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!

Thermodynamics Signs question

  1. Oct 25, 2009 #1
    1. The problem statement, all variables and given/known data
    A gas piston is filled with propane and oxygen at room temperature to a pressure of 1
    atm. The surroundings are 1 atm and room temperature. When triggered with a sparking
    device, the propane reacts with the oxygen to produce lots of heat. Assume the system is
    infinitely flexible (constant pressure is maintained at all times) and that the surroundings
    are infinitely large (the properties of the surroundings never change).
    C3H8(g) + O2(g) >> CO2(g) + H2O(g) + q

    Balanced I believe it becomes... C3H8(g) + 5O2(g) >> 3CO2(g) + 4H2O(g) + q

    I have to fill in a table for two Times. 1. Immediately following reaction, and 2. Long after, in thermodynamic equil. For the variables, dV, dT, dntotal, w, q, and dU.

    We are to assume the rxn takes some measurable amt of time, but does not equil with surroundings until the rxn is complete.

    2. Relevant equations
    w=-PextdV
    dU=q+w
    dT=dV/(nc)

    3. The attempt at a solution
    Since its Isobaric, assuming it will expand, is a closed system, and is exothermic. For Immediately after rxn:
    dV= +
    dT= +
    dn= +
    w= -
    q= -
    dU= -

    For long after the rxn:
    dV= 0
    dT= 0
    dn= 0
    w= 0
    q= 0
    dU= 0

    thanks for anyone's help, it will be greatly appreciated.
     
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?



Similar Discussions: Thermodynamics Signs question
  1. Thermodynamic question (Replies: 0)

Loading...