interfacial tension

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interfacial tension
2013-04-25 09:34:28
DD3 final

DD3 final
Show Answers:

  1. what happens to surface tension of the system with positive adsorption?
  2. relationship between conc at interface and conc at bulk with positive adsorption
    conc interface > con at bulk
  3. what does wetting agent do to the contact angel when dissolved
    dec contact angle
  4. which ions are in the tightly bound layer of an electrical double layer
    the potential determining ions
  5. which ions are at the diffuse layer
    an excess of the counter ions to the ones in the tightly bound layer
  6. what ions are in the electrically neutral layer
    there is a balance of determining and counter ions
  7. nerst potential
    electrothermodynamic potential: diff in potential btwn solid surface and electroneutral region
  8. zeta potential
    electrokinetic potential: diff in potential between shear plane (tightly bound plane) and electroneutral region
  9. what does the zeta potential determine
    the degree of repulsion between particles of like charge
  10. if zeta potential falls below a certain value what happens?
    particle aggregation - flocculation
  11. 2 ways to reduce the surface free energy and make a more thermodynamically stable state
    • reduce interfacial tension with a surfactant
    • dec the interfacial surface area through flocculation

    we don't want flocculation, so use a surfactant
  12. deflocculated particles
    they don't aggregate, rather they just settle to the bottom (bigger ones first and then smaller ones) and the smaller ones begin to fill in all the crevices that the bigger ones leave and that forms a hard cake
  13. 3 assumptions of sedimentation theory
    • use stokes law
    • dilute suspension
    • distinct boundary between the sediment and surfactant
  14. what is the sedimentation volume
    ratio of final volume of sediment to original volume
  15. when will F be greater than 1?
    when the network of flocs occupy a greater volume than the original volume