Chem 102 Module 2: Solutions and Colligative Properties
Chem 102 Module 2: Solutions and Colligative Properties Chem 102
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This page Class Notes was uploaded by Lyna Nguyen on Tuesday February 9, 2016. The Class Notes belongs to Chem 102 at Texas A&M University taught by Dr. Bethel in Spring 2016. Since its upload, it has received 17 views. For similar materials see General Chemistry 2 in Chemistry at Texas A&M University.
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Date Created: 02/09/16
Module 2 Solutions and Colligative Properties 131 135 131 132 Units of Concentration m amount of solutemol per kilogram of solvent 0 Molality amount of solutemol mass of solventkg M 0 Not useful when dealing with most of colligative properties 0 Moles per liter of solution X amount of that componentNa divided by the total amount of all of the components 0 Mole fraction Na Na Nb mass of one component divided by the total mass of the mixture x 100 0 Common unit in consumer products 0 Parts per millionppm refers to relative quantities o solute and solvent by mass 1 ppm 10 g of substance in a sample with a total mass of 1 million g The Solution Process Why do solutions form 0 Factors Separate solute particles endothermic Separate solvent particles endothermic Solutesolvent interactions exothermic 0 Relative magnitude of AH determine overall heat of solution when the concentration of ions will not increase further and any additional solid added after this point will remain as a solid at the bottom of the break no change in amount 0 Example of dynamic equilibrium more solute can dissolve more solute dissolved than possible unstable concentration of solute in a saturated solution in equilibrium with undissolved solute Solvation process of solutes dissolving in solvents Liquids Dissolving in Liquids o 2 liquids that can be mixed in any proportion to form a homogenous mixture 0 do not fully mix in all proportions Exist with each other in layers Nonpolar liquids gt miscible Polar liquids gt miscible Polar nonpolar gt immiscible o Solids dissolving liquids Nonpolar solids nonpolar liquid gt readily Polar solids polar liquids gt readily Nonpolar solids polar liquids gt not so readily Polar solids nonpolar liquids gt not so readily lonic soluble in polar insoluble in nonpolar Solids dissolving in liquids o Nonpolar solids nonpolar liquids gt readily 0 Polar solids polar liquids gt readily o Nonpolar solids polar liquids gt not so readily 0 Polar solids nonpolar liquids gt not so readily 0 Network solids do not dissolve in water Enthalpy of Solution 0 Guidelines for quotlike dissolve likequot Entropy More entropy more favorable Enthalpy By viewing bonding forces 0 Non polar solute nonpolar solvent AH 0 o Ionic dissolving in water AH lt0 Guarantees soluble o highly exothermic Energy is evolved when ions dissolve where each ion is surrounded by water 0 Water soluble AH gt exothermic or only slightly endo o Enthalpy of solution Thermodynamic Data 0 Enthalpy of formations of solid liquid solution 133 Factors Affecting Solubility Pressure and Temperature 0 Dissolving Gasses in liquids Henry s Law P partial pressure S moikg K varies on solvent temperature dependent 0 Always exothermic 0 Pressure has no signi cant effect on solubility of liquids and solids Temperature Effects on Solubility le Chatelier s Principle 0 Solubility of gas in water decreases with increasing temperature 0 Gas liquid ltgt saturated solution energy a change in any factor determining an equilibrium causes the system to adjust by shifting in the direction that reduces or counteracts the effect of the change 134 Colligative Properties 0 properties that depend on the relative number of solute and solvent particles in a solution and not on their identities 0 Another de nition amount of solute particles 0 Only applies to solutions 0 Changes in Vapor Pressure Raoult s Law Module 2 Page 2 Final pressure is always less than pure solvent VP are additive ldeal solution obeys Raoult s law 0 Good approximation 0 For it to apply forces of attraction between solute and solvent must be the same 0 Boiling Point Elevation K molal boiling point constantsolvent O 0 Units Cm 0 Always positive l Vant Hoff Factor 0 1 molecular o Freezing Point Depression 0 Lower than pure solvent K freezing point depression constant Always negative values 0 AT lt0 decrease in temp Osmotic Pressure 0 movement of solvent molecules through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration Low gt high 0 measure of pressure created by the column of solution for the system at equilibrium greater than equal less than 0 Pi MRTi M molarity Colligative Properties and Molar Mass Determination 1 Use AT kmi a Calculate concentrate 2 Mol solute moikg kg solvent a Amount of solute 3 Molar mass g solutemol solute a Molar mass of unknown gmol o Colligative Properties of Solutions containing lons o ratio of experimentally observed dissociation of particles after split up For elevationdepression equations 135 Colloids represent a state intermediate between a solution and a suspension Module 2 Page 3 0 Higher molar masses 0 Particles are relatively large 0 Particles are suspended but not dissolved o Solute is dispersed solvent is continuous phase 0 Tyndall Effect Scatter visible light when dispersed in a solvent making the mixture appear cloudy 0 Do not settle o I solid in uid 0 structure that prevents it from being mobile 0 High surface areas because small size of the particles 0 Types of colloids colloids with water 0 Water fearing Weak forces water loving Strongly attracted to water one liquid in another 0 Emulsifying agents keeps them from separating 0 Also called emulsi er Surfactants Substances that affect the properties of surfaces and therefore affect the interaction between 2 phases 0 Lowers the tension of water Module 2 Page 4
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