1. Solubility Unit III Lesson 1

2. Unit Intro Our focus is on solutions of aqueous ions As you know; acids, bases and salts form ionic solutions. This unit is only concerned with salts.

3. Review Electrolytes: substances that dissolve to give electrically conducting solutions that contain ions. Ex:

4. Review Non-electrolytes: a substance that dissolves to give non-conducting solutions containing only neutral molecules. Ex:

5. Molecular vs Ionic solutions Ionic solutions metals and non-metals compounds that contain polyatomic ions

6. Molecular compounds They are covalent compounds Non-metal and non-metal especially organic compounds

7. Useful hint When it comes to our chem12 course, you are only going to deal with ionic compounds that have one type of positive ion and one type of negative ion only.

8. Ionic SolutionsMolecular/Covalent Solutions NaCl (aq) C 6 H 12 O 6 (aq) metal or polyatomic ion Ca(OH) 2(aq) C 12 H 22 O 11 (aq) nonmetal or carbon (NH 4 ) 3 PO 4(aq) CH 3 OH (aq) Ca(CH 3 COO) 2(aq) O 2(aq) H 2 SO 4(aq) N 2 H 4 (aq) Conduct electricityDo not conduct electricity

9. Write equations to show the dissolving of the following substances in water NaCl (s)  Na + +Cl - C 6 H 12 O 6 (s)  C 6 H 12 O 6 (aq) Ca(OH) 2(s)  Ca 2+ +2OH - C 12 H 22 O 11 (s)  C 12 H 22 O 11 (aq) (NH 4 ) 3 PO 4(s)  3NH 4 + +PO 4 3- CH 3 OH (l)  CH 3 OH (aq)

10. Back to solubility In chem 11, you learnt that… The solubility of a substance is the maximum amount of the substance which can dissolve in a given amount of solvent at a given temperature.

11. Equilibrium Solubility The solubility of a substance is the equilibrium concentration of the substance in solution at a given temperature. when expressed in moles/L it’s called Molar Solubility.

12. Solubility at equilibirum Solid MgCl 2 dissolves and enters solution dissolving reaction Mg +2 + Cl -1 ions come together to form MgCl 2 crystallization reaction

13. Solubility at equilibrium When the rate of dissolving reaction equals the rate of crystallization reaction, we have equilibrium. –A solution at equilibrium is called a saturated solution.

14. Saturation exists when… Equilibrium exists between the dissolved (ions) and the undissolved material (solid) Some undissolved material is till present (crystal solids)

15. How to saturate a solution & determine solubility To saturate a solution, add weighed portions of your solid to a volume of (solvent) water and stir until full. –A bit of excess solid will always be present at equilibrium saturation though. In order to determine the solubility, you must completely fill or saturate the solution !

16. Mg 2+ Cl - Amount MgCl 2 Dissolved Rate of dissolving > Rate of crystallization Determining The Solubility of MgCl 2 Add measured portions of MgCl 2 to 100.0 mL and stir to dissolve MgCl 2 100.0 mL 10.0 g MgCl 2 10.0 g MgCl 2 10.0 g MgCl 2 3.0 g MgCl 2 0.0 g Rate of dissolving = Rate of crystallization slow very slow 33.0 g equilibrium unsaturated saturated MgCl 2(s)

17. Calculate the solubility in units of g/L and mole/L =3.46 M 0.100 L 95.3g x 1 mole 33.0 g = Molar Solubility = Moles/L Solubility= 33.0 g 0.100 L =330. g/L

18. Equilibrium Equation MgCl 2(s) ⇌ Mg 2+ + 2Cl - Expression:Keq = [Mg 2+ ][Cl - ] 2 do not use the solid The Ksp or (solubility product) is used for saturated solutions at equilibrium Ksp = [Mg 2+ ][Cl - ] 2

19. Un-Saturated, Saturated and Super-satured Review

20. The rate of dissolving > the rate of crystallizing Not at equilibrium Not full – ( more solid can dissolve if you add it) Unsaturated Solutions How does it look? Clear solution!

21. The rate of dissolving = the rate of crystallizing At equilibrium Full- ( adding more solid will not dissolve ) How does it look? it always has crystals/solids in the solution. Saturated Solutions

22. The rate of dissolving < the rate of crystallizing Not at equilibrium Over full – ( adding more solid causes precipitation) How does it look? Clear solution! Supersaturated Solutions Supersaturated video

23. Predicting the solubility of salts Page 332 in your textbook has the table “ Solubility of common compounds in water” Will be provided for you Use it to predict solubility ( high or low ) Use it to predict if a precipitate will form.

24. Ag 2 SO 4 CuSO 4 CuCl 2 CuCl BaS K 2 CO 3 FeSO 4 CaSO 4 Ca(NO 3 ) 2 Na 3 PO 4 High Low High Solubility means >.1 M Low Solubility means .1M High Low High Low High

25. Precipitate Questions Will a precipitate form when 0.2 M solutions of CaS and Na 2 SO 4 are mixed?

26. Write the equation for equilibrium present in a saturated solution of Al 2 (SO 4 ) 3(s) solution. Ksp= [Al 3+ ] 2 [SO 4 2- ] 3 Equilibrium Expression Al 2 (SO 4 ) 3(s) ⇌ 2Al 3+ +3SO 4 2-

27. Write the equation for equilibrium present in a saturated solution of Ca 3 (PO 4 ) 2(s) solution. Ksp= [Ca 2+ ] 3 [PO 4 3- ] 2 Ca 3 (PO 4 ) 2(s) ⇌ 3Ca 2+ +2PO 4 3- Equilibrium Expression

28. pg 74 #1-2, pg 76 #3-7, pg 77 #8-11 Pg 83 #21,22 Pg 84 #24. Practice Time