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Homework Help: Heats of solution + Heat of Reaction ?

  1. Dec 22, 2008 #1
    1. The problem statement, all variables and given/known data

    [tex]FeS_{(s)} + 2HCl_{(aq)} \rightarrow FeCl_{2(aq)} + H_{2}S_{(g)}

    [tex]H^{\circ}_{f}[/tex]values in kilojoules per mole:

    [tex]HCl_{(g)} = -93[/tex]


    [tex]H_{2}S_{(g)} = -20[/tex]

    [tex]FeCl_{2(s)} = -341[/tex]

    [tex]H_{sol}[/tex] values in kilojoules per mole:

    [tex]HCl_{(g)} = -74[/tex]

    [tex]FeCl_{2(s)} = -79[/tex]

    How much heat will be evolved in making 15.2g of [tex]H_{2}S_{(g)}[/tex] at STP from [tex]FeS_{(s)}[/tex] and dilute [tex]HCl_{(aq)} ?[/tex]
    2. Relevant equations
    How do I calculate the heat evolved? I know its pretty useless to calculate the heat of reaction for this entire reaction because i have heats of solution instead. So what can i do ?
  2. jcsd
  3. Dec 22, 2008 #2


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    Staff: Mentor

    Hint: Born-Haber cycle.
  4. Dec 22, 2008 #3
    We arent supposed to learn that
  5. Dec 22, 2008 #4
    So what can i do besides using Borne-Haber process its not even part of the curriculum
  6. Dec 22, 2008 #5


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    Staff: Mentor

    What I was aiming at was that Hess law can be used even when you need to account for things like ionization, dissolution and hydration. Knowing Hf of HCl(g) and Hsol of HCl you can calculate Hf of HCl(aq).
  7. Dec 22, 2008 #6
  8. Dec 22, 2008 #7
    How does knowing Hf of HCl(g) and Hsol of HCl you can calculate Hf of HCl(aq) help me ?
  9. Dec 22, 2008 #8
    Heloooooooooooooooooooooooooooooooooooooo ??????????????????????????????????????
  10. Dec 22, 2008 #9
    I need to convert FeCl2 and HCl into (aq) states right ? to find the enthalpy change of that
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