Calculate Mass of NO2 in a Liter of Air

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In summary, the mass of NO2 in a liter of air at 6:00 am, with a concentration of 0.920 ppm and 2.46x10^22 molecules of air, is approximately 2 micrograms. This is calculated using the molar mass of NO2 and the ideal gas law.
  • #1
physicsman2
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Homework Statement


NO2 is a known air-pollutant resulting from the combustion of petroleum in vehicles. Suppose at 6:00 am, there are 0.920 ppm NO2 in a liter of air. Calculate the mass (in grams) of the NO2 present in a liter, assuming there are 2.46x10^22 molecules of air in 1.00 L. (1 ppm = 10-6)

Homework Equations


particle to mole to mass conversion
PV=nRT(maybe)

The Attempt at a Solution


I have no idea how to do this. The only thing I could think of is changing the number of molecules to some mass by changing it to moles than use the molar mass of NO2 to get mass
I would appreciate any help on this. Thanks.
 
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  • #2
You are given the number of molecules in a liter of air
You know that 920/1000000 of these are NO2

Do you know the mass of NO2 in AMU?
Do you know the mass of a single AMU in grams
 
  • #3
i know the molar mass of NO2 is 46g/mol. I don't think you need amu, unless the molar mass is the amu. Would I need to use the ideal gas law?
 
  • #4
physicsman2 said:
i know the molar mass of NO2 is 46g/mol. I don't think you need amu, unless the molar mass is the amu.
The molar mass is the mass in grams of 1mole of molecules. An amu is 1g/1mole.
So you work out how many moles there are and multiply by 46h

Would I need to use the ideal gas law?
No
 
  • #5
ok, so after dividing 2.46x10^22 by 6.022x10^23 and multiplying by 46, i get 1.87g. What do I have to do after this, I'm kinda confused. I know the answer should be 1.73x10^-6 but I don't know how to get it.
Thanks a lot.
 
  • #6
There are 2.46x10^22 molecules in 1 litre of air
0.920ppm is NO2 so 0.92e-6 of these are NO2

So we have 2.46x10^22 * 0.92x10^-6 = 2.26x10^16 molecules of NO2 / litre
You know 6.02x10^23 molecues of NO2 weigh 46g

So how much does 2.26x10^16 molecules weigh?
 
  • #7
ps with numbers like this it's always worth doing an estimate first.
We know that 1mol of a gas is 24litres at room temp/pressure
So 24litres would be 46g, then 1 litre NO2 is about 2g.

But we know that NO2 is only 1ppm - so the answer should be around 2 micro grams
 
  • #8
thanks a lot. i see how that answer was found now.
 

Related to Calculate Mass of NO2 in a Liter of Air

What is the formula for calculating the mass of NO2 in a liter of air?

The formula for calculating the mass of NO2 in a liter of air is: Mass of NO2 = (Concentration of NO2 in parts per million) x (Molecular weight of NO2) x (Volume of air in liters).

How do I determine the concentration of NO2 in parts per million?

The concentration of NO2 in parts per million can be determined by dividing the volume of NO2 (in milliliters) by the volume of air (in liters) and multiplying by 1 million.

What is the molecular weight of NO2?

The molecular weight of NO2 is 46 grams per mole.

What is the volume of air in liters?

The volume of air in liters can vary depending on the specific conditions and location. However, for most calculations, a standard volume of 1 liter is used.

Can I use this calculation for other gases in the air?

This calculation is specifically for determining the mass of NO2 in a liter of air. To calculate the mass of other gases, you would need to use a different formula and the molecular weight of the specific gas you are interested in.

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