Chemical reactions & Solutions

September 15, 2015September 15, 2015September 15, 2015 GSCI 163 Spring 2010 Solutions  Homogeneous mixture gas, liquid or solid gas, liquid or solid  Solvent is the quantity in the LARGEST amount  Solute is the quantity in the SMALLEST amount  Solubility is the amount of solute per unit solvent at max.  Saturated  Maximum amount is dissolved  Supersaturated  More than the maximum. In some situations the release of excess requires a seed or starting point. A solution can then be temporarily supersaturated. Also true of water above the boiling point. It may not boil until you get the process started. Heat up water and add a salt. Cool the solution and if some salt doesn’t precipitate out the water may contain more molecules of salt than is normally possible.In some situations the release of excess requires a seed or starting point. A solution can then be temporarily supersaturated. Also true of water above the boiling point. It may not boil until you get the process started. Heat up water and add a salt. Cool the solution and if some salt doesn’t precipitate out the water may contain more molecules of salt than is normally possible.

September 15, 2015September 15, 2015September 15, 2015 GSCI 163 Spring 2010 Bonds Atomic forces  intramolecular  Bonding among the solute atoms Ionic, covalentIonic, covalent  Bonding among the solvent atoms Ionic, covalentIonic, covalent Forces between molecules  Intermolecular forces Bonding between the solute and solvent moleculesBonding between the solute and solvent molecules Several different types some stronger than others Several different types some stronger than others Water has hydrogen bonds (based on dipole-dipole) Water has hydrogen bonds (based on dipole-dipole) Strong bondStrong bond Ionic crystals (NaCl) ion-dipole [basic unit repeated] Ionic crystals (NaCl) ion-dipole [basic unit repeated] Covalent crystals Covalent crystals Van der Waals : dipole-dipole, induced dipole-dipole, dispersion (induced dipole –induced dipole)Van der Waals : dipole-dipole, induced dipole-dipole, dispersion (induced dipole –induced dipole)

September 15, 2015September 15, 2015September 15, 2015 GSCI 163 Spring 2010 Solutions  Depend on the relative attraction: Energy  Depends on the entropy Two different ideal gases are shown as colored balls. With no forces between the balls the gases mix due to entropy or the tendency of randomly moving objects to increase disorder. Top more ordered Bottom less ordered

September 15, 2015September 15, 2015September 15, 2015 GSCI 163 Spring 2010 Need to separate the solvent to insert the solute. For polar molecules (solute and solvent) the arrangement could allow for all molecules to be attracted via the electrostatic forces. However nonpolar molecules separating polar molecules have no mechanism to keep the solvent separated. Miscible: Some solutions are completely mixable so that you can add as much solute and solvent as you like. (Mixing of two gases) Immiscible: Some solutions never mix (oil and water) Like mixes with like Polar-polar Nonpolar-nonpolar Substances with similar intermolecular forces tend to dissolve in each other.

September 15, 2015September 15, 2015September 15, 2015 GSCI 163 Spring 2010 Activity

September 15, 2015September 15, 2015September 15, 2015 GSCI 163 Spring 2010 Measuring  Moles/liter  molarity Liters of solution (after mixing)Liters of solution (after mixing)  By mass fraction in percent

September 15, 2015September 15, 2015September 15, 2015 GSCI 163 Spring 2010 Water  Water is a polar molecule  Charge is not uniformly distributed.  Excess negative charge is found on the oxygen due to its ability to attract electrons. The attraction that results between neutral atoms with a negative charge excess at H is called hydrogen bonding. This attraction gives water many of its properties.

September 15, 2015September 15, 2015September 15, 2015 GSCI 163 Spring 2010 Activity Continued Cu Cl CuCl