1. Solutions Homogeneous mixtures containing two or more substances. –Solvent- The substance that dissolves –Solute- The substance being dissolved

2. Solutions May exist as a solid, liquid, or a gas Water is the most prevalent solvent for solutions

3. Solubility Soluble- Can be dissolved Insoluble- Cannot be dissolved Immiscible- When one liquid will not dissolve in another Miscible- When one liquid will dissolve in another liquid

4. Solvation The act of dissolving a solute A solute will dissolve when the attractive forces between the solute and the solvent are greater than the attractive forces holding the molecule together

5. Solvation Water Molecules Na Cl Na Hydration Sphere Cl Hydration Sphere

6. Ionic Solutions As you recall H2O is a polar molecule (charged on each end) An ionic compound is composed of a + and – Ion. These ions are attracted to the oppositely charged end of the water molecule, pulling the ionic compound apart.

7. Ionic Solutions The water surrounds the ions, dissolving the compound.

8. Covalent Molecules Water is also a good solvent for some molecular compounds. Sucrose is a polar molecular compound. Water is also a polar molecule attracts the oppositely charged end of the sugar molecule. This pulls them apart causing solvation by water

9. Factors that Affect the Rate of Solvation Increasing the collisions of solvent and solute increases the solvation rate –Ways to increase collisions Increase the surface area of the solute Increase the temperature of the solution Agitate the mixture

10. Heat of Solution The amount of energy required to form a solution –It takes energy to overcome the attractive forces that hold solute molecules together

11. Solubility The maximum amount of solute that can be dissolved at a given temperature and pressure Expressed in grams of solute per 100g of solvent

12. Types of Solutions Saturated Solution- A solution that contains the maximum amount of solute that it can hold. Unsaturated Solution- A solution that can dissolve more solute Supersaturated Solution- A solution that contains more solute than can normally be held in solution

13. Factors That Effect Solubility Temperature- As temperature increases –solubility increases for solid substances –Solubility decreases for gaseous substances

14. Factors the Effect Solubility Pressure- As pressure increases –Solubility for gases increases

15. Henry’s Law S1 = S2 P1 P2 At a given temperature the solubility of a gas in a liquid is directly proportional to the pressure of a gas above the liquid

16. Practice Problem On Board

17. Concentration A measure of how much solute is dissolved in a specific amount of solvent –Concentrated- Lots of solute per volume –Dilute- Little solute per volume

18. Percent to Describe Concentration Percent by mass Percent by mass= Mass of solute X 100 Mass of Solution

19. Percent by Volume Percent by volume Percent by volume = Volume of Solute x 100 Volume of Solution

20. Molarity Molarity (M) = Moles of solute Liters of Solution Expressed in moles per liter

21. Assignment P. 463 8-10 P. 464 11-13 P. 465 14-16

22. Preparing Molar Solutions How would you make a 1.5 molar solution of sucrose? 1.5 mol X 342g = 513g 1 L 1 mol 1 L

23. Preparing Molar Solutions How would you prepare 100ml of a 1.5 molar solution? 100ml X 1L X 513g = 51.3g 1000 ml 1 L

24. Diluting Solutions M 1 V 1 =M 2 V 2 What volume (in ml) of a 12 M stock solution would be needed to make 50ml of a 2.5 M solution? (12M)(V1) = (2.5M)(.050L) 12V1=.125 V1=.0104L= 10.4ml

25. Molality Molality= moles of solute kg of solvent

26. Mole Fraction X A = n A n A + n B What is the mole fraction of HCl in a solution that contains 21% HCl?

27. Mole Fraction Assume there is 100g of solution This means that 21g of the solution is HCl and that 79g of the solution is water Convert both to moles

28. Mole Fraction 21gHCl 1 mole =.583 moles 36g HCl 79gH2O 1 mole = 4.39 moles 18g H2O

29. Mole Fraction X A = n A n A + n B X HCl =.583 =.117 HCl.583 + 4.39

30. Colligative Properties Properties that depend on the number of particles in the solution but not the identity of the particles –Freezing point depression –Vapor pressure lowering –Boiling point elevation –Osmotic pressure

31. Electrolytes and Nonelectrolytes Electrolytes- Compounds that completely ionize in solution causing it to conduct electricity –Usually ionic compounds Nonelectrolytes- Compounds that do not ionize in solution and do not conduct electricity –Usually molecular compounds

32. Vapor Pressure Lowering When a solute is dissolved in a liquid the vapor pressure is lower above the solution than the vapor pressure of the pure solvent This is due to fewer solvent particles at the interface between the air and the surface of the solvent See diagram on p. 472

33. Boiling Point Elevation The boiling point of a solvent increases as solute is added to the solvent  T b = K b m K b = molal boiling point constant m = molality of the solution  Tb =Value of boiling point elevation

34. Freezing Point Depression As solute is added to a solvent the freezing point is lowered  T f = K f m K f = molal freezing point constant m = molality of the solution  T f =Value of freezing point depression

35. Osmosis and Osmotic Pressure Osmotic pressure increases with increase in amount of solvent Solute increases the number of solvent molecules that move across a membrane increasing the pressure

36. Assignment P. 466 17-20 P. 468 21-23 P. 469 24-25 P. 470 26-30 P. 475 33-39