colligative properties

• VAPOR PRESSURE LOWERING

   Pressure exerted by the vapor being given off by a liquid at a given temperature

   Vapor Pressure is directly proportional to temperature

   Vapor pressure is lower among solutions with non-volatile solute (salt [NaCl], sugar [C12H22O11],

  potassium nitrate [KNO3] than in pure solvent

   This concept was observed by Francois Marie Raoult in 1887

   Expressed by Raoult’s Law = states that at constant temperature, the vapor pressure of the solvent over

  a solution is the product of the vapor pressure of the pure solvent, and the mole fraction of the solvent

  in a solution
• Colligative Properties

   Properties exhibited by solutions

   Dependent only by the number of particles dissolved in a given solvent

   Unaffected by the exact nature of the solute
• ΔTb = Boiling Point Elevation

  m= Molal Concentration / Molality

  Kb= Molal Boiling point constant of the solvent
• BOILING POINT ELEVATION

  The temperature at which a solution boils is higher than the boiling point of a pure solvent.
• Tb = Boiling Point of the solution

  ΔTb = Boiling Point Elevation

  T°b = Normal Boiling Point (constant) of the pure solvent
• FREEZING POINT LOWERING / DEPRESSION

  The temperature at which a solution freezes is lower than the freezing point of a pure solvent.
• ΔTf = Freezing Point Lowering

  m = Molal Concentration / Molality

  Kf = Molal Freezing Point at constant temperature of a solvent
• Tf = Freezing point of the solution

  T°f = Normal Freezing Point of the pure solvent

  ΔTf = Freezing Point Lowering
• Osmosis - The minimum external pressure that must be applied to a solution to prevent the diffusion of solvent from pure solvent into a solution.
• Π = Osmotic Pressure

  M = Molar Concentration / Molarity

  R = Ideal Gas Constant (0.0821 L− atm

  mol−K) OR 0.0821 L-atm/mol-K

  T = Absolute temperature or Temperature in Kelvin