Convert Mol/cm3 to PPMV: Pressure & Temp Considerations

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Discussion Overview

The discussion revolves around converting concentration from mol/cm3 to parts per million by volume (ppmv), with considerations of pressure and temperature. Participants explore the definitions and implications of these units, particularly in the context of gases.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant requests guidance on converting mol/cm3 to ppmv, specifically mentioning the need for pressure and temperature information.
  • Another participant questions the meaning of "ppmv," suggesting it stands for "parts per million by volume," and seeks clarification on the "v" aspect.
  • A third participant provides a definition of ppmv, indicating that it involves multiplying by 1.0e6.
  • Discussion includes a reference to the standard usage of ppmv with gases, with links to external resources for further information and sample calculations.
  • One participant expresses skepticism about the conversion, stating that the dimensional analysis shows a difference between mol/cm3 and ppmv.
  • A later reply introduces a formula for calculating ppmv based on gas density and air density, indicating a method to approach the conversion after converting to SI units.

Areas of Agreement / Disagreement

Participants exhibit a mix of agreement and disagreement. While some provide methods and definitions, there is contention regarding the feasibility of the conversion and the appropriate context for using ppmv.

Contextual Notes

Participants note the importance of dimensional analysis in the conversion process and the potential limitations when applying the term ppmv outside of gas contexts.

sneez
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I need to convert mol/cm3 into ppmv

how would i go about that if i know pressure and temperature ?

any leads ?
 
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What's "ppmv"? I have a hunch it comes from "parts per million",bt what does "v" stand for ?

1 mol/cm^3 is the cgs unit for concentration.

Daniel.
 
parts per milion per volume , you just multiply ppm by 1.0e6
 
Are you using ppmv with gasses? A google shows that this appears to be the standard usage.

http://www.ch4.org.uk/glossary.php/Ppmv?term=p

has the usage info,

http://www.rotronic-usa.com/datasheets/Ref/Def/ppm_v.htm

has some sample calculations of how the term is used (with gasses).

If the term is being used for something other than gasses, the approach in the second url probably won't work - but I think it would be a bad idea to use the term for anything other than gasses.
 
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I think i can work with that. Thanx a much
 
I hope u realize you can't make that conversion

dim (mol/cm^3)= S V^{-1}

dim (ppmv)=V^{-1}

Daniel.
 
yeah i had to convert everything into SI units.

ppmv=[(Gas rho) /(air rho) ] * 1.0e6

Gas rho = P/(kT) from P=nkT

thanx very much guys
 

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