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Homework Help: Ideal Gas

  1. Jan 16, 2014 #1
    1. The problem statement, all variables and given/known data

    The ambient temperature in outer space is about 3.0K. Most of the matter in space is hydrogen gas at a density of about one atom per 3.0m^3. What is the pressure of this dilute gas if it is in thermal equilibrium at the ambient temperature.

    2. Relevant equations

    PV = nRT

    3. The attempt at a solution

    I started with saying that PV = nRT and substituting volume for mass/density since I was given density. I cannot seem to get the correct answer playing with the numbers for mass and density of the hydrogen. The correct answer is 1.4x10-23Pa.
  2. jcsd
  3. Jan 16, 2014 #2
    Show us what you did (in detail), please.
  4. Jan 16, 2014 #3
    Well, like I said, I made the equation

    P = nRT/V

    Then, I replaced volume with mass/density

    P = nRTρ/m

    After that, the units on density are kg/m3, so I converted the mass of hydrogen into kilograms.

    I wasn't given how many moles I had, so I just assumed (probably a bad idea) 1.00mol for simplicity.

    After putting this into my calculator it did not give me the desired answer, but I don't know of any other way to look at the problem unless I am given a number a number of moles.
  5. Jan 16, 2014 #4
    You are given the number of moles in the 3m^3. How many moles is one atom?
  6. Jan 16, 2014 #5

    That makes a lot more sense. I am now getting the correct answer. Thank you very much!
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