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Chemical reactions & Solutions

Chemical reactions & Solutions. Solutions. Homogeneous mixture 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

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Chemical reactions & Solutions

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  1. Chemical reactions&Solutions

  2. Solutions • Homogeneous mixture • 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. GSCI 163 Spring 2010

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

  4. 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 GSCI 163 Spring 2010

  5. 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. GSCI 163 Spring 2010

  6. Activity GSCI 163 Spring 2010

  7. Measuring • Moles/liter  molarity • Liters of solution (after mixing) • By mass fraction in percent GSCI 163 Spring 2010

  8. 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. GSCI 163 Spring 2010

  9. Activity Continued GSCI 163 Spring 2010

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