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Question Re. Ksp

  1. Dec 7, 2008 #1
    1. The problem statement, all variables and given/known data

    For stannous sulfide, SnS, the Ksp = 1.0X10^-25
    For manganese sulfide, MnS, the Ksp = 3.0 x 10^-15

    Assume a solution contains .01 M Sn^2+ and .01 M Mn^2+. If the sulfide ion (S^2-) concentration is increased gradually without any dilution of the first solution, what will be the molar concentration of Sn^(2+) ion when manganese sulfide first starts to precipitate?

    2. Relevant equations

    Ksp = ?

    3. The attempt at a solution

    I've tried this question in what I, and a few of my friends who are stuck on it with me, consider a logical progression. I ended up with [Sn] = 1E-25, [Mn] = 3E-15, =1E-27 and =3E-17, respectively. [Sn][3E-17]=1E-15 and I end up with [Sn]=3.33E-9M. The answer is 3.33E-13 and I don't understand how it was attained. Any help is appreciated, thank you.
  2. jcsd
  3. Dec 8, 2008 #2


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    Staff: Mentor

    0.01x10-17 is not 10-15.
  4. Dec 8, 2008 #3
    Which part of my post are you referring to?
  5. Dec 8, 2008 #4


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    Staff: Mentor

    Anyone. You did the same mistake several times.
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