2046chapter13

2046chapter13 - 1 Chapter 13 Properties of Solutions...

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Unformatted text preview: 1 Chapter 13 Properties of Solutions Learning goals and key skills: h Understand the way enthalpy and entropy changes affect solution formation h Understand the relationship between intermolecular forces and solubility h Describe the effect of temperature on solubility of solids and gases h Describe the relationship between partial pressure of a gas and solubility h Be able to calculate concentration in molarity, molality, mole fraction, percent composition, and ppm. h Describe colligative properties h Be able to calculate vapor pressure of a solvent over a solution h Be able to calculate the boiling point elevation and freezing point depression of a solution h Be able to calculate the osmotic pressure of a solution Classification of Matter Classification of Matter Mixtures Mixtures Mixture Have variable composition and can be separated into component parts by physical methods. Mixtures contain more than one kind of molecule, and their properties depend on the relative amount of each component present in the mixture. Homogeneous Mixture (solution) Uniform composition. Gaseous solution air (N 2 , O 2 , CO 2 , etc) Liquid solution seawater (H 2 O, salts, etc) Solid solution brass (Cu and Zn) 2 Solutions Solutions Solutions are homogeneous mixtures consisting of a solvent and one or more solutes . In a solution, the solute is dispersed uniformly throughout the solvent . Solutions Solutions As a solution forms, the solvent pulls solute particles apart and surrounds, or solvates , them. The solute-solvent interactions compete with the solute-solute and solvent-solvent interactions. Aqueous solutions Aqueous solutions Aqueous solutions made from ionic salts have ion-dipole interactions that are strong enough to overcome the lattice energy of the salt crystal. For aqueous solutions, solute (H 2 O)-solvent interactions are referred to as hydration . 3 Energetics of solutions Energetics of solutions Energetics of solutions Energetics of solutions H soln = H 1 + H 2 + H 3 H soln for a solid dissolving in a liquid is usually slightly endothermic Entropy Entropy The reason is that increasing the entropy (i.e., disorder or randomness) of a system tends to lower the energy (not enthalpy) of the system. 4 Physical dissolution vs chemical reaction Physical dissolution vs chemical reaction Here is a single displacement/redox reaction: Ni (s) + 2 HCl (aq) NiCl 2 (aq) + H 2 (g) We cant get back the original Ni (or HCl) by physical methods, so this is NOT physical dissolution it is a chemical reaction ....
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This note was uploaded on 12/09/2011 for the course CHEM 1 taught by Professor Staff during the Summer '11 term at Simon Fraser.

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2046chapter13 - 1 Chapter 13 Properties of Solutions...

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