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AP Chemistry Test FRQ: Balancing Equations

  1. May 10, 2009 #1
    I have no idea how to do the balanced equations portion of the FR. I know how to balance equations using stoichiometric coefficients, but not the particular type of "balanced equations" on the AP test.

    For example: "a small piece of sodium is placed in distilled water"

    my initial thinking:
    Na + H2O --> NaOH + H+

    but they have as the right answer:
    2Na + 2H2O --> 2Na+ + 2OH- + H2

    Why is my answer wrong? (I have the right species and my answer is balanced...)
    Also, I have no idea when to combine certain species, or keep them separate as ions--do solubility rules account for this?


    Any ideas?
     
  2. jcsd
  3. May 10, 2009 #2
    Nevermind, I asked a friend of mine, and got it resolved... But if anyone has any tips for these unique reaction questions, I would really appreciate it!
     
  4. May 11, 2009 #3

    Borek

    User Avatar

    Staff: Mentor

    You didn't have a orrect species and your reaction was not balanced. H+ is not the same as H2 and not only atoms must be balanced - charge must be balanced too.

    And free hydrogen is diatomic. You were close.
     
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