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Homework Help: Heat of reaction

  1. Mar 2, 2006 #1
    The heat of reaction is:

    My question is: what does the change in pressure do to the energy involved in a reaction?
     
  2. jcsd
  3. Mar 2, 2006 #2

    Hootenanny

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    To increase the pressure you have to do work on the system, thereby increasing the energy. To decrease the pressure (aslong as it is above 1 atm) you have to allow the system to do work. This a bit of a rough and ready explanation I'll admit.
     
  4. Mar 2, 2006 #3
    Ok. Rough but good.
    So, the heat of reaction is the change in the internal energy of the systhem. Right?
     
  5. Mar 3, 2006 #4

    Hootenanny

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    Temperature is the mean kinetic energy of the particles in that system. The average kinetic energy of a system can said to be
    [tex] E_k = \frac{3}{2}kT [/tex]
    The ideal gas law links, pressure volume and temperature:
    [tex]pV = nRT = NkT [/tex]
    [itex]n[/itex] is number of moles; [itex]R[/itex]is molar gas constant; [itex]N[/itex] is number of molecules/particles; [itex]k[/itex] is the Boltzmann constant [itex]= \frac{R}{N_A}[/itex] where [itex]N_A[/itex] is Avagadro's constant.

    For more information on heat see http://hyperphysics.phy-astr.gsu.edu/hbase/heacon.html#heacon . But be aware that this is heat from a physics perspective and chemistry.
     
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