A- pre-exponential factor

Arrhenius Equation:

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cassidysong 1K
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A- pre-exponential factor

Postby cassidysong 1K » Fri Mar 13, 2020 11:56 am

I know what A represents however I am confused by how you calculate A?

Diana A 2L
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Re: A- pre-exponential factor

Postby Diana A 2L » Fri Mar 13, 2020 12:09 pm

Using the Arrenhius equation, take the natural log. Then you get ln k =-Ea/R (1/T) + ln A. From here, exponentiate, then divide to solve for A. You get A= k/ (e^-Ea/RT), Now to calculate A, you need to know R, T, Ea, and k. We know R, we probably know T, and k, even if it’s not already given, you can calculate using a rate law. Activation energy would have to be given to get A. Hope that helps.

Dina Marchenko 2J
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Joined: Thu Jul 25, 2019 12:16 am

Re: A- pre-exponential factor

Postby Dina Marchenko 2J » Fri Mar 13, 2020 3:08 pm

A is found by the arrhenius equation k=Ae^-Ea/RT. If you are asked to find A, you will be provided the information to plug in the values for all other variables in the equation. So basically, you'll end up dividing k by the term e^-Ea/RT (or the subsequent number value you get) to isolate A on one side.


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