Colloidal Stability and Particle Interactions Quiz
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Questions and Answers

What is the main cause of non-wetting in a liquid when solid particles are added?

  • Aggregation of solid particles in the liquid
  • Insufficient dispersion of solid particles in the liquid (correct)
  • Excessive dispersion of solid particles in the liquid
  • Sedimentation of solid particles in the liquid

    • What type of forces lead to attraction between particles in a liquid?

  • Ionic bonding
  • Electrostatic forces
  • Van der Waals forces (correct)
  • Hydrogen bonding

    • What causes the overall free energy of a system to increase when particles are dispersed into a liquid?

  • Increase in particle size
  • Decrease in particle density
  • Reduction in intermolecular forces
  • Creation of a large interfacial area (correct)

    • What is the main factor determining the stability of a suspension in a liquid?

    <p>Balance of attractive &amp; repulsive interactions</p> Signup and view all the answers

    What can greatly affect the zeta potential of particles and ultimately the stability of the system?

    <p>Electrolytes, pH, and other molecules that can adsorb to the interface</p> Signup and view all the answers

    What characterizes deflocculated particles?

    <p>Residing in primary minimum, high zeta potential, and repulsive forces exceeding attractive forces</p> Signup and view all the answers

    What does the sedimentation parameter F=1 indicate?

    <p>Flocculation equilibrium</p> Signup and view all the answers

    What is the Stokes Equation used for?

    <p>Calculating the rate of sedimentation/creaming for spherical particles in a dilute suspension</p> Signup and view all the answers

    What does the sedimentation rate v in the Stokes Equation depend on?

    <p>Particle size, density, and viscosity of the liquid</p> Signup and view all the answers

    What are the limitations of the Stokes Equation?

    <p>Applies only to spherical particles in a very dilute suspension</p> Signup and view all the answers

    How can flocculation be controlled?

    <p>By adding electrolytes and/or polymers to bring about flocculation</p> Signup and view all the answers

    What causes separation of phases in sedimentation and creaming?

    <p>Gravitational forces</p> Signup and view all the answers

    What is the main factor that defines colloidal stability?

    <p>Prevention of particle aggregation</p> Signup and view all the answers

    What is the role of weak intermolecular forces in colloidal systems?

    <p>Cause flocculation</p> Signup and view all the answers

    How can aggregation in dispersions be prevented?

    <p>Introducing repulsive interactions</p> Signup and view all the answers

    What is the significance of zeta potential in colloidal stability?

    <p>Measures surface potential and crucial for stability</p> Signup and view all the answers

    What influences the electrical repulsion between particles in dispersions?

    <p>Presence, concentration, and valence of counterions</p> Signup and view all the answers

    What plays a critical role in particle stability by forming repulsive barriers?

    <p>Electric double layer</p> Signup and view all the answers

    Where is the zeta potential measured?

    <p>At the shear plane</p> Signup and view all the answers

    What is the conventional belief about the position of the shear plane?

    <p>Close to the Stern plane</p> Signup and view all the answers

    What influences the zeta potential?

    <p>The potential-determining ion and the counterion</p> Signup and view all the answers

    What is the role of steric repulsive barriers in dispersions?

    <p>Prevent formation of hard cakes</p> Signup and view all the answers

    What is the significance of the electric double layer in colloidal stability?

    <p>Plays a critical role in particle stability</p> Signup and view all the answers

    What is the purpose of the repulsive interactions introduced in dispersions?

    <p>Overcome the thermodynamic tendency for aggregation</p> Signup and view all the answers

    Study Notes

    Colloidal Stability and Particle Interactions

    • Particles in a dispersion system tend to form agglomerates to decrease surface area, leading to phase separation
    • Flocculation occurs due to weak intermolecular forces, while aggregation is driven by stronger forces
    • Colloidal stability is defined by the prevention of particle aggregation in dispersions
    • To prevent aggregation, repulsive interactions must be introduced to overcome the thermodynamic tendency
    • Electric and steric repulsive barriers can prevent the formation of hard cakes in dispersions
    • Zeta potential measures the surface potential of particles and is crucial for stability
    • Electrical repulsion between particles is influenced by the presence, concentration, and valence of counterions
    • The electric double layer, including the Stern plane and shear plane, plays a critical role in particle stability
    • Zeta potential is dependent on the amount of absorbed counterions and is measured at the shear plane
    • Zeta potential is important for understanding and ensuring the stability of dispersed systems
    • The potential-determining ion and the counterion influence the zeta potential
    • The exact position of the shear plane is not known, but it is conventionally believed to be close to the Stern plane

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    Description

    Test your understanding of colloidal stability and particle interactions with this quiz. Explore concepts such as agglomeration, flocculation, and aggregation, and learn about the crucial role of zeta potential and electric double layer in preventing particle aggregation in dispersions.

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