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Scientific advice needed, gas and temperatures.
Snowflake
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Hey everyone, I'm finishing up a gas system I've been programming but one problem I've had deals with units. I don't know much about gases really. Right now I'm not using any real world units to quantify the amount of a gas in the air. So for example, you might analyze a sample of air, and find that it has 14 Oxygen and 50 Nitrogen, which means the total air has 64 gas units and is about 21% Oxygen and 79% Nitrogen. The question is, how do I convert these individual values, 14 and 50 into something somewhat realistic, and what should the unit of measure be? Psi? Kpa? Moles?
Further more, if I wanted to calculate the actual total pressure of the air here, would it be as simple as adding up the values for each gas present in the air sample and converting it to another unit or do I have to keep track of the size of the gas molecules, multiply them by the quantity of the gas in the air sample and then add up these results for all gases?
Also, how would temperature affect the final pressure? Is the pressure higher in a room with hotter air than a cold room with the same amount of air?
Further more, if I wanted to calculate the actual total pressure of the air here, would it be as simple as adding up the values for each gas present in the air sample and converting it to another unit or do I have to keep track of the size of the gas molecules, multiply them by the quantity of the gas in the air sample and then add up these results for all gases?
Also, how would temperature affect the final pressure? Is the pressure higher in a room with hotter air than a cold room with the same amount of air?
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when we want to fiddle with it. Now this is an approximation since we pretend we are dealing with an ideal gas which we really aren't but it is a pretty good approximation which gets the job done at low densities and high temperatures. If we wanted more accurate output especially if we were working at higher densities we would probably be using van der Waals equation since that contains correction terms.
Dalton's law of partial pressure gives the total pressure when we have several gases and it is pretty much that you need to add the various pressures to form the total pressure. Though if you are just looking for the total pressure you can just add the numbers of moles and use the ideal gas law directly.
When it comes to thermodynamics the problem is usually that we are stuck with only being able to measure the macroscopic terms like pressure, temperature and volume so when we want the microscopic terms such as the number of particles our best bet tends to be using things like the ideal gas law and other discovered relationships. So if you have p, T and V you can calculate the number of moles in a given and suddenly you have a nice constant to use if you want to fiddle with the values for p, T or V.
Using the ideal gas law we can get an overview of what would happen if we increased the temperature. It would mean that either the pressure increased, which would happen if say our substance was trapped in a container that didn't allow expansion, or if the container allowed it we would be seeing a volume expansion.
I suggest using either kPa or Atmospheres for your pressure, and remember, 1 Atm = 101.3 KPA.
Well, an ideal gas. Not a real gas. Though as has been pointed out, air behaves not too far off from ideal at STP.