Integrating a concentration profile

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Discussion Overview

The discussion revolves around integrating a diffusion profile to determine the increase in mass of a sample based on concentration versus distance. Participants explore the relationship between concentration, mass, and the implications of integrating the diffusion profile.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about how to relate the integrated diffusion profile to the overall mass of the sample.
  • Another participant questions the relationship between concentration and mass, emphasizing that "moles" is not a concentration.
  • A participant clarifies that their diffusion profile is based on an initial amount of substance in moles plotted against distance, seeking to understand the implications of integrating this profile.
  • Concerns are raised regarding the meaning of "moles" as a function of distance, with one participant stating that it is meaningless unless it represents the total amount of substance over a specific range.
  • It is noted that concentration is typically expressed as moles per unit volume, and the integral of concentration would yield moles per unit area, suggesting a need to multiply by cross-sectional area to find total moles.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of concentration and mass in the context of the diffusion profile. There is no consensus on how to interpret the integration of the profile or its relevance to the overall mass of the sample.

Contextual Notes

There are limitations regarding the definitions of concentration and the dimensionality of the diffusion process that remain unresolved. The discussion also highlights the need for clarity on the relationship between moles, concentration, and mass.

DiffusConfuse
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Hello-

I have a diffusion profile, in which I plot the decrease in concentration versus distance of my sample. I am trying to find the increase in mass of the overall sample. How would I do this?

I have integrated the function and am wondering what type of information that would supply my. Units would be concentration*distance. moles*m
 
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How are concentration of something and "mass of the overall sample" related?
If your diffusion (and concentration) is not one-dimensional, you should consider this in the integral.
"Moles" is not a concentration.
 
I did not actually plot the concentration. My diffusion profile consists of an initial amount of substance a in moles n(a) and plots it as a function of distance in the sample. so I am trying to figure out what information I get when I integrate this profile. moles*meters would be the units
 
Again, "moles" is not a concentration. Moles as a function of distance are meaningless, unless it means the total amount of substance between that point and some other point. In that case, I don't see any application of the integral.
 
Concentration is usually expressed as moles per unit volume (e.g., moles/cc). The integral of this is moles/cm2. To get the total number of moles in the sample, you then need to multiply by the cross sectional area of the sample.
 

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