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!

Misunderstood Thermodynamic question

  1. Mar 31, 2012 #1
    1. The problem statement, all variables and given/known data
    Plot cp as a function of temperature for O2? How does this compare with the cp expected for a diatomic ideal
    gas. Add this constant value to your plot. At what temperatures does the real value of cp approach that
    expected for a diatomic ideal gas.


    2. Relevant equations

    I plot the Cp as a function of temperature for O2?

    the second part totally i misunderstand it i don't know what i should do

    3. The attempt at a solution

    this is what i did ( see that attachment please)

    if u want to see the tables (click here )

    table number 2.
     

    Attached Files:

  2. jcsd
  3. Apr 1, 2012 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Looks to me like you plotted cp for oxygen vs. hydrogen. You were asked to plot cp for oxygen vs. cp for an ideal diatomic gas, which the problem states is a constant.

    What is cp for an ideal diatomic gas?
     
  4. Apr 1, 2012 #3
    I have just the general formula of diatomic !
     
  5. Apr 1, 2012 #4

    rude man

    User Avatar
    Homework Helper
    Gold Member

    So graph it already!
     
  6. Apr 1, 2012 #5
    Sorry I'm really bad in this :(
    This is the general formula
    cp = 7/2 R

    What is the values of R that I have to put it.
    Im thinking to calculate the Cp by taking the R value of O2 from table. But I will get only one point how I would graph it
     
  7. Apr 1, 2012 #6

    rude man

    User Avatar
    Homework Helper
    Gold Member

    If I give you y = y(x) and say y = cosntant, you know how to graph it, don't you?
     
  8. Apr 1, 2012 #7
    the value of R at 300 is 0.2 something
    so i calculate it and plot it to the graph and that what i got
     
    Last edited: Apr 1, 2012
  9. Apr 1, 2012 #8

    rude man

    User Avatar
    Homework Helper
    Gold Member

    What happened to cp = 7R/2 where R is the theoretical, constant value of R?
     
  10. Apr 1, 2012 #9
    i changed my answer. the R is constant at 300 K so i put the point at 300 K
    is it now correct ?
     

    Attached Files:

  11. Apr 1, 2012 #10

    rude man

    User Avatar
    Homework Helper
    Gold Member

    The theoretical R is the same for all gases and is temperature-independent. But be aware that your units of R must be compatible with the units of your chart (the varying values of cp for O2.

    Also, when you do get the right value for R, since it's temperature-independent, what is the correct way to graph it on your graph?
     
  12. Apr 3, 2012 #11
    Oooooh I got it thank you very much :D I made the straight line cuz its constant
     
  13. Apr 3, 2012 #12

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Ats'a way to go!
    What's your total graph look like anyway?
     
  14. Apr 3, 2012 #13
    I'm using my iPad so I can't upload it. I'll upload it once I get home. Thank you toooooo much
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Misunderstood Thermodynamic question
Loading...