1. Solubility and Why Things Dissolve

2. Solutions A homogeneous mixture solute - dissolves (usually smaller amount) solvent – causes solute to dissolve(usually larger amount)

3. Types of solutes Electrolytes ▫ Ionic compounds are hydrated ▫ Electrolytes conduct electricity in aqueous solutions Nonelectrolytes ▫ Molecular solutions ▫ Non-conductive

4. Types of Solutions Solid solution (solid solvent) Gaseous solution (gas solvent) Liquid solution (liquid solvent) Aqueous Solution (water solvent)

5. Solubility – does it dissolve? Soluble ▫ Strong electrolyte ▫ Strong Acids and Bases Insoluble (misleading) ▫ Always some solubility  Is lead soluble in water  Why don’t we use lead pipes ▫ Weak electrolyte ▫ Weak acids and bases

6. How much dissolves? Saturation Unsaturated Less than the maximum amount of solute dissolved Saturated Maximum amount of solute dissolved(extra precipitates out) Supersaturated More than the maximum amount of solute dissolved

7. Solubility Curve Measure how much solute will dissolve in 100. g of water (solvent) at a particular temperature g solute vs temperature 100. H 2 O

8. Solubility Curve - Solids The solubility of solids increases with temperature Saturated online Unsaturated underline Supersaturated Overline

9. Solubility Curve- Gases The solubility of gases decreases with temperature

10. Water’s Unique Properties Universal solvent Solid less dense than liquid High boiling point High surface tension

11. Why does water have these properties? Water is a polar molecule Water is a polar molecule Water can form a Hydrogen Bond Water can form a Hydrogen Bond

12. Polar Molecule A molecule with a + A molecule with a + and a – end and a – end H is + H is + O is – O is –

13. Hydrogen bond + H atoms of one molecule are attracted to + H atoms of one molecule are attracted to - O atoms of another molecule - O atoms of another molecule

14. Why does it dissolve? “ Like dissolves like” Polar dissolves polar ▫ Different ends Non-polar dissolves non-polar ▫ Same ends Will this dissolve? CO 2 in H 2 OKBr in H 2 O CO 2 in CH 4 KBr in CH 4

15. Solvation Dissociation – decomposition of a ionic compound into hydrated ions Hydrated – charged ions surrounded by water molecules Solvation – processing of dissolving

16. Dissolving Salt Crystal

17. Lab: Solubility

18. Solution concentration The amount of solute dissolved in a specific amount of solution 1. Written as a % (for large amounts) g solute x 100% g solution 2. Molarity (M)Moles solute L solution 3.Molality (m)moles solute Kg solvent

19. Colligative Properties Properties that depend on the amount of solute added to solution Boiling point elevation Freezing point depression

20. T = K f x m x i Change in temperature K f = freezing point constant Molality i= number of particles in solution

21. Problems Calculate the percent of a solution that is made of 14.6 g NaCl in 123 g water. If a solution is 67.3 % KI, how many g of KI are added to 376 g solution?

22. Problems Calculate the molarity of a solution with 30.0 g NaCl with water added to make 250 mL solution Calculate the molarity of a solution with 45.7 g KCl to make 500 mL solution

23. More Calculate the g to make 600. mL of a.35 M NaCl. Calculate the g to make 550 mL of a.36 M KOH

24. Making solutions Show calculations to make 100 mL of.10 M using NaOH Then go back and make it and label the flask for future use

25. Dilution If you have a solution and want it at a lower Molarity M 1 x V 1 = M 2 x V 2

26. Problems How would you dilute a 2.5 M stock solution of H 2 SO 4 to make 200 mL of.15 M H 2 SO 4 ?

27. Making your dilution Show calculation for maing 100 mL of.1 M HCl from a 2.5 M stock solution Then go back and make it and label the flask for future use.

28. Molarity Moles per liter M = mol / liter Liters x Molarity = moles L x mol = mol L Moles / Molarity = liters Mol x 1 = L mol / L

29. Calculate molarity, molality Molarity Moles per liter Moles Solute Liters of solution Molality Mole per kilogram Moles solute Kilograms solvent

30. Solubility (g solute/100g H 2 O)

31. Notice at 90 C there is more solute than solvent! This solid has a lower solubility In hot water than cold There is almost no difference In cold and hot solubility Temperature ºC

32. Gases Solubility (g solute/100g H 2 O) Warmer temperature means Less DO (dissolved oxygen) Poor fishies

33. Solubility (g solute/100g H2O) How much KNO 3 will dissolve in 100.0 g of water at 80.0 C? How much KNO 3 will precipitate when a saturated solution at 80.0 C is cooled to 20.0C?

34. How much sugar will dissolve in 50.0 g of water at 60.0 C? Solubility (g solute/100g H 2 O) How much sugar will precipitate if 760 g of a saturated solution at 60 C is cooled to 20 C. 140. g 160. g