1 Principles of Solubility Chapter 10.2

2 Learning Objectives? What solubility is and how it is determined Recognize various levels of saturation and its relationship to solutions Miscible vs Immiscible Like Dissolves Like Factors that affect solubility Henry’s Law

3 What is solubility? Solubility refers to how much of a solute can be dissolved in solvent Solubility is often expressed in grams of solute per 100 g of solvent (usually data tables are at temp. = 25 o C)

5 When a substance becomes solvated by water, we say it is soluble in water Chemists use the axiom “like dissolves like”:  Polar substances tend to dissolve in polar solvents.  Nonpolar substances tend to dissolve in nonpolar solvents.

A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature. (i.e grams of NaCl dissolved in a 100 g water at 25 o C) An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature. A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature. Types of Solutions An heterogeneous mixture is where you add so much solute to the solvent that it “crashes out”. You can visibly see solute.

9 Miscible vs. Immiscible Two liquids are miscible if they dissolve in each other in all proportions (antifreeze) Two liquids are immiscible if they separate into two phases (oil and water) Liquids that are slightly soluble in each other – partially miscible (ether and H 2 O)

10 What affects solubility? Factors that affect solubility: 1. Polar vs Nonpolar functional groups on a molecule 2. Surface Area of solute 3. Agitation 4. Temperature 5. Pressure (for gases in aqueous solutions)

11 How does temperature affect solubility? Increased kinetic energy causes an increase in particle collisions Solubility of most solids increases with increase in solvent temperature Solubility of gases decreases with an increase in solvent temperature An increase in temperature always shifts the position of an equilibrium to favor an endothermic process

12 How does pressure affect gas solubility? Gas solubility increases as the pressure of the gas increases Henry’s Law: C g = kP g Where C g = concentration of gas in solution and P g = partial pressure of gas over the solution

13 Homework for 10.2 Page 280 #21(a-d), 23(a-d), 27 (a-c)