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Molarity of solution?

Discussion in 'DAT Discussions' started by khadcheemz, Aug 21, 2015.

  1. khadcheemz

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    What is the molarity of a solution of H2SO4 if 100 ml of this solution requires 25 mL of 2 M NaOH for complete neutralization?

    Isn't this N1V1=N2V2?

    I thought it was 1.0 M but its .25 M
     
  2. clutchfans

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    (2mol/L of OH-)(25mL of solution) = 0.5mmol of OH = 0.5mmol of H+
    (0.5mmolH+) (1mmol H2SO4/2mmolH+) = 0.25mmol H2SO4
    0.25mmolH2SO4/100mL = 0.25M of H2SO4 initial.
     
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  3. clutchfans

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    You can do it this way because NaOH is a strong base, so you can assume it dissociates 100%.
    H2SO4 is a strong acid you have to assume the it also dissociates 100% twice.
     
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  4. 510586

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    You still do 2 N but I'm not sure if it dissociates 100% the second time.
     
  5. clutchfans

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    Yeah, in the real world you know the second H doesn't dissociate 100% but i guess in terms of the DAT you would have to assume it does.
     
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  6. 510586

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    Oh ok just checking thanks. On a pH problem they could potentially ask it like that right? Then we would treat the second H as not a complete [H+] right?
     
  7. clutchfans

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    That's a really good question. I think if its a strong acid, you can assume this. If it isn't a strong acid you can't assume this.
    If you have a specific question, I think it would be best to ask Dr. Romano.
    Also, if they don't give you any pKa's or Ka's, your going to have to assume it dissociates twice.
     
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  8. clutchfans

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    If you have DAT destroyer, I'm sure there are a few questions like this.
     
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  9. 510586

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    I do, but I don't recall a question involving the pH of a diprotic other than like Ba(OH)2. But I think they treated it as a total OH. Should be the same type of approach though right?
     
  10. clutchfans

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    I would think so, but I'm not 100 percent sure.
     
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  11. OP
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    khadcheemz

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    Wow that was simple! Thanks guys!
     
  12. clutchfans

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  13. gooperwooper

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    chad says that H2SO4 only fully dissociates once just fyi
     
  14. 510586

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    The N would still be 2 though right?
     

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