solution process - like molecules dissolve like molecules

• ionic compounds dissolved in polar solvent (w/ ion-dipole forces)
• covalent compounds dissolved in nonpolar solvent (w/ dispersion forces)
• forces between solvent/solute must be greater than forces between solute molecules
• solvation - dissolving solute w/ solvent (solvent molecules completely surround solute)
  • hydration - solvation when solvent is water
• Hsoln = H1 + H2 + H3
  • H1 = separation of solute molecules (endothermic)
  • H2 = separation of solvent molecules (endothermic)
  • H3 = forming solvent-solute interactions (exothermic)
  • Hsoln can be either exothermic/endothermic
• no solution if too endothermic, spontaneous reaction if exothermic

spontaneous solution formation - usually exothermic

• energy decrease >> reaction starts spontaneously
• entropy/disorder increase >> reaction starts spontaneously (even if endothermic)
• molecules unrestrained >> spontaneous mixing occurs
• no solution of solute-solute or solvent-solvent forces greater than solvent-solute forces
• solute can change or remain unchanged after solvation

crystallization - opposite of solvation

• saturated solution - will not dissolve more solute if added
• solubility - amount of solute needed to form saturated solution
• unsaturated solution - dissolves less solute than in saturated solution
• supersaturated solution - contains more solute than needed for saturation
  • possible at different temperatures
  • very unstable, will crystallize w/ just a little bit of added solute

solute-solvent interactions - determines tendency of substances to mix

• stronger solute-solvent interaction >> greater solubility
• polar liquids dissolve polar solutes, don’t dissolve nonpolar solutes
• miscible - describes substances that dissolve in each other
• immiscible - describes substances that don’t dissolve in each other
• increase # of polar groups >> increase solubility in water