Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Which of these is spontaneous?

  1. Feb 10, 2005 #1
    Which of these is spontaneous??

    Which of the following are spontaneous at constant T and P ?


    (a) DH = -10 KJ DS = +5 J/K T = 298K

    (b) DH = +5 KJ DS = -5 J/K T = 10K

    (c) DH = -10 KJ DS = -40 J/K T = 300K

    (d) DH = -10 KJ DS = -40 J/K T = 200K

    (e) DH = -10 KJ DS = -40 J/K T = 500K


    DH= enthalpy

    DS= entropy

    all i know about spontaneous reactions is that entropy is greater than zero, and gibbs free energy is negative. Help with this one.
     
  2. jcsd
  3. Feb 10, 2005 #2

    GCT

    User Avatar
    Science Advisor
    Homework Helper

    Solve for delta G, find the equation in your text.
     
  4. Feb 12, 2005 #3

    mrjeffy321

    User Avatar
    Science Advisor

    isnt it choice "A", since that one is giving off energy (exothermic) and it is becomming more dissordered (enthropy is increasing). All the rest are either taking in energy (endothermic) and/or enthropy is decreasing.
    just being exothermic itself isnt enough to be spontaneous but it is a good sign, but when enthropy is increasing that does. or am I wrong.
     
  5. Feb 13, 2005 #4

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    That's not right jeffy, spontanaeity is determined by the free energy, not the enthalpy.
     
  6. Feb 13, 2005 #5

    Gokul43201

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    You've virtually been told everything you need to do. I can't imagine where your difficulty lies.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Which of these is spontaneous?
  1. Spontaneous Reactions (Replies: 2)

  2. Spontaneous ice slush (Replies: 5)

Loading...