Can I Use Rates Instead of Rate Constants in an Arrhenius Plot?

  • Thread starter Thread starter mycotheology
  • Start date Start date
  • Tags Tags
    Arrhenius Plot
Click For Summary

Discussion Overview

The discussion revolves around the application of the Arrhenius equation in the context of determining shelf life in chemistry. The participant is exploring whether rates derived from percentage changes can be used in place of rate constants in an Arrhenius plot.

Discussion Character

  • Homework-related, Technical explanation

Main Points Raised

  • One participant presents a scenario involving the need to calculate activation energy (Ea) and the pre-exponential factor (A) using the Arrhenius equation but lacks the necessary rate constants (k).
  • The same participant proposes using calculated rates from percentage changes at different temperatures instead of the rate constants.
  • Another participant suggests that with two data points and two unknowns, it is possible to solve for both Ea and A using simultaneous equations.
  • A follow-up response confirms the suggestion of using simultaneous equations to find the unknowns.

Areas of Agreement / Disagreement

Participants appear to agree on the feasibility of using simultaneous equations to solve for the unknowns, but there is no consensus on the appropriateness of using rates instead of rate constants in the Arrhenius plot.

Contextual Notes

The discussion does not address the assumptions behind using rates in place of rate constants, nor does it clarify the implications of this substitution on the accuracy of the results.

mycotheology
Messages
86
Reaction score
0
Heres the question:
http://img215.imageshack.us/img215/1185/screenshot5xq.png
Kinetics is probably my weakest area in chemistry so I'm struggling. To find the shelf life, I need to use the Arrhenius equation but I don't know the activation energy Ea or the A constant. So I converted 2 those percentages into rates and got:
At 40C, rate = 0.082 %/month
At 60C, rate = 0.39 %/month
I know that if I plot 1/T vs. lnk, I get an Arrhenius plot and then I can find Ea from the slope and A from the y-intercept but I don't have k. Can I just use the rates that I have instead of k?
 
Last edited by a moderator:
Chemistry news on Phys.org
You have two data points and two unknowns, that means you should be able to find both solving system of two equations.
 
Can you elaborate on that a bit. Do you mean use simultaenous equations?
 
Yes.
 

Similar threads

Arrhenius Equation: Can We Substitute k with 1/t?
  • · Replies 3 ·
Replies
3
Views
3K
Relationship between ln k and 1/t using different formula
  • · Replies 2 ·
Replies
2
Views
9K
Determine Activation Energy from rate?
  • · Replies 2 ·
Replies
2
Views
4K
Rate constant calculation Using the Arrhenius equation
  • · Replies 1 ·
Replies
1
Views
3K
Understanding Arrhenius Plots: ln(rate) vs 1/T for Determining Activation Energy
  • · Replies 1 ·
Replies
1
Views
2K
Chemistry Finding rate constant from pressure change in an experiment
  • · Replies 2 ·
Replies
2
Views
2K
Solving Kinetics & Arrhenius Equation: Find A & Ea
  • · Replies 1 ·
Replies
1
Views
3K
Calcualting Activation Energy using Arrhenius equation and plot
  • · Replies 2 ·
Replies
2
Views
3K
Why is the Arrhenius plot for the rate constant different from y=e-1/x?
  • · Replies 9 ·
Replies
9
Views
8K
Calling kinetics experts: rate law from conductivity isnt possible?
  • · Replies 3 ·
Replies
3
Views
3K