1. C h a p t e r 11 Solutions and Their Properties

2. Kinds of Solutions01 Kind of SolutionExample Gas in gasAir (O 2, N 2, Ar …) Gas in liquidCarbonated water Gas in solidH 2 in palladium metal Liquid in liquidGasoline (mixture) Liquid in solidDental amalgam (mercury in silver) Solid in liquidSeawater (NaCl) Solid in solidMetal alloys

3. Solute and solvent02 For Gas or solid dissolved in liquid: SOLUTE - dissolved substance SOLVENT - liquid Liquids-liquids (minor component is solute)

4. Will a solution form?03 “LIKE DISSOLVES LIKE”

5. NaCl in water04

6. Free-energy Change05 -∆G  spontaneous  substance dissolves +∆G  nonspontaneous  substance does not dissolve ∆G = ∆H - T ∆S ∆H soln and ∆S soln

7. Entropy of Solution ( ∆S soln ) 06 ∆S soln usually positive

8. Enthalpy of Solution ( ∆H soln ) 07 Solvent - Solvent: Energy is required (+ ∆ H ) to overcome forces between solvent molecules Solute - Solute: Energy is required (+ ∆ H ) to overcome intermolecular forces holding solute particles together Solvent - Solute: Energy is released (- ∆ H) when solute particles are solvated (surrounded by solvent)  greater for small cations  increases with charge

9. Enthalpy of Solution ( ∆H soln ) 08 Exothermic ∆H soln : Favorable process Hot packs - CaCl 2 (s)

10. Enthalpy of Solution ( ∆H soln ) 09 Endothermic ∆H soln : Unfavorable process Cold packs - NH 4 NO 3 (s)

11. Examples11 1. Predict the relative solubilities in the following cases: (a) Br 2 in benzene (C 6 H 6 ) and in water, (b) KCl in carbon tetrachloride and in liquid ammonia, (c) urea (NH 2 ) 2 CO in carbon disulfide and in water. 2. Is iodine (I 2 ) more soluble in water or in carbon disulfide (CS 2 )?

12. Concentration: The amount of solute present in a given amount of solution. 1. Molarity (M) 2. Molality (m) 3. Mole fraction (X) 4. Mass Percent Concentration Units12

13. Concentration Units - important!13 Molarity (M): Molality (m): Mole Fraction (X):

14. Percent by Mass (weight percent): The ratio of the mass of a solute to the mass of a solution, multiplied by 100%.  %bymassofsolute= mass ofsolute mass ofsolution  100% mass ofsolution=mass ofsolute+mass ofsolvent Concentration Units14

15. Concentration Units15 Parts per Million: Parts per million (ppm) = = % mass x 10 4 One ppm gives 1 gram of solute per 1,000,000 g or one mg per kg of solution. For dilute aqueous solutions this is about 1 mg per liter of solution.

16. Example16 A sample of 0.892 g of potassium chloride (KCl) is dissolved in 54.6 g of water. What is the percent by mass of KCl in this solution?

17. Example17 An aqueous solution is 5.50% H 2 SO 4. How many moles of sulfuric acid (MM = 98.08 g/mol) are dissolved in 250.0 g of the solution?

18. Example18 Molality from Mass: Calculate the molality of a sulfuric acid solution containing 24.4 g of sulfuric acid in 198 g of water. The molar mass of sulfuric acid is 98.08 g.

19. Example19 Molality from Molarity: Calculate the molality of a 5.86 M ethanol (C 2 H 5 OH) solution whose density is 0.927 g/ml.

20. Solution Formation20 Solute + solvent  Solution Saturated - equilibrium (equal number of ions going into solution as returning from solution to the crystals) Supersaturated - greater than equilibrium amount of solute

21. Solution Formation21 Solubility: A measure of how much solute will dissolve in a solvent at a specific temperature (saturated solution) Miscible: Two (or more) liquids that are completely soluble in each other in all proportions. Solvation: The process in which an ion or a molecule is surrounded by solvent molecules arranged in a specific manner.