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Homework Help: Water mass calculation

  1. Jan 22, 2012 #1
    1. The problem statement, all variables and given/known data

    Calculate the mass of water contained in a 0.6 ft^3 vessel under the following conditions:

    a) 15 psia, 300 F

    b) 100 psia, 500 F

    c) 20 psia, 210 F

    d) 60 psia, saturated vapor

    e) 60 psia, saturated liquid

    f) at the critical state



    2. Relevant equations

    PV=mRT

    3. The attempt at a solution

    I suppose the ideal gas equation is valid? Can someone explain to me why or why not?
    Assuming it's valid, for a,b the temperature is above the saturation (boiling) temperature, so R would be the water gas constant? For c, d, e, and f, I don't know what values to plug in for R. Any help would be appreciated. Thanks.
     
  2. jcsd
  3. Jan 23, 2012 #2

    256bits

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    Gold Member

    I think you are to determine if the vessel contains watwr as a vapour, as a liquid, or some combination of both for the cases. Water vapour doesn't follow the ideal as law so I suspect you have to use your steam tables.

    saturation temperature and saturation pressure go hand in hand, so your comment that for a, b the temperature is above saturation temperature is invalid ( the boiling temperature you are thinking of is valid for atmospheric pressure )

    do you know what the terms saturated vapour, saturated liquid and critical state mean - you should familiarize yourself with these terms. ( Use wikepedia if you like, or your textbook should have them defined )
     
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