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Calculate the Electron Affinity of F(g) in kJ/mole using Hess' Law?

  1. Apr 5, 2014 #1
    1. The problem statement, all variables and given/known data
    Calculate the Electron Affinity of F(g) in kJ/mole using Hess' Law.
    IE1 + IE2 of Sr(g) is 1580 kj
    Hsub of Sr(s) is 144 kJ
    Hdiss of F2 is 79 kJ
    Hf of SrF2 (s) is -1215 kJ
    Hlatt of SrF2 (s) is -2441 kJ


    2. Relevant equations

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    3. The attempt at a solution
    1. Sr(g)+Sr+(g) -> Sr2+(g) + Sr+(g) + 2e-
    2. Sr (s) -> Sr(g)
    3. F2(g) -> 2F(g)
    4. Sr(s) + F2(g) -> SrF2
    5. Sr2+(g) + F-(g) -> SrF2 (s)

    I tried to:

    flip 5
    1/2 * flip 3
    flip 1
    flip 2
    copy 4

    but when I did that, I ended up with an extra 1/2 F2 that I couldn't cancel out. I'm not sure what to do.
     
  2. jcsd
  3. Apr 8, 2014 #2

    DrDu

    User Avatar
    Science Advisor

    In 5. there is a 2 missing before F-
     
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