1. Chapter 13 Water and Its Solutions Section 13.2 Solutions and Their Properties

2.  Submicroscopic interactions between water and solutes determines how much solute it dissolves  Ionic substances are soluble in water  Electrical conductivity is observed when ionic compounds are dissolved in water Ex: Salt Solubility

3.  The process by which charged particles in an ionic solid separate from one another  Water molecules are polar- have a positive and negative end  Water molecules are attracted to ionic compounds that have dissociated into both positive and negative charged ions Examples: H 2 0 NaCl(s) → Na + (aq) + Cl - (aq) H 2 0 SrCl 2 (s) → Sr + (aq) + 2Cl - (aq) DISSOCIATION (ionic compounds)

5. Water is also good at dissolving covalent compounds Ex: Sucrose (table sugar) The molecules are simply separated by water molecules, No dissociation occurs Water dissolves both ionic and covalent substances, however, it does NOT dissolve everything Covalent Compounds

6. Dissolving occurs when similarities exist between the solvent and the solute Examples:  Water can dissolve salt because water is polar and it tends to dissolve ionic substances  Water can dissolve sugar because water has hydrogen bonding and tends to dissolve substances that are polar  Oil and water are an example of two substance that do not mix  Oil is a mixture of nonpolar covalent compounds “Like dissolves Like”

7. See guidelines and answer the following… 1)Which is insoluble? LiCl, NaCl, AgCl or KCl 2)Which is soluble? Barium Sulfate or Potassium Sulfate 3)Which is insoluble? Potassium Carbonate or Zinc Carbonate 4)Which is soluble? Ammonium hydroxide or magnesium hydroxide Solubility Guidelines

8.  Relative amount of solute and solvent  Represented by [ ] Solution concentration

9. Concentrated- large amount dissolved in water (high concentration) Dilute- little amount dissolved in water (low concentration) Concentrated versus Dilute

10. UNSATURATED SOLUTION- amount of solute dissolved is less than the max that could be dissolved in the solution SATURATED SOLUTION- solution which holds the max amount of solute per amount of the solution under the given conditions Unsaturated versus Saturated

11. SUPERSATURATED SOLUTION contain more solute than the usual max amount  Unstable- cannot permanently hold the excess solute in solution and may release it suddenly  Usually created at elevated temperatures (higher solubility), then slowly cooled  Produce a large amount of crystalline solid if a small amount of solute is added (ex. Fudge) http://education-portal.com/academy/lesson/solubility-and- solubility-curves.html#lesson Unsaturated versus Saturated

12. Solubility Curve  Below the line soln is unsaturated  On or above the line soln is saturated Supersaturated? Example - How many grams of KCl can dissolve in 100g of water at 30C?

13. Temp has a significant effect on solubility The solubilities of MOST solutes increase with increasing temperature Unsaturated versus Saturated

14. Heat taken in or released in dissolving process For most solutes, the process of dissolving is an endothermic process – heat is written as a reactant Example: NH 4 NO 3 However, the dissolving of some solutes is exothermic – process releases heat Example: CaCl 2 HEAT OF SOLUTION

15. Molarity = moles of solute/ liter of solution M = moles / liter or mol/L Concentration example: 0.15 M NaCl = 0.15 moles of sodium chloride per liter of solution Concentration Unit

16. Need to know three things: 1) Concentration 2) Amount of solute 3) Total volume of solution needed http://education- portal.com/academy/lesson/calculating-molarity-and- molality-concentration.html#lesson To make a quantitative aqueous solution

17. 1. Weigh the solute 2. Transfer solute to a volumetric flask 3. Add enough water to dissolve solute (mix). 4. Bring the solution volume up to the calibration mark on the flask 5. Solution is shaken, stored and labeled Steps to Quantitative Solution Preparation

18. #7) How would you prepare 1.00 L of a 0.400 M solution of CuSO 4 ? Cu = 63.5 g/mol S = 32.1 g/mol 4 O = 16 x 4 = 64.0 g/mol CuSO4 = 159.6 g/mol 1.00 L soln x 0.400 m CuSO4 x 159.6 g CuSO4 1 L solution 1 mol CuSO4 = 63.8 g CuSO4 dissolve 63.8 g CuSO4 in 1.00 L solution Sample Solution Preparation Practice Problems p. 462

19. #8) How would you prepare 2.50 L of a 0.800 M solution of KNO 3 ? K = 39.098 g/mol N = 14.007 g/mol 3 O = 15.999 x 3 = 47.997 g/mol KNO 3 = 101.102 g/mol 2.50 L soln x 0.800 mol KNO 3 x 101.102 g KNO 3 1 L solution 1 mol KNO 3 = 202.2 g KNO 3 dissolve 202.2 g KNO 3 in 2.50 L solution Sample Solution Preparation Practice Problems p. 462

20. 12) What is the molarity of a soln that contains 14 g Na 2 SO 4 dissolved in 1.6 L soln? Na = 2 x 22.990 g/mol= 45.98 S = 32.066 g/mol 4 O = 15.999 x 4 = 63.996 g/mol Na 2 SO 4 = 142.042 g/mol 14 g Na 2 SO 4 x 1 mol Na 2 SO 4 = 0.062 mol Na 2 SO 4 / L 1.6 L soln 142.04 g Na 2 SO 4 or 0.062 M Na 2 SO 4 Calculating Molarity Practice Problem p. 463

21. #13) What is the molarity of a soln that contains 7.4 g NH 4 Cl dissolved in 820 mL soln? N = 14.007 g/mol 4 H = 4 x 1.008 = 4.032 g/mol Cl = 35.453 g/mol NH 4 Cl = 53.492 g/mol 7.4 g NH 4 Cl x 1 mol = 0.17 mol NH 4 Cl/ L 0.820 L soln 53.492 g NH 4 Cl or 0.17 M NH 4 Cl Calculating Molarity Practice Problem

22.  A solution has a lower FP than the corresponding pure solvent (less than 0ºC)  The amount that the FP is depressed relative to 0ºC depends on the concentration of the solute  An ionic solute produces greater depression of FP than a covalent one because it dissociates into ions (more ions to interfere with the freezing process) Ex: Ice cream, salt on sidewalks in winter Freezing-Point Depression

23.  BP of a solution is higher than the BP of a corresponding pure solvent (greater than 100ºC)  Solute interferes with the ability of the solvent particles to escape the liquid state – higher temperature is required to allow boiling  The higher the concentration of solute particles, the greater the boiling-point elevation Ex. Anti-freeze Boiling-Point Elevation

24.  The flow of solvent molecules through a selectively permeable membrane (higher solute to lower solute concentration)  Selectively permeable – allows certain materials to pass through them OSMOSIS

25.  The solubility of a gas in a liquid depends on the pressure of the gas pushing down on the liquid  The higher the pressure, the more soluble the gas  For solns of gases in liquids, gas solubility decreases as temp. increases (soda fizzes more when warm) Solutions of Gases in Water

26.  Mixtures that are between true solutions and heterogeneous mixtures  Contain particles that are evenly distributed through a medium and remain distributed over time – do not settle out  Colloid particles are 10-100x larger than typical ions or molecules dissolved in solutions COLLOIDS

27.  Light moving through a colloid is partially scattered and reflected by the dispersed particles- light scattering effect is called TYNDALL EFFECT  The light becomes visible and broadens. This occurs because colloid particles are about the same size as the wavelength of visible light (400 to 700 nm) COLLOIDS

28.  NameColorSolubility  CuCO3blu/grnInsol  Na2SO4colorlessSol  NaNO3colorlessSol  PbCO3whtInsol  BaCO3whtInsol  CuIbrn/whtinsol  I2brnInsol  PbI2yellowinsol  BaI2colorlesssol  PbSO4whtinsol  BaSO4whtinsol