1. Chemistry Chapter 15 Solutions

2. 15.1 Solutions A. Characteristics of Solutions -composed of two parts 1.The substance that is dissolved is the solute 2.The substance that does the dissolving is the solvent 3.A solution may exist as a solid, liquid or gas depending on the state of the solvent. Types of solutions:

3. Solid  Liquid in solid  Example – dental amalgam  Solvent: Silver (solid)  Solute: Mercury (liquid)  Solid in solid  Example – Steel  Solvent: iron  Solute: carbon

4. Gaseous  Gas in gas:  Example - Air  Solvent: Nitrogen  Solute: Oxygen

5. Liquid  Gas in liquid  Example - Soda  Solvent: water (liquid)  Solute: Carbon dioxide (gas)  Liquid in liquid  Example – Vinegar  Solvent: Water  Solute: Acetic acid  Solid in liquid  Example – Ocean Water  Solvent: Water (liquid)  Solute: Sodium Chloride (solid)

6. Aqueous  Any mixture where water is the solvent.

7. 4. Soluble - a substance that dissolves in another substance. 5. Insoluble - a substance that does not dissolve in another substance. 6. Immiscible - two liquids that are insoluble in each other. 7. Miscible - two liquids that are soluble in each other.

8. B. Solvation in Aqueous Solutions 1. If the attractive forces between the solvent and solute particles are greater than the attractive forces holding the solute particles together, the solvent particles pull the solute particle apart and surround them. The solute particles move into solution. This process is called solvation. 2. Solvation of water is called hydration

9. 3. “Like dissolves like” a. aqueous solutions of ionic compounds- The charged ends of the water molecules attract the positive and negative ions making up an ionic solid, forcing them to separate. b. aqueous solutions of molecular compounds- Molecular compounds that have polar sections easily form aqueous solutions with water. B. Solvation in Aqueous Solutions

10. Example of an aqueous solution of an ionic compound forming.

11. C. Solubility 1.Solubility – refers to the maximum amount of solute that will dissolve in a given amount of solvent at specified temperature and pressure. Often expressed in grams of solute per 100g of solvent.

12. C. Solubility 2. Concentration- the amount of solute in a given amount of solvent or solution. Is there a limit to how concentrated a solution can be? Unsaturated solution- a solution in which more solute will dissolve Saturated solution- a solution in which no more solute will dissolve Supersaturated solution- a solution that contains more solute than can normally be dissolved at a given temperature (very unstable, often crystallizes)

13. D. Factors that affect solubility temperature- Generally, as temperature increases, more solid solute will dissolve in the same amount of liquid solvent. The opposite is true for gaseous solutes.

14. 15.2 Solution Concentration A.Expressing concentration: Concentration DescriptionRatio percent by mass percent by volume molarity

15. Expressing concentration:  1. Percent by mass -ratio of the solute’s mass to the solutions mass expressed as a percent.  Example: An aquarium contains 3.6 g NaCl per 100.0 g of water. What is the percent by mass of NaCl in the solution?

16. Expressing concentration:  2. Percent by volume-ratio of the volume of the solute to the volume of the solution expressed as a percent.  Example: What is the percent by volume of ethanol in a solution that contains 35 mL of ethanol dissolved in 115 mL of water?

17. Expressing concentration:  3. Molarity- (M) number of moles of a solute dissolved in a liter of solution  -also known as molar concentration

18.  Example: What is the molarity of a solution that contains 0.65 mol of CuCl2 in 500 mL of water?  Example: What is the molarity of a solution that contains 5.10 g of glucose (C 6 H 12 O 6 ) in 100.5 mL of solution?

19. B. Preparing Molar solutions  1. How is a solution of a known molarity made?  A. Convert moles of solute to grams and measure the amount out.  B. Add solvent so that the total volume of the solution is 1L.  C. For any volume other than 1L we must adjust the amount of solute needed by multiplying it by the fraction of a liter of solution we need.

20. Example  Example: How many grams of CaCl2 would be dissolved in a 1.0 L of a 0.10 M solution of CaCl2?  Example: How many grams of NaOH are in 250 mL of a 3.0 M NaOH solution?

21. 2. Diluting solutions  -because the total number of moles of solute does not change during dilution:  Moles of solute in the stock solution = moles of solute after dilution M1V1= M2V2

22. Example:  What volume, in milliliters, of 2.00 M CaCl2 is needed to make 0.50 L of 0.300 M CaCl2 solution?

23. 15.3 Colligative Properties  Definitions: Colligative means “depending on the collection.”  Depends only on the number of dissolved particles, not the identity of dissolved particles.  Includes vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure

24. Electrolytes and Colligative Properties  electrolyte: Soluble ionic compounds. When they dissolve in solution, they dissociate into their component ions.  Ex: NaCl (aq)  Na + (aq) + Cl - (aq)  covalent molecules in aqueous solution:  Covalent particles do not dissociate wen in solution.

25. 1.Boiling Point Elevation  -Boiling occurs when vapor pressure equals atmospheric pressure.  -Boiling point of a solution is higher than the boiling point of the pure solvent.  -Dissolving substances to increase the boiling point of a solvent. Examples of colligative properties

26. Ex: Antifreeze: a solution of ethylene glycol in water 1. Prevents car’s radiator from freezing in the winter. 2. Prevents car’s radiator from boiling over in the summer The more ethylene glycol in the water, the lower the freezing point, and the higher the boiling point.

27. 3. Freezing Point Elevation  Freezing point of a solution is lower than the freezing point of the pure solvent.  -Dissolving substances to lower the freezing point of a solvent.  Ex: Icy pavement-throw down CaCl2 or NaCl, and the water will then freeze at a lower temperature