Ksp Equation for CaF2: Coefficients and Stoichiometry Explained

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Discussion Overview

The discussion revolves around the solubility product constant (Ksp) for calcium fluoride (CaF2), focusing on the correct formulation of the Ksp equation and the role of stoichiometry in determining the coefficients and concentrations of the ions involved. The scope includes theoretical and mathematical reasoning related to chemical equilibrium.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Some participants assert that Ksp should be expressed as Ksp=[Ca][F]^2, emphasizing that the coefficients in the balanced equation are used as exponents in the Ksp expression.
  • Others argue that Ksp=[Ca][2F]^2 is a misreading, suggesting that the correct interpretation involves the molar solubility x, leading to Ksp=[x]*[2x]^2.
  • A participant questions the derivation of Ksp=[x]*[2x]^2, indicating confusion over the initial misreading of Ksp=[Ca][2F]^2.
  • Another participant mentions the importance of stoichiometry in determining the concentrations of Ca2+ and F- ions when x moles of CaF2 dissolve.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct formulation of the Ksp equation, with multiple competing views presented regarding the role of coefficients and the interpretation of concentrations.

Contextual Notes

The discussion highlights potential misunderstandings in interpreting stoichiometric coefficients and their application in Ksp calculations, but does not resolve these issues.

staka
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CaF2⇔Ca+2F.
Many places state that Ksp=[Ca][2F]^2; Ksp=[x]*[2x]^2.
I thought the coefficient go into Ksp equation as an exponent. So, Ksp=[Ca][F]^2.

Can anyone explain which is correct, or why [2F]^2 (if that's the correct one)?
 
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staka said:
Many places state that Ksp=[Ca][2F]^2

That's wrong. Are you sure you are not misreading:

Ksp=[x]*[2x]^2.

which is correct - assuming x is molar solubility of CaF2.

Ksp=[Ca][F]^2.

That's correct.
 
Why do we get Ksp=[x]*[2x]^2?
(Ksp=[Ca][2F]^2 is from this.. misread wrong)
 
Simple stoichiometry. If x moles of CaF2 are dissolved - how many moles of Ca2+? How many moles of F-?
 

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