Ppm, equations, atmosphere/molecules help?

  • Context: Chemistry 
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Discussion Overview

The discussion revolves around a homework problem involving the calculation of gas concentration in parts per million (ppm) based on atmospheric molecule density. Participants explore the conversion of concentration from molecules per cubic meter to ppm and discuss related concepts of percentage concentration.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about calculating the concentration of a gas in ppm from the given atmospheric molecule density.
  • Another participant suggests that the conversion to percentage concentration is similar to ppm, indicating that ppm is derived by multiplying by 10^6 instead of 100.
  • There is a question raised about the reasoning behind multiplying by 10^6 to obtain ppm.
  • Some participants express uncertainty about the definitions and calculations involved in these conversions.
  • A warning is issued regarding posting specific homework questions from The Open University, indicating a concern about academic integrity.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the calculations or the definitions involved, and multiple viewpoints regarding the understanding of ppm and percentage concentration are present.

Contextual Notes

Participants show varying levels of understanding regarding the definitions and calculations for ppm and percentage concentration, and there are unresolved questions about the mathematical steps required for the conversion.

helpemz2011
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Homework Statement




At sea level, there are approximately 2.6 × 1025 molecules m-3 of the atmosphere.
One of the gases making up the atmosphere has a concentration of 3.90 × 1021 molecules m-3. What is the concentration of this gas expressed in parts per million (ppm)?


Homework Equations





The Attempt at a Solution





totally flumoxed once again lol

2.6x1025 - 3.90x1021 = 2.59961x1025

now the answer is wrong, what i have done is wrong and to get the right answer in ppm is completely going over my head for some stupid reason.

Cheers Emma
 
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Can you give answer in %?
 
nope tried even that is escaping me
 
how do i get it into %?
 
39ppm?
 
No.

What is definition of % concentration? ppm is very similar, just instead of multiplying by 100% multiply by 106ppm.

This can be a little bit tricky, as you have to calculate ppm in terms of molecules/molecules, while usually we do it mass/mass or something like that. But other than that it is not different.
 
ok so why multiply by 106?

I just don't get it?

sorry being extra thick today

emz
 
What is definition of % concentration?
 
to be perfectly honest i just have no idea.
 
  • #10
But you do have a book or notes or at least access to internet, and you know how to use google?
 
  • #11
helpmz2011
You may not post any of the TMA questions from The Open University on a public forum. This is considered to be cheating.
 

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