PHA 327 - Exam 2 - Suspensions 3

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PHA 327 - Exam 2 - Suspensions 3
2013-04-22 00:23:04
PHA 327 Exam Suspensions

PHA 327 - Exam 2 - Suspensions 3
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  1. What is sedimentation volume (F)?
    • The ratio of the final volume of the sedimen (Vu) t to the original volume of the suspension (Vo)
    • F = Vu/Vo
  2. What value of F (sedimentation Volume) indicates that the suspension if in flocculated equilibrium and show no clear supernant on standing.
  3. What is the equation for Sedimentation Height?
    Sedimenation Height = Hultimate/Horigional
  4. What are the two interactive forces between particles in a suspension?
    • London forces (attractive)
    • Zeta potential (repulsive)
  5. What type of interactive force is the Zeta potential?
  6. What force in a suspension provides repulsion between particles?
    Zeta potential
  7. What type of interactive forces are London forces?
  8. What force in a suspension provides attractive interactions between particles?
    London forces
  9. What are London forces?
    Forces by which non-polar molecules induce polarity in each other
  10. What is the term for the situation where non-polar particles induce polarity in one another?
    London forces
  11. Is the Zeta potential or London forces stronger?
    Zeta potential
  12. When particles are dispersed by the Zeta potential, what is the term used to describe them?
  13. What two types of interactions between particles exist in a suspension?
    • Flocculation or Caking
    • Deflocculation
  14. Wht are loose aggregates of particles in a suspension called?
  15. What is a floc?
    A loose aggregate of particles in a suspension
  16. When a suspension is deflocculated how do repulsive and attractive forces compare?
  17. When a suspension is flocculated how do repulsive and attractive forces compare?
  18. What is a flocculating agent?
    An opposing ion to the adsorbate on the particle that increases attractive forces and causes flocculation
  19. When you continue adding the flocculating agents until its charge predominates, what happens?
    The repulsive forces will again predominate, resulting in deflocculation
  20. What are the four characteristics of a flocculated suspension?
    • Distinct boundary between supernant and sediment
    • Supernant is clear
    • Fluffy conglomerates (weakly bound)
    • Settles rapidly but no cake formation
  21. What are the five characteristics of a deflocculated suspension?
    • Repulsion is high energy
    • No distinct boundary between supernant and sediment
    • Cloudy supernant
    • Particles settle slowly
    • Cake formation over time which is very difficult to resuspend
  22. Does a deflocculated or flocculated suspension form a cake?
  23. Does a deflocculated of flocculated suspension have a cloudy supernant?
  24. What type of flocculated system is most preferred due to its stability advantage?
    Controlled flocculated suspension
  25. Why is a Controlled flocculated suspension preferred?
    It is more stable
  26. What are commonly used reducers of Zeta potential?
    • Electrolytes
    • Alcohols
  27. What is the most commonly used reducer of Zeta potential?
  28. What do surfactants do in a suspension?
    Forms an adsorbed monolayer on the particle surface
  29. What substances form an adsorbed monolayer on the outside of the particle surface in a suspension?
  30. What type of action do polymers have on suspensions?
    Protective colloid action