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!

Entropy change when converting water to steam

  1. Apr 7, 2013 #1
    1. The problem statement, all variables and given/known data

    At constant atmospheric pressure, 20g of water at 30C is converted into steam at 250C. Assume the heat capacity of liquid water is constant at 4.2 J/gK and the heat of vaporization at 100C is 2260 J/g. The molar heat capacity of water vapor at constant pressure is given by

    [itex]\frac{c_p}{R} = a + bT + CT^2[/itex]

    where [itex] a= 3.634,{ } b= 1.195*10^{-3} K^{-1},{ } c=1.350*10^{-7} K^{-2}[/itex]

    Find the entropy change of the water.

    2. Relevant equations

    [itex]\Delta S = \frac{dQ}{T}[/itex]
    [itex] dQ = \int c_p dT[/itex]

    3. The attempt at a solution
    My first thought was just to plug in the given equation for C_p into (1) and integrating, but I'm not sure how the heat of vaporization comes into play.
     
  2. jcsd
  3. Apr 7, 2013 #2

    BruceW

    User Avatar
    Homework Helper

    There are 3 different 'stages' to this problem. You need to think of what they are, then find the entropy change that happens in each stage.
     
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: Entropy change when converting water to steam
Loading...