mind that Celsius calculations - as far as I am aware - need never play a role in chemistry or physics whatsoever. Work in Kelvin!

(e.g. in thermodynamic experiments to estimate heat released, you are measuring change in temperature and it is convenient to use Celsius, but fundamentally it is a better universal approach to always use Kelvin in calculations for science.) Common sense should rule out B or E. To do any more you'll probably need the activation energy (especially if Borek and Corribus say there's no other way), or you can guess via the rule of thumb they suggested above.

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