1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Minimum work to separate O2 &N2 from air

  1. Jan 9, 2016 #1
    1. assume air is an iseal gas at 25C and 100kPa. the mole fractions of components are nitrogen_0.7567
    oxygen=0.2035 water vapor=0.0303 carbon dioxide=0.0003 Calc. min work to seperate
    a-1kmol O2 at 25C 100kPa
    b-1kmol N2 at 25C 100kPa from atmosphere


    2. Relevant equations
    Wmin=ge-gi=(ho-To.se)-(hi-To.si)



    3. The attempt at a solution
    for ideal gas Wmin=To(si-se)=-R.To. total(Xi.lnxi)
    I assume air is composed of only O2 and N2, min ork is equal to - of the entropy change for mixing process
    but Iam confused it is asked only to seperate 1 kmol O2
     
  2. jcsd
  3. Jan 9, 2016 #2

    Bystander

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    One kmol O2 and one kmol N2.
     
  4. Jan 9, 2016 #3
    1 kmol of oxygen at 25C and 100kPa and
    1 kmol of nitrogenat 25C and 100kPa from atmosphere
     
  5. Jan 9, 2016 #4

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Why do you assume that? It gives the composition, and it includes water vapour and CO2.
    Why does the question confuse you?
    The thing that is not clear to me is how much air you should start with. Perhaps the answer tends to a limit as the initial number of moles tends to infinity.
     
  6. Jan 9, 2016 #5

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Yes, but not from the same air sample. They are presented as two independent questions.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Minimum work to separate O2 &N2 from air
  1. Minimum separation (Replies: 1)

  2. Minimum separation? (Replies: 1)

Loading...