Determining nitrous oxide production

[SoilTech]

I have some field chambers buried in the soil at work here and we collect soil emissions from them at regular intervals. The chambers are designed such that they do not allow a pressure increase, yet they do not freely exchange air with the atmosphere outside the chamber. We've been doing this for many years and using a series of calculations to determine the flux of N2O and therefore greenhouse gas production, nitrogen losses etc. I have the calculations we've been performing to determine the mass of N2O nitrogen lost through the soil emissions, but I am trying to rebuild the calculations from the beginning to satisfy myself that they are being done properly. That being said, here is the problem I will begin with:

I have a gas sample which has been determined to contain 0.363 ppm N2O using a GC equipped with an ECD detector. I want to equate this value to a mass of nitrous oxide contained within my chamber with a volume of 0.0285 cubic meters assuming STP.

Thanks in advance!

 

[Adrmay]

Any help would be greatly appreciated.Answer: The first step is to convert the ppm value of N2O to a mole fraction. To do this, we use the following equation: Mole fraction = (ppm N2O * 10^-6)/(Total moles of gas sample) Assuming that the total moles of gas sample is equal to the number of moles of air in the chamber, we can then calculate the mole fraction of N2O. To calculate the number of moles of air, we use the ideal gas law equation: Number of moles = (Pressure * Volume)/(Gas constant * Temperature) For STP, the pressure is 1 atm, the volume is 0.0285 cubic meters, the gas constant is 0.08206 L atm mol-1 K-1 and the temperature is 273K. Plugging these values into the equation, we get: Number of moles = (1 * 0.0285)/(0.08206 * 273) = 0.001047 moles Now that we have the number of moles, we can calculate the mole fraction of N2O: Mole fraction = (0.363 * 10^-6)/(0.001047) = 3.479 * 10^-5 Finally, we can use this mole fraction to calculate the mass of nitrous oxide in the chamber. To do this, we use the following equation: Mass = (Mole fraction * Number of moles * Molecular weight of N2O) The molecular weight of N2O is 44.013 g/mol. Plugging these values into the equation, we get: Mass = (3.479 * 10^-5 * 0.001047 * 44.013) = 0.001525 g Therefore, the mass of nitrous oxide in the chamber is 0.001525 g.