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Gas stoichiometry questions

  1. Oct 28, 2011 #1
    So iv solved all these problems, id just like someone to take a look at them and see which approach is right.

    The question is in the attachment.

    first approach is i use molar volume for SATP which is 24.76L and multiply 65L with it
    and i get 1609.4L then i use this in the universal gas forumla(i think thats what its called)

    PV=nRT

    (100)(1609.4) = n(8.31)(298)

    (100)(1609.4)/(8.31)(298) = n


    second approach i use is where i just use the 65L of volume as is and put it in the equation, since they both are volumes, which one is the right way?

    PV=nRT

    (100)(65)=n(8.31)(298)
    (100)(65)/(8.31)(298) = n

    which approach is correct?
     

    Attached Files:

  2. jcsd
  3. Oct 28, 2011 #2
    Also another question here, in a 2nd attachment

    v=7.5 L

    t=25C or 298K

    P=100Kpa

    PV=nRT

    (100)(7.5)=n(8.31)(298)

    750/(8.31)(298) =n

    750/2476.38 =nHe

    0.302=nHe (helium)

    mass = n X molar mass

    =(0.302)(4)

    =1.208

    Is this in grams or Kg? the mass of helium?
     

    Attached Files:

  4. Oct 28, 2011 #3

    Borek

    User Avatar

    Staff: Mentor

    No, you don't get 1609L, you get 1609L2 - whatever it means. Watch your units and you will see when your approach doesn't make sense.
     
  5. Oct 28, 2011 #4

    Borek

    User Avatar

    Staff: Mentor

    Again, if you were watching your units answer would be obvious.

    What are units of molar mass?
     
  6. Oct 28, 2011 #5
    g/mol?
     
    Last edited: Oct 28, 2011
  7. Oct 28, 2011 #6
    so the first approach is what will get the correct solution?
     
  8. Oct 29, 2011 #7

    Borek

    User Avatar

    Staff: Mentor

    You havew to guess, you can't check?

    Only if the units make sense. Check if they do. What units should the final answer be in? What units your final answer has?
     
    Last edited: Oct 29, 2011
  9. Oct 29, 2011 #8
    i did check but i wasnt sure, hence the question mark.
     
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