1. Not finding help here? Sign up for a free 30min 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!

Thermal Expansion of Gas - am I on the right track?

  1. Oct 13, 2009 #1
    Question:
    One mole of an ideal gas with cv=2.5R, initially at 0.0degC, is heated at constant pressure. How much heat is needed to double its volume?

    Solution:

    Know:
    n=1
    T0=273.15K
    cv=2.5R
    [tex]\Delta[/tex]P=0
    Vf=2V0

    H=U +PV
    and thus, Q= [tex]\Delta[/tex]H
    Q=ncv[tex]\Delta[/tex]T

    We can rearrange to find
    [tex]\Delta[/tex]H=[tex]\Delta[/tex]U +P(2V0-V0) -> since Vf=2V0

    My question is, what do I do with the internal energy? and how can I find the pressure with the given information if I also don't know the final temp?
     
  2. jcsd
  3. Oct 13, 2009 #2

    Mapes

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Hint: it's an ideal gas.
     
  4. Oct 13, 2009 #3
    Well, for an ideal gas PV=nRT.
    And since P is constant, can I say that:

    P0 = (nRT0)/V0
    is the same as
    P= (nRT0)/V0

    so , P= [(273.15K)(nR)]/V0
     
  5. Oct 13, 2009 #4

    Mapes

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    What's the final temperature?
     
  6. Oct 13, 2009 #5
    Honestly, I'm kinda stuck here. It feels to me like with the information I have that I'm just going in circles using one equation to solve another one.
    I don't think this question should even be this confusing...
     
  7. Oct 14, 2009 #6

    Mapes

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Use the ideal gas law to find the final temperature when the volume is doubled at constant pressure.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Thermal Expansion of Gas - am I on the right track?
Loading...