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Acid equilibria with delta G

  1. May 12, 2014 #1
    Hello Forum!
    I have this review package for my final full of weird mistakes. Problem is that it is hard for me to know if the solutions are right or not:
    Could you please look at this problem I attached?

    They bizarrely switch from HA to HB. Is that just a typo?

    Then, the sign of DG° seems to be wrong! We are looking at the forward reaction, ie it is positive!

    I have my final very soon. Any help is appreciated!
     

    Attached Files:

  2. jcsd
  3. May 12, 2014 #2

    Qube

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    Where is HA? I do not see it in your attached picture.
     
  4. May 12, 2014 #3
    I attached two pictures, one is really tiny. Sorry about that.
     
  5. May 12, 2014 #4

    Qube

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    The HA is a typo. The work backs it up. Your teacher means HB.
     
  6. May 12, 2014 #5

    Qube

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    Also what do you think the sign on delta G standard should be and why?
     
  7. May 12, 2014 #6
    It looks like a typo in the problem statement.

    Chet
     
  8. May 12, 2014 #7
    Hmm.. I may have been mistaken. Tell me if I make sense:
    So we use Ka (dissociation of HA). Plug that into -RTln(Q)=DG°.
    Now, I must reverse the sign because I'm looking at the REVERSE process.
    In the end, I get a negative result, which confirms my teacher's answer!
     
  9. May 12, 2014 #8

    Qube

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    I would say that because your teacher uses double headed arrows, he's referring to an equilibrium, and therefore delta G should be 0. But this isn't relevant because your teacher refers to delta G standard.
     
    Last edited: May 12, 2014
  10. May 12, 2014 #9
    This is not correct. ΔG should be zero, not ΔG standard.

    Chet
     
  11. May 12, 2014 #10

    Qube

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    Good point! I'll fix it.
     
  12. May 12, 2014 #11
    So, was my final response right6?
     
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