Equilibrium of a Sparingly Soluble Ionic Compound

  • Chemistry
  • Thread starter daphnelee-mh
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  • #1
daphnelee-mh
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Homework Statement:
I can't get the correct answer, isn't it if Ksp>[Mn2+][OH-]^2, there is no precipitation. How to get the specific concentration of [OH-]?
Relevant Equations:
Kb = [NH4+][OH-]/[NH3]
Ksp=[Mn2+][OH-]^2
1572962999036.png

Answer given is 6.61g.
 

Answers and Replies

  • #2
Borek
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You are looking for the highest concentration of OH- that doesn't produce precipitation, don't you?
 
  • #3
daphnelee-mh
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chemistry.jpeg


May I know which step is wrong? thanks
 
  • #4
mjc123
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You have worked out the concentration in g/L. What is the mass in the actual solution?
 
  • #5
daphnelee-mh
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chemistry.jpeg


Is this correct ? thanks.
 
  • #6
mjc123
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It is not quite equal to the given answer; I think that's because you rounded off [OH-] to 1.4e-6 M instead of 1.435e-6 M. Keep the extra digits through the calculation, and round off to the appropriate sig figs at the end.
 

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