Why Did My Reaction Order Deviate in Chemical Kinetics Lab?

Click For Summary
SUMMARY

The discussion centers on a chemistry lab experiment involving the reaction of NaOH 0.03M and methyl violet, where absorbance was measured using a spectrophotometer. The calculated rate constants were k' = -0.1647 for the first solution and k' = -0.4022 for the second solution, leading to an unexpected reaction order of a = 1.74 instead of the expected a = 1. The deviation in results is attributed to a potential miscalculation in the NaOH concentration, as the participant suspects the second experiment used a 0.07M concentration instead of the intended 0.05M. This indicates that the reaction order may not solely depend on the concentration of one reactant.

PREREQUISITES
  • Understanding of chemical kinetics and reaction orders
  • Familiarity with spectrophotometry and absorbance measurements
  • Knowledge of molarity and dilution calculations
  • Ability to interpret and manipulate kinetic equations
NEXT STEPS
  • Review the principles of chemical kinetics and reaction order determination
  • Learn about the use of spectrophotometers in measuring reaction rates
  • Study the impact of concentration on reaction kinetics
  • Explore common errors in laboratory experiments and how to avoid them
USEFUL FOR

Chemistry students, laboratory technicians, and educators involved in chemical kinetics and experimental design will benefit from this discussion.

sergey_le
Messages
77
Reaction score
15
TL;DR
tring to understand what went wrong when i did an experiment
last week i did a chemistry lab. i mixed NaOH 0.03M with equal part of methyl violet and mesured aborbance in a spectrophotometer. then i did the same thing with a 0.05M and methyl violet
i did today the graphs and got the k' =-0.1647 for the first solution and k'=-0.4022 for the second solution.( k'= k * OH conentration )
i was told to use the equation in the attached file. from what i understood the equation gives the reaction order and the instructor said we should get a=1.so i should get from this that only one reactent effects this reaction?
when i plug in my numbers i get a=1.74.
can anyone explain me the meaning of the equation , and what my result means? i guess that i didnt delute my NaOH wuth enough water and did the second expiement with 0.07M consentration instead of 0.05M (since if i put it in the equation instead of 0.05 iget a=0)
 

Attachments

  • פורום.png
    פורום.png
    5 KB · Views: 276
Last edited by a moderator:
Chemistry news on Phys.org
What is the reaction involved? Tell us about the data and how you reduced it.
 

Similar threads

Mass balance with reaction -- Chemical kinetics POV
  • · Replies 4 ·
Replies
4
Views
3K
Chemical Kinetics QuestionDetermination of order of reaction
  • · Replies 1 ·
Replies
1
Views
3K