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Topic: Half life/ instantaneous rate problem  (Read 3600 times)

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Offline Korokian

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Half life/ instantaneous rate problem
« on: March 06, 2007, 06:10:53 PM »
The half-life of a first order reaction is 140s.  What is the instantaneous rate of the reaction when the reactant concentration is 0.19M?

I am clueless on how to start this.... help would be appreciated.
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Offline Yggdrasil

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Re: Half life/ instantaneous rate problem
« Reply #1 on: March 07, 2007, 01:12:25 AM »
Can you write an expression for the concentration of your reactant as a function of time?
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Offline Korokian

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Re: Half life/ instantaneous rate problem
« Reply #2 on: March 07, 2007, 03:45:55 PM »
i don't know how to write the function but what i do know is the initial concentration is halved after 140 seconds

i figured out k in t1/2=ln2/k

140s=ln2/k
k=.00495

and rate=k[A]

rate=.00495 x .19
rate= 9.41 x 10-4?
« Last Edit: March 07, 2007, 04:02:58 PM by Korokian »
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Offline Yggdrasil

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Re: Half life/ instantaneous rate problem
« Reply #3 on: March 07, 2007, 04:33:43 PM »
Looks right to me.  Good job.
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Offline Korokian

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Re: Half life/ instantaneous rate problem
« Reply #4 on: March 07, 2007, 05:22:39 PM »
Thank You!
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