Calculating Activation Energy Using Slope and the Arhennius Equation

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Discussion Overview

The discussion revolves around the calculation of activation energy (Ea) using the Arrhenius equation and the method of linearization involving temperature and rate constant (k). Participants explore the relationship between the slope of a linear plot and the activation energy, as well as common practices in plotting data for this purpose.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about applying the Arrhenius equation and the linearization process.
  • Another participant clarifies that the method described is a standard approach for linearizing exponential laws.
  • A participant notes that the slope of the linear plot will be negative, indicating that the activation energy must be considered as a positive value.
  • There is a suggestion that when discussing the slope, it should be emphasized that Ea is the absolute value of the slope multiplied by the gas constant R.
  • One participant mentions an alternative approach of using 1/RT or β for the x-axis when dealing with numerical values instead of moles.

Areas of Agreement / Disagreement

Participants generally agree on the method of linearization and the interpretation of the slope in relation to activation energy, though there are nuances in how to express these relationships and the constants involved.

Contextual Notes

There are mentions of strictness in definitions and the need to clarify the relationship between the slope and the gas constant, indicating potential assumptions that may not have been fully articulated.

relativitydude
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For some reason, this isn't working out.

The Arhennius equation, k = A*e^(-Ea/RT)

I have tables of temperature and k. The book says just calculate it by having the x-axis be 1/T and y-axis be ln(k)

Ok, take Ln of both sides
ln(k) = ln(A*e^(-Ea/RT))
ln(k) = -Ea/RT + ln(A)

Oh, that looks like y = mx + b
 
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So there's actually no problem.It's a standard way of linearizing exponential laws...

Daniel.
 
Ya, I was just being stupid.
 
Note that Ea will be the absolute value of the slope. The slope will be negative, Ea must be positive.
 
Gokul,if you wanted to be strict,u should have mentioned that Ea is the absolute value of the slope TIMES THE GAS CONSTANT "R"...

Daniel.
 
dextercioby said:
Gokul,if you wanted to be strict,u should have mentioned that Ea is the absolute value of the slope TIMES THE GAS CONSTANT "R"...

Daniel.

I should have.

It's common to make the x-axis 1/RT or [itex]\beta[/itex] (when dealing with numbers instead of moles).
 

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