Chapter 12 Solutions Georgia Gwinnett College Chem 1212K Spring 2011 B Shepler Chapter 12 1 Solutions Mixture Different types of atoms or molecules Not definite porportions Heterogeneous Observable boundaries between components Often represened by different phases but not always Not uniform Homogenous No observable boundaries Uniform Solutions not just liquid Solubility Chapter 12 2 Solutions and Solvation Solution A homogenous mixture of two or more substances that has no visible boundaries among its components The substances disperse into each other at the level of individual atoms molecules ions Two major components of a solution Solvent The substance present in the greater amount Solute The substance present in the lesser amount We say the solute dissolves in the solvent Solvation also dissolution The process of surrounding solute particles with solvent particles 3 Many Different Types of Solutions The solute and solvent can each be any combination of solid liquid gas Examples Solute Solvent Example Gas Gas Air in this room Liquid Liquid Ethanol and Water in alcoholic bev water and antifreeze Gas Liquid CO2 in soda Gas Solid H2 in metals hydrogen storage Solid Liquid sugar in iced tea 4 Nature s Tendency Toward Mixing Entropy Entropy A measure of energy randomization or energy dispersal In nature energy tends to spread out when it is not restrained from doing so Related to disorder on the molecular level Clean room will tend to get messy unless you expend energy to clean it Chapter 12 5 Solutions and Intermolecular Forces Intermolecular forces may promote or prevent the formation of a solution Intermolecular forces exist between all of the components of the solution Chapter 12 6 Intermolecular Forces Chapter 12 7 Example What would be the solute solute solvent solvent and solute solvent intermolecular forces in the following solutions Solute NaCl Solvent Water Solute Methane Solvent Benzene C6H6 Solute Ethanol Solvent Water Solute Methane Solvent Water Chapter 12 8 Energetics of Solution Formation Chapter 12 9 Chapter 12 10 Like Dissolves Like For a solution to form we must break the solute solute and solvent solvent interactions We make new solventsolute interactions Solutes tend to dissolve in solvents that have similar intermolcular forces Chapter 12 11 Practice Decide if the following are more soluble in hexane C6H14 or water naphthalene formaldehyde stearic acid 12 Solution Equilibrium Solubility the amount of solute we can dissolve in a given amount of solute Saturated Solution A solution in which the dissolved solute is in dynamic equilibrium with undissolved solute The maximum amount of solute has been disolved 13 Temperature and solubility of solids Chapter 12 14 Solubility of Gases Temperature Gas solubility decreases with increasing temperature More KE means the gases want to escape the solution Pressure Gas solubility increases with pressure In effect the higher pressure effectively forces the gases into solution Chapter 12 15