1. Solutions & Solubility Factors Affecting Solubility

2. What is a Solution? A solution is the same thing as a homogeneous mixture (a mixture with the exact same composition throughout).

3. Parts of a Solution Solute-the substance that is being dissolved in a solution Solvent-the substance in a solution that is being dissolved into.

4. Solution of Two Liquids When two liquids are able to dissolve into each other, they are called miscible. If not, they are called immiscible.

5. What can be dissolved? Remember the saying “like dissolves like” Polar solvents (like water) will only dissolve polar or ionic compounds. *

6. How does solvation occur? IMFs between polar molecule pull ions away from solid. *

7. Solubility Rules The solubility rules will tell you if a compound will be soluble in water. Note, this does not tell us how soluble it is, just whether or not it will dissolve.

9. Soluble or Insoluble? NaNO 3 KClO 4 PbBr 2 K 2 CrO 4 Ca(OH) 2 Fe 2 S 3 AgCl Na 3 PO 4 Hg 2 SO 4 Fe(CN) 3 Ba(C 2 H 3 O 2 ) 2 SrS

10. Precipitation Precipitation is the formation of a solid in a solution during a chemical reaction. The precipitate is the solid formed due to creation of an insoluble compound. The remaining liquid is called the supernatant.

11. Lead (II) nitrate and potassium iodide solutions are mixed together. The yellow stuff is a solid, insoluble compound. What could it be?

12. The positive lead ion could go with the negative iodide ion and the positive potassium ion could go with the negative nitrate ion. Are either of the resulting compounds insoluble?

13. PbI 2 is insoluble, KNO 3 is not, so we say lead (II) iodide precipitates!

14. What precipitate forms between: Barium nitrate and sodium sulfate Potassium chloride and silver acetate Ca(ClO 3 ) 2 and (NH 4 ) 2 CrO 4 KClO 4 and Li 2 Cr 2 O 7 FeCl 3 and Ba(OH) 2

15. Solubility Solubility is the amount of a substance that will dissolve into a quantity of solvent (at a given temperature)

16. Solubility, cont’d A solvent (like water, for example) can only hold so much of a solute.

17. If a solvent cannot hold any more of a solute (at that temperature) it is called saturated. If the solvent can hold more solute, it is called unsaturated.

18. Sometimes, a solution can hold more of a solute than it should theoretically hold. This type of solution is called supersaturated. How could this occur?

19. Factors Affecting Solubility Generally, a substance’s solubility increases as temperature is increased. (This is not true of most gases). Why? The solvent’s particles are moving faster, and so they have more energy to break bonds.

20. In gases, pressure affects solubility. The higher the pressure, the more gas is soluble in a solvent. What is an example of this?

21. Reading Solubility Charts

23. Concentration Concentration-the amount of solute that is dissolved into a solvent Concentrated-when a solution has a high concentration of solute Dilute-when a solution has a low concentration of solute

24. Concentration… Concentration can be described in terms of “weak” or “strong”, “concentrated” or “dilute”, but these are both relative terms and can be subjective.

25. So how do we measure concentration objectively? There are lots of ways!

26. Molarity Molarity is one way to measure concentration; it is the number of moles of solute per liter of solution. Notice, this is volume of the entire solution, not just of the solvent. The unit of molarity is mol/L, which can be abbreviated with an uppercase M.

27. Molarity (M) = When reading a solutions molarity, its numerical value is read as “molar”. So a solution with a molarity of 1.5 would be called a “1.5 molar” solution. moles of solute liters of solution

28. Practice Problem #1 What is the molarity of a solution that contains 0.15mol of MgCl 2 in a 1.13L solution?

29. Practice Problem #2 A saline solution contains 0.020mol of NaCl in exactly 100mL of water. What is the molarity of this solution?

30. Practice Problem #3 How many moles of solute are present in a 1.5L sample of 0.24M Na 2 SO 4 ?

31. Practice Problem #4 A saline solution contains 0.75g of NaCl in exactly 100mL of water. What is the molarity of this solution?

32. Practice Problem #5 What would the molarity of a solution be if you took 1.5L of 0.5M NaOH and added enough water to make the total volume 4.2L?

33. Molality Another way to measure concentration is in terms of molality, which is the number of moles of solute per kilogram (or 1000g) of solvent. The unit of molality is mol/kg, or you can abbreviate with a lowercase m (also usually in italics)

34. Practice Problem #1 What is the molality of a solution made by adding 35.3g of NaCl to 1.34kg of water?

35. Practice Problem #2 What is the molality of a solution made by adding 128.0g MgBr 2 to 895g of water?

36. Practice Problem #3 How many grams of KI must be dissolved in 500.0g of water to make a 0.060m solution?

37. Practice Problem #4 How many grams of CaCl 2 must be dissolved in 350.0g of water to make a 0.905m solution?

38. % Solution You can also talk about solution in terms of a percent of solution. % by volume % by mass % by mass/volume

39. % = part X 100 total

40. Practice Problem #6 What is the percent by volume of ethanol in the final solution when 85mL of ethanol is diluted with water to a total volume of 200mL?

41. Practice Problem #7 What is the percent mass of a solution made by adding 15.5g of sugar to 58.2g of water?

42. Making Dilutions Because only certain molarities are available for purchase, scientists need to be able to dilute a stock solution to get other molarities. To calculate, use: M 1 V 1 =M 2 V 2

43. Practice Problem #1 How many milliliters of 6.0M HCl would you need to make 550mL of 1.5M HCl?

44. Practice Problem #2 What would the molarity of a solution be if you took 1.5L of 0.5M NaOH and added enough water to make the total volume 4.2L?

45. Mole Fraction The final way to measure concentration is with mole fraction, or the ratio of moles of one component to total moles in solution. In any solution, there are two mole fractions, the symbols of which are X A and X B. They do not have a unit.

46. Practice Problem #7 What is the mole fraction of each component in a solution that contains 1.25 moles of ethylene glycol in 4.00 moles of water?

47. Practice Problem #8 What is the mole fraction of each substance in a solution made with 7.8 moles ethanol and 6.2 moles water?