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Ksp - background

Na + (aq) + Cl - (aq). NaCl(s). Ksp - background. The equilibrium between solids and ions is different from the equilibrium between gases The equilibrium between solids and ions is a “phase” equilibrium (e.g. NaCl(aq)). Ksp deals with a phase equilibrium: (s)  (aq).

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Ksp - background

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  1. Na+(aq) + Cl-(aq) NaCl(s) Ksp - background The equilibrium between solids and ions is different from the equilibrium between gases The equilibrium between solids and ions is a “phase” equilibrium (e.g. NaCl(aq)) Ksp deals with a phase equilibrium: (s)  (aq)

  2. Solubility and the Solution Process II • Solubility: Amount of solute that dissolves in a solvent to produce a saturated solution. (Solubility often expressed in g/100 mL.) E.g. 0.30 g of I2 dissolved in 1000 g of H2O. • Saturated solution: maximum amount of solute is dissolved in solvent. Trying to dissolve more results in undissolved solute in container. • Unsaturated solution: less than max. amount of solute is dissolved in solvent. E.g. 0.20 g of I2 dissolved in 1000 g of H2O. • Supersaturation = more solute in solution than normally allowed; we call this a supersaturated solution.

  3. Finding the solubility product Ksp First we need an equation To find the equation we need to know the dissolving equation Let’s use the example of CaCl2 The equation would be CaCl2(s) Ca+2(aq) + 2Cl-(aq)

  4. The equation would be CaCl2(s) Ca+2(aq) + 2Cl-(aq) All equilibrium constants have the equation Constant = [Products] [Reactants] And unlike the rate equation equilibrium constants are raised to the power of the coefficient in the balanced equation The equilibrium balance is not effected by how much solid is left Ksp = [Ca+2].[Cl-]2

  5. Finding the solubility product constant Ksp First we need an equation To find the equation we need to know the dissolving equation Let’s use the example of CaCl2 The equation would be CaCl2(s) Ca+2(aq) + 2Cl-(aq)

  6. Step 1 The equation would be CaCl2(s) Ca+2(aq) + 2Cl-(aq)

  7. Step 2 Constant = [Products] [Reactants] The equilibrium balance is not effected by how much solid is left Ksp = [Ca+2].[Cl-]2

  8. Step 3 The equilibrium balance is not effected by how much solid is left Ksp = [Ca+2].[Cl-]

  9. Calculate the solubility product constant for PbCl2, if a saturated solution was found to contain 0.1 M of Pb+2 and 0.2 M of Cl- Step 1 write out ion equation Step 2 write out Ksp equation Don’t forget to raise each ion to the power of it’s coefficient Step 3 substitute in concentrations Step 4 solve

  10. Step 1 write out ion/dissolving equation PbCl2 Pb+2 + 2Cl- Step 2 write out Ksp equation using the steps Ksp = [Pb+2]. [Cl-]2

  11. Calculate the solubility product constant for PbCl2, if a saturated solution was found to contain 0.1 M of Pb+2 and 0.2 M of Cl- Step 3 substitute in concentrations Ksp= [0.1 M][0.2 M ]2 Step 4 solve Ksp= 0.1 M x 0.04 M2 Ksp= 0.004 M3

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