Example Problem with Complete Solution

2C-1 : Specific Volume of Saturated Mixtures 4 pts
Calculate the specific volume for the following situations:
               
a.) Water at 200oC and 80% quality      
b.) Freon 12 at -60oC and 90% quality    
c.) Ammonia at 500 kPa and 85% quality    
               
Read : This is an exercise designed to drive home the meaning and use of the new concept of the quality of a saturated mixture.  It is crucial to remember that if a quality is given, then the system contains a saturated mixture and you probably need to look up properties of both the saturated liquid and the saturated vapor.
Given : a.) Water : T 200 oC
x 0.80 kg vap/kg tot
b.) R-12 : T -60 oC
x 0.90 kg vap/kg tot
c.) NH3 : P 500 kPa
x 0.85 kg vap/kg tot
Find : V ??? m3/kg for each of the three parts of this problem.
Solution
Part a.) Data from the Saturation Temperature Table of the Steam Tables at 200oC:
Vsat liq 0.001156 m3/kg
Vsat vap 0.1274 m3/kg
P* 1554 kPa
The key equation for this problem is the relationship between the properties of a saturated mixture and the properties of saturated liquid and vapor and the quality.
equation 1 Eqn 1
Now, we can plug numbers into Eqn 1 to answer this part of the question.
V 0.1022 m3/kg
Notice that I kept 4 significan figures in this answer istead of the usual 2 or 3 because there are 4 significant digits in the sat'd liquid and sat'd vapor values.  Perhaps I should have only retained 2 significant digits because there only appear to be 2 significant digits in the quality.  I have assumed that there are more than 2, really 4 or more, digits in the quality.  This may not be a good assumption.
Part b.) Data from the Saturation Temperature Table of the R-12 Tables at -60oC:
Vsat liq 0.000637 m3/kg
Vsat vap 0.63791 m3/kg
P* 22.6 kPa
Now, we can plug numbers into Eqn 1 to answer this part of the question.
V 0.57418 m3/kg
Significant figures are a bit tricky here.
Part c.) Data from the Saturation Pressure Table of the Ammonia Tables at 500 kPa:
Vsat liq 0.00158 m3/kg
Vsat vap 0.25032 m3/kg
Tsat 4.1396 oC
Now, we can plug numbers into Eqn 1 to answer this part of the question.
V 0.21301 m3/kg
Significant figures are a bit tricky here as well.