Colligative properties

Colligative properties

1. A property of a solution that depends on the number of particles dissolved in the solution

   • They depend on the number of dissolved particles, not the type
   • There are four colligative properties: vapor pressure lowering, freezing point depression, boiling point elevation and osmotic pressure

2. Vapor Pressure Lowering

   • The vapor pressure of a solution is lower than the vapor pressure of the solvent
     • Raoult's law: Psolution= Xsolvent P˚solvent
     • At higher vapor pressure, the substance is more volatile
     • thanks to dynamic equilibrium

3. Freezing Point Depression

   • The freezing point of a solution is lower than the freezing point of the pure solvent
     • DeltaTf=imxKf
     • It contains a nonvolatile solute
       • The more concentrated the solution, the lower the freezing point will be

4. Boiling Point Elevation

   • The boiling point is higher than the boiling point of the pure solvent
     • DeltaTb=imxKb
     • It contains a nonvolatile solute

5. Osmotic Pressure

   • The pressure required to stop osmotic flow
     • Osmotic flow: the flow of solvent from a solution of lower solute concentration to one higher solute concentration
       • It occurs in an osmosis cell
     • π= iMRT

6. A strong electrolyte solution produces more of an effect on colligative properties than a nonelectrolyte solution of the same molar concentration

   • electrolytes
     • Dissociate in solution to produce a greater number of dissolved particles
   • Van't Hoff factor (i)
     • Is the ratio of moles of particles in a solution to moles of formula units dissolved
       • i= moles of particles in solution/moles of formula units dissolved

7. Medical Sector

   • Solutions are often administrated to patients, which have osmotic pressure greater than body fluids
     • They are called hyperosmotic
   • Solutions that have osmotic pressures less than body fluis pump water into cells
     • They are called hyposmotic
   • Intravenous solutions are administred directly into veins, having osmotic pressure equal to body fluids
     • They are called isosmotic