15 - The Chemistry of Solutes and Solutions

15 - The Chemistry of Solutes and Solutions - Chapter 15...

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Chapter 15: The Chemistry of Solutes and Solutions 15.1Solubility and Intermolecular Forces Types of solutions: o Gas in gas: air o Gas in liquid: carbonated beverages o Gas in solid o Liquid in liquid o Solid in liquid: ocean o Solid in solid: bronze Solute-Solvent Interactions o Dissolving a solute in a solvent is favored when the solute-solvent intermolecular forces are stronger than the solute-solute or the solvent-solvent intermolecular forces – like dissolves like o Miscible – liquids that dissolve in each other in any proportion o Immiscible – liquids with noncovalent attractions so different between their molecules that they do not dissolve in each other o Low-molar-mass alcohols dissolve in water due to hydrogen bonding between water molecules and the –OH group of alcohol; as hydrocarbon (hydrophobic) region grows larger, it resembles more of a nonpolar molecule London forces between hydrocarbons overpowers hydrogen bonding between solute-solvent o more than 6 carbons – insoluble in water o substances with similar noncovalent forces are likely to be soluble in each other o solutes do not readily dissolve in solvents whose noncovalent forces are quite different from their own o stronger solute-solvent attractions favor solubility; stronger solute-solute or solvent-solvent attractions reduce solubility o solids held together by networks of covalent bonds are insoluble in polar or nonpolar solvents o solubility in water or in triglycerides (fats) play important role in body – overdosing on fat-soluble vitamins is bad because vitamins are stored in fatty tissues and can accumulate to harmful levels 15.2Enthalpy, Entropy, and Dissolving Solutes 15.3Solubility and Equilibrium solubility of a solute is the maximum quantity of solute that dissolves in a given quantity of solvent at a particular temperature saturated solution is one whose solute concentration equals its solubility; dynamic equilibrium between dissolved and undissolved solute; Q=K c solute + solvent solute (in solution) K c =[solute (in solution)] unsaturated solution is one in which solute concentration is less than its solubility; Q < K c ; if solute continues to be added, solution will eventually become saturated supersaturated solution is one in which solute concentration is greater than its solubility; Q > K c ; solute is continuously added but is slow to precipitate back out to create a supersaturated solution; will precipitate until it is saturated Dissolving Ionic Solids in Liquids o lattice energy of the ionic compound is the enthalpy change when 1 mole of each ion is completely separated from a crystal lattice
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This note was uploaded on 09/28/2009 for the course CHEM 1A taught by Professor Nitsche during the Fall '08 term at Berkeley.

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15 - The Chemistry of Solutes and Solutions - Chapter 15...

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