Find the rate constant, given temperature and activation energy.

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Discussion Overview

The discussion centers around a homework problem involving the calculation of a rate constant for a chemical reaction given its activation energy and the rate constant at a specific temperature. The scope includes mathematical reasoning and application of the Arrhenius equation.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • Joe presents a homework problem involving the activation energy of 38.0 kJ/mol and a rate constant of 1.60 × 10² M-1s-1 at 249 K, seeking to find the rate constant at 436 K using the Arrhenius equation.
  • Joe provides the equation he is using and his calculations, noting that his result of 161.257 is incorrect.
  • Borek points out that Joe's error may stem from using the wrong units for the gas constant R, which should be in J instead of kJ.
  • Joe acknowledges the mistake regarding the units of R and thanks Borek for the clarification.
  • A later post corrects the capitalization of kJ to kJ, indicating attention to detail in unit representation.

Areas of Agreement / Disagreement

Participants appear to agree on the identification of the unit error in Joe's calculations, but the discussion does not resolve the overall problem of finding the rate constant at 436 K.

Contextual Notes

Joe's calculations depend on the correct application of units for the gas constant, which is critical for the accuracy of the results. The discussion does not address any further assumptions or steps that may be necessary to complete the solution.

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Homework Statement



A reaction is found to have an activation energy of 38.0 kJ/mol. If the rate constant for this reaction is 1.60 × 102 M-1s-1 at 249 K, what is the rate constant at 436 K?

Homework Equations



ln\frac{K_{2}}{K_{1}}=\frac{E_{a}}{R}\left(\frac{1}{T_{1}}-\frac{1}{T_{2}}\right)

The Attempt at a Solution



Given:

R=8.314
T1=249K
T2=436K
Ea=160

ln(K_{2})=\frac{38}{8.314}\left(\frac{1}{249}-\frac{1}{436}\right)+ln(160)

Which equals 161.257 which is incorrect. Any clues where I went wrong would be greatly appreciated. Thanks in advance.

Joe
 
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Ah ha! I should have noticed that being that R has units of J not Kj. Thank you very much Borek.

Joe
 
kJ, not Kj...
 

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