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Topic: Kinetics question  (Read 2579 times)

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Offline kirushanth

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Kinetics question
« on: November 08, 2012, 01:42:47 PM »
Consider the simple reaction A+2B ---> Products. If we double the volume of the vessel where this reaction takes place, how will the rate of disappearance of B get affected?

Offline curiouscat

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Re: Kinetics question
« Reply #1 on: November 08, 2012, 02:09:24 PM »
1/8 assuming they are gases.

Offline juanrga

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Re: Kinetics question
« Reply #2 on: November 10, 2012, 11:21:31 AM »
The ordinary rate is
[tex]R = k [A] [ B ]^2[/tex]
or, equivalently,
[tex]R = k \frac{n_A}{V} \left( \frac{n_B}{V} \right)^2 \propto \frac{1}{V^3}[/tex]
Therefore for reactions in different volumes
[tex]\frac{R´}{R} = \left( \frac{V}{V´} \right)^3 [/tex]
if [itex]V' = 2V[/itex] we obtain the 1/8 mentioned by curiouscat
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Offline adianadiadi

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Re: Kinetics question
« Reply #3 on: November 12, 2012, 11:08:53 AM »
Unless we know the orders with respect to each term in the rate equation, it is not possible to tell what will happen exactly.

Offline curiouscat

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Re: Kinetics question
« Reply #4 on: November 12, 2012, 01:17:39 PM »
Unless we know the orders with respect to each term in the rate equation, it is not possible to tell what will happen exactly.

With only the given info. fair to assume its an elementary reaction....

Offline juanrga

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Re: Kinetics question
« Reply #5 on: November 12, 2012, 03:18:19 PM »
The original poster says that it is a "simple reaction" and this is sometimes used as synonym of elementary reaction {*} in whose case the orders are known.

{*} http://www.chem.arizona.edu/~salzmanr/480a/480ants/reacmech/reacmech.html
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