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Homework Help: Mass density of a gas!

  1. Nov 28, 2011 #1
    1. The problem statement, all variables and given/known data
    At 0 degrees, and 1 atm, 0.6 mol of a gas occupies a volume of 0.0134 m^3. what is the mass density? The number density is 2.69x10^25 m-3, the average distance between the gas molecule is 4nm and the total mass is 17.685g.

    2. Relevant equations


    1u=1.66x10^-27 mol-1

    3. The attempt at a solution

    I tried to find N so I did 0.6/6,022x10^23 and got 9.96x10^-25. Then I multiplied this by 2.69x 10^-25 and go 2.68x10^-49 which was wrong.

    I'm not exactly sure how to solve the problem, so any help is appreciated!
  2. jcsd
  3. Nov 28, 2011 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    I'm confused. You have the total mass, and you have the volume it occupies. So, what is stopping you from computing the mass density from that information alone?

    As an aside, the step in red above is wrong. It should be (0.6 mol)*(6.022x1023
    molecules/mol), which you can see gives you a result in "molecules." Always include units in calculations like this in order to catch errors like this.
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