1. Limited time only! Sign up for a free 30min personal 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!

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


    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


    User Avatar
    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 )
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook