CHAPTER 13 PROPERTIES OF SOLUTIONS ADVANCED CHEMISTRY OBJECTIVES

CHAPTER 13: PROPERTIES OF SOLUTIONS ADVANCED CHEMISTRY

OBJECTIVES Analyze the solution process in terms of solute-solute, solute-solvent, and solvent-solvent interactions. Describe how enthalpy and entropy changes affect solution formation to explain solution formation energetics. Describe the relationship between intermolecular forces and solubility, including use of the “like dissolves like” rule. Describe the effect of concentration, temperature and pressure on solubility. Describe and calculate the concentration of a solution in terms of molarity, molality, mole fraction, percent composition, and parts per million and be able to interconvert between them. Describe what a colligative property is and explain the difference between the effects of nonelectrolytes and electrolytes on colligative properties. Define the van't Hoff factor, i. Describe the effect of solute (or solvent) concentration on each colligative property—vapor pressure, boiling point, freezing point, osmotic pressure and calculate any of these effects from concentration data. Observe colligative properties of solution (boiling point elevation, freezing point depressions) and use them to determine the molar mass of a substance [PA]. Calculate the concentration and molar mass of a nonvolatile, nonelectrolyte from its effect on a colligative property. �Explain the difference between a solution and a colloid.

THE SOLUTION PROCESS Solutions are homogeneous mixtures of two or more pure substances In a solution, the solute is dispersed uniformly throughout the solvent Formation of solutions is enhanced by increasing the entropy that accompanies mixing; the entropy of the system is increased while its enthalpy is reduced

INTERMOLECULAR FORCES AND SOLUTION FORMATION During a solution formation, three intermolecular interactions need to be considered Solvent-solvent: must be overcome to make room for solute particles to bond with solvent particles (endothermic) Solute-solute: must be overcome to make room for solvent particles to bong with solute particles (endothermic) Solvent-solute: the intermolecular forces between the dissociated solvent and solute particles (exothermic) To form solutions, the solute particles need to be completely surrounded by the solvent molecules, this process is known as solvation. (hydration when surrounded by water molecules)

ENERGETICS OF SOLUTION FORMATION

SOLUTION FORMATION AND CHEMICAL REACTION If a solute disappears when it comes to direct contact with a solvent, it may have dissolved or reacted If the solute can’t be retrieved back by evaporation, then it had reacted If the solute can be retrieved back by evaporating the solvent, it has dissolved. This process is called dissolution, the process of solute forming solution upon interaction with the solvent

SATURATED SOLUTIONS AND SOLUBILITY In a saturated solution, the solvent holds as much solute as it can at that temperature In an unsaturated solution, less solute can dissolve in the solvent at that temperature In a super saturated solution, the solvent holds more solute than is normally possible at that temperature Crystallization occurs when a dissolved solute comes out of solution by forming crystals

FACTORS AFFECTING SOLUBILITY Solute-Solvent Interactions Pressure Effects Temperature Effects

FACTORS AFFECTING SOLUBILITY (SOLUTE-SOLVENT INTERACTIONS) When the attractions between the solute and solvents are greater, the solubility is greater Polar molecules tend to dissolve in polar solvents and non-polar molecules tend to dissolve in non-polar solvents Glucose is miscible in water, means glucose is soluble in water Oil is immiscible in water, means oil is not soluble in water

FACTORS AFFECTING SOLUBILITY (PRESSURE EFFECTS)

FACTORS AFFECTING SOLUBILITY (TEMPERATURE EFFECTS) Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature The solubility of gas solutes in liquid solvents decreases with increasing temperature The carbonated water in the cold water will be more “bubbly” than the carbonated water in the hot water

EXPRESSING SOLUTION CONCENTRATION

MOLE FRACTION, MOLARITY AND MOLALITY

COLLIGATIVE PROPERTIES OF AQUEOUS SOLUTIONS Colligative properties are properties that are influenced by the number of solute particles, irrespective of their nature Colligative properties include: Vapor pressure lowering Boiling point elevation Melting point depression Osmotic pressure

VAPOR PRESSURE LOWERING

BOILING POINT ELEVATION

FREEZING POINT DEPRESSION

OSMOTIC PRESSURE

COLLIGATIVE PROPERTIES OF ELECTROLYTE SOLUTIONS

COLLOIDS Colloids are dispersion of particles of one substance in a dispersing medium Aerosol: solid or liquid dispersed in a gas Emulsion: liquid dispersed in a liquid Sol: solid dispersed in a liquid Tyndall effect: the scattering of light which takes place with colloids and aerosols

REFERENCES 1. Lecture: Theodore E. B. , Eugene, H. L. H. , Bruce E. B. , Catherine M. , Patrick W. , (2011). Chemistry: The Central Science (12 Ed). Prentice Hall. USA. 2. Laboratory: Theodore E. B. , John H. N. , Kenneth C. K. , Matthew S. (2011). Laboratory Experiments for Chemistry: The Central Science (12 Ed). Prentice Hall. USA. 3. Theodore E. B. , (2011). Solutions to Exercises for Chemistry: The Central Science. Prentice Hall. USA. 4. John M. , Robert C. F. (2010). Chemistry (4 Ed): Prentice Hall Companion Website. http: //wps. prenhall. com/esm_mcmurry_chemistry_4/9/2408/616516. cw/index. html 5. Chemistry Online at http: //preparatorychemistry. com/Bishop_Chemistry_First. htm 6. Chemistry and You at http: //www. saskschools. ca/curr_content/science 9/chemistry/index. html 7. Teachers Notes