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Entry Task: March 1 st Friday

Entry Task: March 1 st Friday . Question: The solubility product of a sparingly soluble salt AX 2 is 3.2 x 10 -11. Provide its solubility in mols /Liter You have 5 minutes!. I can…. Explain the factors that can affect the Ksp of a substance

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Entry Task: March 1 st Friday

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  1. Entry Task: March 1st Friday Question: The solubility product of a sparingly soluble salt AX2 is 3.2 x 10-11.Provide its solubility in mols/Liter You have 5 minutes!

  2. I can… • Explain the factors that can affect the Ksp of a substance • Calculate the changes that occurs when these factors are applied to a solution

  3. Chapter 17Additional Aspects of Aqueous EquilibriaSection 5

  4. CaF2(s) Ca2+(aq) + 2F21-(aq) 17.5- Factors that affect solubilityCommon-ion effect Describe how the common-ion effect affects solubility. When we add either Ca+2 or F- ions, it shifts the equilibrium to the left – reducing the solubility.

  5. Mg(OH)2(s)  Mg2+(aq)+ 2OH1-(aq) 17.5- Factors that affect solubilitySolubility and pH Provide the equation and Ksp for Magnesium hydroxide. 1.8 x 10-11

  6. Mg(OH)2(s)  Mg2+(aq)+ 2OH1-(aq) 17.5- Factors that affect solubilitySolubility and pH 1.8 x 10-11 10.52 What is its pH after the solution is saturated?______ What is the [Mg+2]?__________________ Suppose you add an saturated solution of Mg(OH)2 that is buffered at a more acidic with a pH of 9.0. What is the pOH?_____ What is the [OH-]?_________________ NOW substitute the [OH-] value into the Ksp expression. 1.7 x 10-4 M 5.0 1.0 x 10-5 M 1.8 x 10-11 = [x] [1.0 x 10-5]2 Mg+2= 0.18M

  7. Mg(OH)2(s)  Mg2+(aq)+ 2OH1-(aq) 17.5- Factors that affect solubilitySolubility and pH 1.8 x 10-11 NOW substitute the [OH-] value into the Ksp expression. Solve for the Mg+2 concentration: What is the [Mg+2] concentration before in comparison after the buffered solution was added? 1.8 x 10-11 = [x] [1.0 x 10-5]2 Mg+2 = 0.18M Before 1.7 x 10-4 M after Mg+2 = 0.18M The solubility increased dramatically!

  8. Mg(OH)2(s)  Mg2+(aq)+ 2OH1-(aq) 17.5- Factors that affect solubilitySolubility and pH 1.8 x 10-11 What is the [Mg+2] concentration before in comparison after the buffered solution was added? What would happen if we kept decreasing the concentration of [OH-] ions? Before 1.7 x 10-4 M after Mg+2 = 0.18M Adding acid will decrease the OH- ions and therefore increase the solubility of Magnesium hydroxide

  9. CaF2(s)  Ca2+(aq)+ 2F1-(aq) 17.5- Factors that affect solubilitySolubility and pH What happens to the solubility of CaF2 when a weak acid like HF is added? What is the general rule about salts of basic ions? Like the Mg(OH)2 the solubility of CaF2 will increase. The solubility of slightly soluble salts containing basic anions increases as [H+] increases (lowering pH).

  10. Factors Affecting Solubility • pH • If a substance has a basic anion, it is more soluble in an acidic solution. • Substances with acidic cations are more soluble in basic solutions.

  11. 17.5- Factors that affect solubilityFormation of Complex ions Lewis acids are electron-pair acceptors towards water molecules. What are Lewis acids? What are Lewis bases? The water molecules act as Lewis base which are electron-pair donors

  12. AgCl(s)  Ag1+(aq)+ Cl1-(aq) 17.5- Factors that affect solubilityFormation of Complex ions How does ammonia (NH3) drive the equilibrium? What does this say about the interaction between NH3 and the metal salt with water? By adding NH3, increases the solubility of AgCl moving the equilibrium to the product side The NH3 increases the solubility of the metal salt, it must be able to interact more strongly with the metal ion that with water does.

  13. AgCl(s)  Ag1+(aq)+ Cl1-(aq) 17.5- Factors that affect solubilityFormation of Complex ions Complex ion What is this interaction called?_____________________ What is the relationship between the Kf and stability? What is the general rule about solubility of metal salts? The stability of the complex ion can be judged by the size of the equilibrium constant for its formation (Kf) from the hydrated metal ion. The solubility of a soluble metal salts increases in the presences of a suitable Lewis base.

  14. Factors Affecting Solubility • Complex Ions • Metal ions can act as Lewis acids and form complex ions with Lewis bases in the solvent.

  15. Factors Affecting Solubility • Complex Ions • The formation of these complex ions increases the solubility of these salts.

  16. 17.5- Factors that affect solubilityAmphoterism Substances that are soluble in strong acids and bases because they themselves are capable of behaving as either an acid or base. What is an amphoteric substance? Acids promote the dissolving of… Compounds containing basic anions

  17. 17.5- Factors that affect solubilityAmphoterism What is special about amphoteric oxides and hydroxides… How does the presence of amphoteric substances affect the solubility? They can also dissolve in strongly basic solution. Because they can go both ways (acid/base) it increases the solubility of the compound.

  18. 17.5- Factors that affect solubilityAmphoterism Weak acid Follow the sequence of Al(H2O)6+3, this complex compound acts as a ___________ in water. What happens when a strong base is added? It loses protons (H+) until it becomes neutalized.

  19. Factors Affecting Solubility • Amphoterism • Amphoteric metal oxides and hydroxides are soluble in strong acid or base, because they can act either as acids or bases. • Examples of such cations are Al3+, Zn2+, and Sn2+.

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