Does Stirring Increase Accuracy of Rate Law Calculation?

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Discussion Overview

The discussion revolves around the impact of stirring on the accuracy of rate law calculations in chemical reactions. Participants explore whether increased reaction rates due to stirring lead to more accurate determinations of rate laws, considering factors such as concentration distribution and reaction kinetics.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that stirring could increase accuracy in rate law calculations by allowing for faster reaction rates, which may better reflect initial concentrations at a specified temperature.
  • Another participant notes that rate laws assume the activity of reactants is approximately equal to their concentrations, particularly at low concentrations and temperatures, and suggests that stirring helps achieve uniform distribution of reactants.
  • A further response questions the necessity of uniform distribution, indicating a lack of understanding of its importance in relation to reaction rates.
  • Another participant raises a hypothetical scenario comparing reaction rates in uniformly distributed reactants versus stratified reactants, emphasizing that the rate law applies locally.
  • One participant reiterates the concern that non-uniform concentrations could lead to varying reaction rates throughout the solution.

Areas of Agreement / Disagreement

Participants express differing views on the necessity and impact of stirring on reaction accuracy, with some supporting its benefits for uniformity and others questioning its importance. The discussion remains unresolved regarding the extent to which stirring affects rate law accuracy.

Contextual Notes

Participants have not fully explored the assumptions underlying the relationship between stirring, concentration uniformity, and reaction rates. The discussion includes hypothetical scenarios that may not account for all variables involved in rate law calculations.

Macroer
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An experiment was done by me to determine the rate law of a reactant. If the reaction occurred faster(ex. by just stirring reactants), would the accuracy of rate law calculated increase? If it doesn't increase accuracy, then what is the point of stirring/swirling the reactants?

I think that the accuracy would increase, because the rate law is most accurate for the initial concentrations at an specified temperature, and this changes more throughout a longer experiment, than a shorter one. So a faster experimental rate of reaction would increase the accuracy. Need some confirmation. Thanks.
 
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The rate laws using concentrations assume that the activity of the reactants are approximately equal to their concentrations, which is a fair assumption at low concentrations and temperature.

Regarding your question about stirring, it might be useful to have the rectants uniformly spread throughout the container.
 
espen180 said:
The rate laws using concentrations assume that the activity of the reactants are approximately equal to their concentrations, which is a fair assumption at low concentrations and temperature.

Regarding your question about stirring, it might be useful to have the rectants uniformly spread throughout the container.

Right, i don't understand why it needs to be uniform.
 
In which situation do you think the reaction A+B->C will proceed faster, given the rate law r=k[A]. Remember that the rate law applies only locally.

1) A and B uniformly distributed throughout the container.

2) A on the bottom and B on the top, with smaller region in between where they are mixed.
 
Macroer said:
Right, i don't understand why it needs to be uniform.

If the concentrations of the reactants vary at different points in the solution, then the reaction rate will also not be the same at all points in the solution.
 

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