PHA 327 - Exam 2 - Disperse Systems 5

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kyleannkelsey
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PHA 327 - Exam 2 - Disperse Systems 5
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2013-04-21 21:20:17
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PHA 327 Exam Disperse Systems
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PHA 327 - Exam 2 - Disperse Systems 5
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  1. What type of Colloid dispersion can tolerate a moderate amount of electrolytes without coagulating or precipitating?
    Lyophilic
  2. What is salting out?
    When the addition of sufficient amount of electrolytes to a colloid solution can cause agglomeration and sedimentation
  3. Lyophilic colloid dispersion cannot tolerate electrolytes (T/F)?
    • False, they can tolerate a moderate amount of electrolytes
    • When too large a quantity of electrolytes is added to the dispersion, salting out occurs
  4. What type of Colloid dispersion is not thermodynamically stable?
    Lyophobic colloid
  5. The precipitating power that an electrolyte exerts on a colloid dispersion is based on what characteristic?
    The valence of the ion
  6. What does the addition of a small amount of electrolyte to a Lyophobic colloid dispersion achieve?
    Stabilization by providing a charge to the particles
  7. How would you stabilize a Lyophobic colloid dispersion?
    Add a small amount of electrolyte
  8. Calcium and Barium are more or less effective at precipitating an arsenious sulfide solution than Sodium and Potassium?
    • They are more
    • Calcium and Barium are divalent and Sodium and Potassium are Univalent
  9. Why are Calcium and Barium more effective at precipitating an arsenious sulfide solution than Sodium and Potassium?
    • Precipitating power of an electrolyte depends on the valence of the ion
    • Calcium and Barium are divalent and Sodium and Potassium are Univalent
  10. What is the Gold Number?
    mg of dry hydrophilic substance required to prevent a color change from red to violet in a Gold solution after adding 1mL of 10% NaCl
  11. What does a color change from red to violet when testing for the gold number indicate?
    A partial flocculation
  12. How could you determine the molecular weight of a colloid by its dispersion properties?
    By measuring light scattering
  13. Why would you m measure light scattering properties of a colloid dispersion?
    To determine the molecular weight of a colloid
  14. What is the Tyndall effect?
    When a light beam passes through a colloid dispersion and observed from a right agle, it appears cloudy
  15. What is Brownian motion?
    Random movement of particles in dispersion due to collisions
  16. What is diffusion?
    The movement of particles from areas of high concentration to areas of low concentration, to establish equilibrium
  17. Describe a Lyophobic Colloid:
    • Repulsion of the dispersion medium
    • Hydrophobic
  18. Describe an Association Colloid:
    Contains both polar and non-polar components (Amphiphilic)
  19. Are hydrophobic or hydrophilic colloidal dispersion easier to prepare?
    Hydrophilic
  20. What are the three methods for Preparing a hydrophobic colloidal dispersion:
    • Colloid mills and Ultrasonification
    • Condensation method
    • Dispersion method
  21. What is the Condensation method?
    • A method for preparing a hydrophobic colloid dispersion
    • It is achieved by a high frequency alternating current that is passed through a solvent
  22. What is the Dispersion Method?
    • A method for preparing a hydrophobic colloid solution
    • It is achieved by Mechanical and electrolytic disintegration
  23. Why would you use a Colloid mill, ultrasonification, the condensation method or the dispersion method?
    To prepare a Hydrophobic colloid solution
  24. Why is it important to remove as many dissolved ions from a colloid solution as possible?
    Presence of electrolytes in a colloid dispersion precipitates the colloid
  25. What material can cause the colloid to precipitate?
    Electrolytes
  26. What two ways can purification of a colloid dispersion be achieved?
    • Ultrafiltration
    • Dialysis
  27. Why would you perform ultrafiltration or dialysis of a colloid dispersion?
    To purify the colloid dispersion of electrolytes that may precipitate the colloid
  28. What type of colloids are thermodynamically stable?
    Lyophilic and Association Colloids

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