1. Solutions & Solubility Solubility

2. defined as the maximum grams of solute that will dissolve in 100 g of solvent at a given temperature based on a saturated solution

3. Solubility Supersaturated solutions are not in equilibrium with the solid substance and can quickly release the dissolved solids. Saturated solution is one that is in equilibrium with respect to the dissolved substance. These conditions can quickly change with temperature. SATURATED SOLUTION max amount no more solute dissolves UNSATURATED SOLUTION capable of dissolving more solute SUPERSATURATED SOLUTION over max amount becomes unstable, crystals form Concentration Increasing

4. Solubility Factors Affecting Solubility 1. Stirring (agitation) Increases solubility b/c if fresh solvent is brought in contact with the surface of the solute Surface phenomenon

5. 2. Temperature Increases solubility by increasing kinetic energy, which increases the collisions between molecules of solvent and the surface of the solute Solubility

6. 3. Surface Area A smaller particle size dissolves more rapidly than larger particles size Surface phenomenon More surface area exposed, faster rate of dissolving Solubility

7. Solubility Curve shows the dependence of solubility on temperature Note: the solubility of the gases are greater in cold water than in hot water Out of the solids, which has the lowest solubility at 40°C? KClO 3 Which has the highest? NaNO 3

8. Practice Problems 1. Which of the following compounds dissolved the highest at 20°C? 2. The lowest at 20°C? 3. Overall which compound dissolved the fastest? 4. Name a compound in the graph that is a gas? How do you know it’s a gas?

9. Solubility Solids are more soluble at... Solids are more soluble at... high temperatures. Gases are more soluble at... Gases are more soluble at... low temperatures & high pressures (Henry’s Law). EX: the “bends” & soda When opened partial pressure of CO 2 liquid decreases and the concentration of dissolved CO 2 decreases.

10. Henry’s Law – states that at a given temperature the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) Henry’s Law:S 1 = S 2 P 1 P 2 If the solubility of a gas in water is 0.77 g/L at 3.5 atm of pressure, what is its solubility at 1.0 atm of pressure? (The temperature is held at 25°C) S 1 = 0.77 g/L = X P 1 = 3.5 atm P 2 = 1.0 atm Solubility 0.22 g/L

11. Molarity By definition: the number of moles of solute per liter solution. M = # mol/L Example: Determine the molarity (concentration) of 2 mol of glucose in 5 liters of water. M = 2mol/5L = 0.4M glucose

12. Molarity by Dilution The number of solute particles in a solution does not change when more solvent is added: # moles before = # moles after. Since most solutions are made from concentrated, stock solutions on hand, the molarity of the new solution can be calculated. M 1 V 1 = M 2 V 2 where 1 = stock solution and, 2 = new, dilute solution.

13. Molarity by Dilution cont. Example: How many mL of a stock solution of 2.00M MgSO 4 would be needed to make 100.0mL of 0.400M MgSO 4 ? M 1 V 1 = M 2 V 2 M 1 = 2.00MM 2 = 0.400M V 1 = xV 2 = 100.0 mL

14. Molarity by Dilution cont. 2.00M(xmL) = 0.400M(100.0mL) X = (0.400M x100.0mL)/2.00M X = 20.0 mL of the stock solution

15. Percent Solutions Many products give their concentrations as a percent solution. Percent (mass/volume) is one and the formula is: %(m/v)= (mass solute/mL solution) x 100. Percent (volume/volume) is another. The formula is: %(v/v) = (vol. solute/vol. solution) x 100. Percent (mass/mass) is a third. The formula is : %(m/m) = (mass solute/ mass solution) x 100.