CHEM 2

• Colligative properties


  Properties that depend only on the number of dissolved particles (molecules or ions, small or large) in solution and not on their identity
• Colligative properties


  • Osmotic Pressure
  • Vapor pressure Lowering
  • Boiling point elevation
  • Freezing Point depression

  
• Raoult's Law


  The partial vapor pressure of each component of an ideal mixture of liquid equals the vapor pressure of the pure component multiplied by the mole fraction of the mixture

  
• Vapor pressure lowering


  When a non-volatile solute is dissolved in a solvent, the vapor pressure of the solvent is lowered. Solvent molecules on the surface which can escape are replaced by solute molecules that have little (if any) vapor pressure.

  
• Vapor pressure lowering is a colligative property because it only depends on the number of dissolved solute particles.

  
• Boiling point elevation


  The boiling point of a liquid is defined as the temperature at which the vapor pressure of that liquid equals the atmospheric pressure (760mm Hg). For a solution, the vapor pressure of the solvent is lower at any given temperature, so a higher temperature is required to boil the solution than the pure solvent.

  
• Freezing point depression


  The normal freezing or melting point is the temperature at which the solid and liquid are in equilibrium under 1 atm. Addition of a solute will decrease the vapor pressure and so will decrease the freezing point.

  
• Osmosis


  The diffusion of solvent through a semi-permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

  
• Thermochemistry


  The study of energy changes that accompany physical and chemical processes, including the measurement and prediction of energy changes.
• Thermochemical equation


  A chemical equation that includes the amount of energy, in the form of heat transferred, in the reaction.
• Exothermic reaction


  A reaction that gives off heat, so the energy of the surroundings is increased and the energy of the system has decreased.
• Endothermic reaction


  A reaction that absorbs heat, so the system is increasing in heat energy.
• Enthalpy (ΔH)


  A thermodynamic property of a system that is the sum of the internal energy and the product of pressure and volume.
• First Law of Thermodynamics


  The internal energy of a system is equal to the work done on the system plus or minus the heat flow, and energy can be converted from one form to another.
• Calorimetry


  The process of measuring the amount of heat released or absorbed during a chemical reaction.
• Calorimeter


  A device that measures heat flow, using water as a standard.
• Chemical equilibrium


  A dynamic state in which two opposing processes occur at equal rates.
• Equilibrium constant (K)


  The ratio of the rate of the forward reaction to the rate of the backward reaction.
• Reaction quotient (Q)


  The ratio of the concentrations of products and reactants, used to predict the direction of a reaction.
• Factors affecting equilibrium


  • Concentration of reactants and/or products
  • Pressure
  • Heat evolution/absorption
  • Temperature
• Le Chatelier's Principle


  If a stress is applied to an equilibrium system, the system will readjust to minimize the stress.