Need help, Activation energy determination from this reaction. Is this possible?

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Discussion Overview

The discussion revolves around the determination of activation energy (Ea) for a specific chemical reaction involving the reaction of persulfate and iodide ions. Participants explore the feasibility of calculating Ea based on experimental data collected at slightly different temperatures and discuss the implications of temperature differences on accuracy.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes an experimental setup to determine activation energy using rate constants at two temperatures, questioning if this method is valid given the small temperature difference.
  • Another participant expresses skepticism about the reliability of the results due to the minimal temperature difference, suggesting potential errors in measurement.
  • There is a request for information on frequency factors or known rate constants for similar reactions, indicating a lack of available data for the participant's calculations.
  • Participants discuss the independence of experimental errors from the date of the experiment, emphasizing that accuracy is crucial regardless of when the measurements were taken.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the validity of the activation energy calculation due to concerns about measurement accuracy and the small temperature difference. There are competing views on the reliability of the results and the methods used.

Contextual Notes

The discussion highlights potential limitations related to the accuracy of temperature measurements and the availability of frequency factors, which are necessary for calculating activation energy.

Who May Find This Useful

This discussion may be useful for students and researchers interested in chemical kinetics, particularly those exploring methods for determining activation energy and the impact of experimental conditions on results.

himynameis
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Need help, Activation energy determination from this reaction. Is this possible??

i did an experiment, i noted the tempreture and found rate constant.
My friend did the same experiment and she found rate constant and noted the tempreture.. The tempreture differs by one degree. Can i calculate tempreture like this...?

S2O82-(aq) + 2 I-(aq) -->SO42-(aq) + I2(aq)

Friend: K1: 0.0594 at t1: 21oC = 294 K
Ours = K2: 0.06 and t2: 22oC. 295 K


In (0.0594 /0.06) = Ea / 8.314 x ( 1/ 294- 1/295 )
-0.01 = Ea / 8.31 x (1.153x10-5)
Ea= 0.01x 8.31 / 1.153x10-5)
Ea = 7207.28 J/mol

= 7.207 KJ mol

Is this possible?

please help me! :( So for this reaction is the Ea 7.207

I would have done Just used my rate constant and tempreture to wwork out Ea but I don't know the Frequency factor A! I can't find this anywhere...
 
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Your approach looks perfectly sound to me. Not that I believe in the result. 1 deg C is a very low temperature difference, especially for a typical lab thermometer. Think errors/accuracy.
 


Borek said:
Your approach looks perfectly sound to me. Not that I believe in the result. 1 deg C is a very low temperature difference, especially for a typical lab thermometer. Think errors/accuracy.

Really ? This is my friends results it was done on a different day. The only reason I had to use this method was because I did not know frequency factor. Do you know anywhere I can get frequency factors or known rate constants for particular reactions?
 


Borek said:
Your approach looks perfectly sound to me. Not that I believe in the result. 1 deg C is a very low temperature difference, especially for a typical lab thermometer. Think errors/accuracy.

thank you very much for your reply!
 


himynameis said:
Really ? This is my friends results it was done on a different day.

Doesn't matter. Experimental errors don't care about date.

The only reason I had to use this method was because I did not know frequency factor. Do you know anywhere I can get frequency factors or known rate constants for particular reactions?

They are determined with the same approach you just used. No idea where to look for the data - the best approach I know is to go to the chemistry dept library at University and ask librarian for help.
 

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