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Homework Help: Chemistry HW PLEASE HELP ME

  1. Nov 6, 2006 #1
    Chemistry HW PLEASE HELP ME!!!!!!!!

    Hello, I have chemistry hw and I have to finish but I'm having a really hard time solving one problem. Anyone, could you please help me?
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    Question. # 24

    H2(g) + 1/2 O2(g) ----- H2O(l) H = -285.8 kJ -----(1)

    N2O5(g) + H2O(l) ----- 2 HNO3(l) H = -76.6 kJ -----(2)

    1/2 N2(g) + 3/2 O2(g) + 1/2 H2(g) ----- HNO3(l) H= -174.1 kJ ----(3)

    calculate the enthalpy change for the fallowing reaction

    2 N2(g) + 5 O2(g) ------ 2 N2O5(g)
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  2. jcsd
  3. Nov 7, 2006 #2
    hmm....for a start, try drawing the born-haber cycle
     
  4. Nov 7, 2006 #3
    Well you have to manipulate those equations so that they cancel out and give you the bottom equation. Then just add up the Delta H.
     
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