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Homework Help: Question about Ideal gas law and its application

  1. Mar 22, 2015 #1
    1. The problem statement, all variables and given/known data
    Estimate partial pressure of nitrogen in atm in a room where you are at this moment. Use an ideal gas approximation and assume that air is composed of only nitrogen and oxygen. Show how you arrive the final answer in detail.
    2. Relevant equations
    pv=RT, while p stands for pressure, v stands for specific volume([itex]m^3/kg[/itex]), T stands for temperature(K) and R stands for gas constant(kJ/Kg*K). R for Air is 0.2870, Nitrogen it is 0.2968, and for oxygen it's 0.2598.

    3. The attempt at a solution

    First of all, by volume, air is 80% nitrogen and 20% oxygen. This information is considered essential to find out what is the partial temperature of nitrogen is.
    My room's temperature is 21 degrees celcius, so Kelvin temperature is about 294.15K. So, in the equation pv=RT, RT = 0.2870*294.15 = 84.42105. I wanted to find out what is specific volume of air as ideal gas so that I can find out what the pressure is, but I wasn't able to. I made several attempts, but I wasn't able to go further.
  2. jcsd
  3. Mar 22, 2015 #2

    Quantum Defect

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    Homework Helper
    Gold Member

    There are many points above which indicate that you are confused about many things.

    (1) Ideal gas law -- assumes that all gases show the same ideal behavior. Equation of state : PV = nRT (R = 8.314 J/K-mole) -- assumes P, V are in SI (Pa, m^3) R is independent of gas.

    (2) Partial pressures are useful in discussing amounts (moles) of gas: If, V, T are constant, then P ∝ n. If air is 80% Nitrogen, then p_N2 = 0.80 P_total. You need to know what the total pressure of the room you are in. You can google the weather to see what the barometric pressure is in your area, and take 80% of that (or use a number for composition with better precision) to determine the partial pressure of N2.
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