Solve Ksp Equation for Sn^2+ When MnS Begins to Precipitate

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Discussion Overview

The discussion revolves around solving the Ksp equation for stannous sulfide (SnS) and manganese sulfide (MnS) in a scenario where the concentration of sulfide ions (S^2-) is gradually increased. Participants are attempting to determine the molar concentration of Sn^2+ when MnS begins to precipitate, focusing on the calculations involved in the Ksp expressions for both compounds.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents the Ksp values for SnS and MnS and outlines their approach to the problem, indicating confusion about the resulting concentration of Sn^2+ when MnS precipitates.
  • The participant calculates the sulfide ion concentration needed for precipitation and derives a concentration of Sn^2+ that they believe is incorrect.
  • Another participant points out a mathematical error in the original calculations, specifically regarding the multiplication of concentrations.
  • A subsequent reply reiterates the same mathematical error, suggesting that it is a common misunderstanding among participants.

Areas of Agreement / Disagreement

There is disagreement regarding the correctness of the calculations presented, with multiple participants identifying errors in the mathematical steps taken. The discussion remains unresolved as to the correct concentration of Sn^2+ when MnS begins to precipitate.

Contextual Notes

Participants have not reached a consensus on the correct approach or solution to the problem, and there are unresolved mathematical steps that contribute to the confusion.

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Homework Statement



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?

Homework Equations



Ksp = ?

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.
 
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0.01x10-17 is not 10-15.
 
Borek said:
0.01x10-17 is not 10-15.

Which part of my post are you referring to?
 
Anyone. You did the same mistake several times.
 

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