Water mass calculation

1. Jan 22, 2012

xzibition8612

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. Jan 23, 2012

256bits

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 )