Concentration of nitrogen oxide in air

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Discussion Overview

The discussion revolves around calculating the concentration of nitrogen monoxide (NO) in air, given the equilibrium reaction with nitrogen dioxide (NO2) and the total concentration of both nitrogen oxides. The context includes a specific scenario involving air composition, temperature, and pressure, and it is framed as a homework problem.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant expresses uncertainty about the definition of parts per million (ppm) in this context, questioning whether it refers to moles over total moles.
  • Another participant suggests looking for an equilibrium constant at the given temperature and pressure to relate the moles of NO2 to NO.
  • A third participant recommends posting the question in the chemistry section of the forum for more targeted assistance.
  • A repeated post reiterates the original problem statement and expresses similar uncertainties regarding the calculation of NO2 concentration at equilibrium and the definition of ppm as mole fraction times one million.

Areas of Agreement / Disagreement

Participants generally express uncertainty about the approach to the problem and the definitions involved, with no consensus reached on how to proceed with the calculations.

Contextual Notes

There is a lack of clarity regarding the equilibrium constant and how to apply it to find the concentrations of NO and NO2. The definition of ppm as it relates to this specific problem is also not universally agreed upon.

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Homework Statement



The relative compositions of the pollutants NO and NO2 in air are governed by the reaction

NO + 1/2 O2 ⇔NO2

For air containing 21-mol% O2 at 25C and 1.0133 bar, what is the concentration of NO in parts per million if the total concentration of both nitrogen oxides is 5 ppm? Note ppm is taken on a molar basis for gases.


Homework Equations





The Attempt at a Solution



For this problem I am not sure how to go about it. I am not 100% sure if ppm means moles/total moles. Also, I am not able to find out the concentration of NO2 at equilibrium, which is why I haven't been able to get the concentration of NO.
 

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My chem study is too long ago to be able to help you. But I think I'd be looking for some sort of equilibrium constant at that temp & pressure, to be able to relate the proportion of moles of NO2 to NO. Do you have that?

Have you tried a google search? Often you can find a worked example on which you can base your approach.
 
Pose this in the chemistry section of PF.
 
Woopydalan said:

Homework Statement



The relative compositions of the pollutants NO and NO2 in air are governed by the reaction

NO + 1/2 O2 ⇔NO2

For air containing 21-mol% O2 at 25C and 1.0133 bar, what is the concentration of NO in parts per million if the total concentration of both nitrogen oxides is 5 ppm? Note ppm is taken on a molar basis for gases.


Homework Equations

.



The Attempt at a Solution



For this problem I am not sure how to go about it. I am not 100% sure if ppm means moles/total moles. Also, I am not able to find out the concentration of NO2 at equilibrium, which is why I haven't been able to get the concentration of NO.
In this context, ppm means mole fraction times 1 million.
 

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