Colloids

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1. which of these is not a feature of a colloid?

  • Optical feature: Opalescent
  • Can be seen by electric microscope
  • Can be separated by electrophoresis because they often carry a charge
  • Allows dialysis
  • Contributes to the oncotic pressure
  • Because of their large size- they can induce light diffusion
  • > 500nm
  • settles by ultracentrifugation - cannot use filtration
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2. which is not true?

  • surfactants are compounds that increase surface tension (adhesive and cohesive forces)
  • when the monomer conc > CMC then a micelle is formed
  • there are 4 types of surfactants - anion, cationic, amphoteric, non ionic
  • Thin layer chromatography - separates substances with different affinity to 2 phases (staionary and mobile phase)

3. What is dialysis?

  • diffusion of small molecules and ions from the colloid across the dialysation membrane eg cellophane which is permeable to small molecules and not colloid perticlaes
  • The removal of waste products from the blood (purpose of an artificial kidney)
  • the electrophoretic mobility of the particles depends on the size , ccharge and shape.

4. Which purpose of the gel is correct?

  • Silica gel - chromatography, drying
  • Agarose gel - electrophoretic separation of protiens
  • polyacrylamind gel - electrophoretic separation of nucleic acids

5. what is a protective colloid?

  • A stubstance that specifically stabilises emulsions eg glycocholic (facilate absorption of dietary lipids)
  • A protective colloid are substances that form a hydrophilic colloid solution stabilizing the hydrophobic colloid particles.
  • A protective colloid are substances that form a hydrophobic colloid solution stabilizing the hydrophillic colloid particles.
  • proteins in the blood are protective colloids of Calcium phosphate and calcium carbonate leading to its precipitation (forming gall stones)

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