Physical Properties of Solutions
Physical Properties of Solutions Types of Solutions (13.1) A Molecular View of the Solution Process (13.2) Concentration Units (13.3) Effect of Temperature on Solubility (13.4) Effect of Pressure on the Solubility of Gases (13.5) Colligative Properties (13.6)
General Chemistry I Concepts Mixtures and representations of matter (1.3 and 1.4) Chemical formulas and nomenclature (2.6 and 2.7) Formula calculations particularly mole calculations and percent composition (3.3 and 3.5) Properties of solutions, introduction to hydration and concentrations of solutions (4.1 and 4.5) Enthalpy and heats of reaction (6.6) Intermolecular forces and vapor pressure (12.2 and 12.6)
13.1 Types of Solutions (Review 1.3 and 4.1) What is the definition of a mixture and how is this different from a pure substance? What are the definitions of solute, solvent and solution? How can you differentiate between a heterogeneous and homogeneous solution?
13.1 Types of Solutions Key Definitions: Unsaturated solutions: A solution that contains less solute than it has the capacity to dissolve. Saturated solutions: A solution that contains the maximum amount of a solute in a given solvent, at a specific temperature. Using sodium chloride in water describe how these are different. How would this be different for a solution of silver chloride?
13.1 Types of Solutions Key Definition: Supersaturated solutions: A solution that contains more solute than is present in a saturated solution. What is happening in the supersaturated solution shown in Figure 13.1? Figure 13.1 p. 440
13.2 A Molecular View of the Solution Process Consider the intermolecular forces between: solute/solute solvent/solvent solvent/solute Discussed in Chapter 12 intermolecular forces (12.2)
IMF Pure Substances Review: 12.2 Intermolecular Forces Interactions between: solute/solute solvent/solvent Dispersion forces Dipole forces Hydrogen bonding
Review:12.2 Intermolecular Forces IMF Mixtures Interactions between solute/solute and solvent/solvent: 1. Determine the intermolecular forces of the substances (usually considering the solubility of two pure substances) Approximating solubility 2. Determine the relative size of the two molecules (same or different) If both (IMF and size) are the same, then we would approximate that the substances are soluble If both (IMF and size) are different, then we would approximate that the substances are insoluble If one (IMF or size) are the same, then we would approximate that the substances are partially soluble
Review: 12.2 Intermolecular Forces IMF Mixtures Interaction between solvent/solute: Dispersion forces (or induced dipole-induced dipole) between all substances in a solution. A nonpolar and a polar substance would have induced dipole-dipole forces A polar and a polar substance would have dipole-dipole forces A ionic and a nonpolar substance would have ion-induced dipole forces A ionic and a polar substance would have ion-dipole forces
13.2 A Molecular View of the Solution Process Incorporating energy into the discussion Figure 13.2 p. 441
13.3 Concentration Units (Review 3.3, 3.5 and 4.5) What is molarity? Other types of concentration units: percent by mass molality mole fraction ppm
13.3 Concentration Units Concentrated sulfuric acid used in the lab is 96% H 2 SO 4 by mass. What is the molarity, molality and mole fraction of the acid solution? The density of the solution is 1.83 g ml 1.
13.4 Effect of Temperature on Solubility Consider two types of solutes: Solids (ionic) Gases (Review, 6.6) What is enthalpy of solution?
13.4 Effect of Temperature on Solubility ionic solids Solute ΔH soln kj mol 1 KNO 3 36.5 NaNO 3 21.56 NaBr 0.61 KBr 19.87 KCl 17.51 NaCl 3.87 Na 2 SO 4 5.02 Figure 13.3 p. 444
13.4 Effect of Temperature on Solubility ionic solids What does 100 g of potassium nitrate in 100 g water look like at 40 o C? What does this same mixture look like at 70 o C? Figure 13.3 p. 444
13.4 Effect of Temperature on Solubility gases Figure 13.4 p. 444
13.5 Effect of Pressure on the Solubility of Gases Pressure and solubility of liquids and solids Pressure and solubility of gases Using oxygen gas in solution (use water) describe what is the balanced equation? What would happen if we increase the pressure? What is the relationship between pressure and the solubility of gases?
13.5 Effect of Pressure on the Solubility of Gases Figure 13.5 p. 445
13.5 Effect of Pressure on the Solubility of Gases Pressure and solubility of gases What is the equation for Henry s law? Practice: The solubility of carbon dioxide in water at 25 o C and 1 atm is 0.034 mol L 1. What is the mass of carbon dioxide found in a 355 ml can of soda at 25 o C, assuming that the manufacturer used a pressure of 2.0 atm of carbon dioxide to carbonate the beverage? Does Henry s law always hold? When does it not?
13.6 Colligative Properties What are colligative properties? Vapor pressure lowering (Raoult s Law) Boiling-point elevation Freezing-point depression Osmotic pressure Why could these be useful? Will first discuss nonelectrolyte solutions
Vapor-pressure lowering (Raoult s Law) 13.6 Colligative Properties (Review, 12.6) What is vapor pressure? (Review 13.3) What is mole fraction? If something is nonvolatile, what does that mean? What is vapor pressure lowering?
Vapor-pressure lowering (Raoult s Law) 13.6 Colligative Properties Practice (nonvolatile solutions) The solubility of sugar in water at 25 o C is 67.47 mass fraction of sugar. What is the vapor pressure of water in this solution? Table 5.2 p. 156
Vapor-pressure lowering (Raoult s Law) 13.6 Colligative Properties (Review, 12.6) What is vapor pressure? (Review 13.3) What is mole fraction? If something is volatile, what does that mean? How does combining two volatile substances to form a solution affect the vapor pressures of each substance?
13.6 Colligative Properties Figure 13.6 p. 449 Figure 13.6 p. 449 Vapor-pressure lowering (Raoult s Law)
Vapor-pressure lowering (Raoult s Law) 13.6 Colligative Properties Practice (volatile solutions) Using figure 13.6, what is the vapor pressure of benzene at 80 o C? What is the vapor pressure of toluene at 80 o C? What is the total pressure when 50 g of toluene and 50 g of benzene are mixed? Figure 13.6 p. 449
13.6 Colligative Properties Boiling-Point Elevation (Review, 12.7) On a phase diagram where is the normal boiling point located? What happens at this point? Figure 12.32 p. 427
Boiling-Point Elevation 13.6 Colligative Properties (Review, 12.7) On a phase diagram where is the normal boiling point located? What happens at this point? (Review 13.3) What is molality? Why is molality better than molarity? What is boiling-point elevation? How is boiling-point elevation quantified?
13.6 Colligative Properties Figure 13.7 p. 449 Boiling-Point Elevation
13.6 Colligative Properties Boiling-Point Elevation Practice What is the boiling point of a saturated sugar solution (saturated at 25 o C)? At 25 o C, 67.47 mass fraction of the solution is sugar.
13.6 Colligative Properties Table 13.2 p. 450 Boiling-Point Elevation
13.6 Colligative Properties Freezing-Point Depression (Review, 12.1-12.4) What is the definition of a liquid versus a solid? Which has a greater disorder? (Review 13.3) What is molality? Why is molality better than molarity? What is freezing-point depression? How is freezing-point depression quantified?
13.6 Colligative Properties Figure 13.7 p. 449 Freezing-Point Depression
13.6 Colligative Properties Freezing-Point Depression Practice What is the freezing point of a saturated sugar solution (saturated at 0 o C)? At 0 o C, 64.447 mass fraction of the solution is sugar.
13.6 Colligative Properties Table 13.2 p. 450 Freezing-Point Depression
13.6 Colligative Properties Osmosis and Osmotic Pressure (Review, 13.1) What is vapor pressure? (Review, 12.6) What is osmosis?
13.6 Colligative Properties Figure 13.9 p. 453 Osmosis and Osmotic Pressure
13.6 Colligative Properties Osmosis and Osmotic Pressure (Review, 13.1) How do we model solutions on the particle level? (Review, 12.6) How do we model vapor pressure on the particle level? What happens if a semi-permeable membrane is placed between a solvent and a solution?
13.6 Colligative Properties Figure 13.8 p. 452 Osmosis and Osmotic Pressure
Osmosis and Osmotic Pressure 13.6 Colligative Properties (Review, 13.1) How do we model solutions on the particle level? (Review, 12.6) How do we model vapor pressure on the particle level? What happens if a semi-permeable membrane is placed between a solvent and a solution? What is osmosis and osmotic pressure How is osmotic pressure quantified?
13.6 Colligative Properties Osmosis and Osmotic Pressure Practice The molar mass of a type of hemoglobin was determined by osmotic pressure of 4.60 mmhg for a solution at 20 o C containing 3.27 g of hemoglobin in 0.200 L of solution. What is the molar mass of hemoglobin?
13.6 Colligative Properties Electrolyte Solutions What are colligative properties? Boiling-point elevation Freezing-point depression Osmotic pressure What do colligative properties depend on? Will now discuss electrolyte solutions
13.6 Colligative Properties Electrolyte Solutions How are nonelectrolytes and electrolytes different? (Review 2.6 and 2.7) How is a solution of calcium chloride different from sodium chloride? How is this incorporated into the relationships for colligative properties?
13.6 Colligative Properties Electrolyte Solutions Electrolyte solutions van t Hoff Factors Table 13.3 p. 457
13.6 Colligative Properties Electrolyte Solutions Why are the measured values not equal to the calculated values? What are ion pairs? Figure 13.11 p. 457
13.6 Colligative Properties Electrolyte Solutions Practice: What is the freezing point of a solution made by dissolving 10 g of sodium chloride in 100 g of water? What mass of magnesium chloride would be needed for the same change in freezing point?