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Homework Help: Thermodynamics chemical reaction problem

  1. Sep 8, 2007 #1
    1. The problem statement, all variables and given/known data
    What are q and w (in kJ) for the reaction of 22 g of Na(s) and 82 g of Cl2(g) to produce NaCl at 1 atm and 298 K.

    2. Relevant equations

    w=-delta(n(g))* R*T where delta(n(g)) = the moles of gas created during the reaction

    3. The attempt at a solution

    First, I wrote the chemical reaction for Na and Cl2

    2Na(s) +Cl2(g)=> 2NaCl

    delta(n(g))=0-1 = -1

    82 g Cl2*(1 mol Cl2/70.98 g Cl2)*(-1 mol gas/1mol Cl2)= -1.16

    delta n(g) =-1.16
    w=-delta(n(g))*RT=(-1.16)(8.314)(298 K)=2.87 kJ

    But thats not the answer according to the back of my textbook.
  2. jcsd
  3. Sep 9, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    The volume is changing from the volume of Cl2 gas to essentially zero.

    Can one apply w = p [itex]\Delta{V}[/itex]? 1 mole of gas has a volume of 22.4 l.

    Then there is the heat.
    Last edited: Sep 9, 2007
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