Colloidal Stability and Particle Interactions Quiz
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Questions and Answers

What is the cause of non-wetting in a liquid-solid dispersion?

  • Insufficient uniform dispersion of solid particles (correct)
  • Lack of gravitational effects
  • Excessive uniform dispersion of solid particles
  • Inadequate Brownian motion

    • What determines the stability of a suspension in a liquid?

  • Size of the particles in the suspension
  • Density of the liquid
  • Temperature of the liquid
  • Balance of attractive & repulsive interactions between particles (correct)

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

  • Electrostatic forces
  • Van der Waals forces (correct)
  • Gravitational forces
  • Magnetic forces

    • What leads to the thermodynamic instability of a system when particles are dispersed into a liquid?

    <p>Creation of a large interfacial area</p> Signup and view all the answers

    Which type of system is characterized by charged particles of different sizes and gravity causing hard cake formation?

    <p>Deflocculated system</p> Signup and view all the answers

    What type of forces predominate in a flocculated system?

    <p>Forces of attraction</p> Signup and view all the answers

    What is the sedimentation volume when flocculation equilibrium is achieved?

    <p>1</p> Signup and view all the answers

    What is the effect of increasing the concentration of KH2PO4 on the zeta potential?

    <p>Decreasing zeta potential</p> Signup and view all the answers

    What is the rate of sedimentation/creaming according to the Stokes Equation?

    <p>$2a \cdot (\rho_p - \rho_m) \cdot g / 9\eta$</p> Signup and view all the answers

    When does the rate of sedimentation/creaming become zero according to the Stokes Equation?

    <p>When $\rho_p = \rho_m$</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</p> Signup and view all the answers

    What is colloidal stability defined as?

    <p>Thermodynamically stable solutions and coarse dispersions being unstable</p> Signup and view all the answers

    How are particles protected to prevent aggregation?

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

    What does the zeta potential measure?

    <p>The surface potential of particles</p> Signup and view all the answers

    What forms when particle attraction occurs through weak and strong intermolecular forces?

    <p>Floccules and aggregates</p> Signup and view all the answers

    What prevents the formation of a hard cake on the particle?

    <p>A repulsive or shielding barrier</p> Signup and view all the answers

    What is responsible for the energy of attraction curve describing the variation in van der Waals force with distance?

    <p>Van der Waals forces</p> Signup and view all the answers

    What is the role of steric in creating a repulsive barrier?

    <p>Using long chain polymers</p> Signup and view all the answers

    What does the Electric Double Layer consist of?

    <p>Potential-determining ions and counterions</p> Signup and view all the answers

    What is zeta potential dependent on?

    <p>The amount of counterion</p> Signup and view all the answers

    What is the energy condition for particles to spontaneously decrease area and lead to phase separation?

    <p>$ riangle G &gt; 0$</p> Signup and view all the answers

    What is responsible for the electrical repulsion between particles being sensitive to counterions, their concentration, and valence?

    <p>Electric Double Layer</p> Signup and view all the answers

    What is used to maintain electroneutrality and create a repulsive barrier?

    <p>Electric repulsion</p> Signup and view all the answers

    Study Notes

    Colloidal Stability and Particle Interactions

    • ΔG > 0 causes particles to spontaneously decrease area, leading to phase separation
    • Particle attraction forms floccules and aggregates through weak and strong intermolecular forces
    • Colloidal stability is defined as thermodynamically stable solutions and coarse dispersions being unstable
    • To prevent aggregation, particles are protected by introducing repulsive interactions
    • Particle-particle attraction occurs at a certain distance due to Van der Waals forces
    • Energy of attraction curve describes the variation in van der Waals force with distance
    • A repulsive or shielding barrier on the particle prevents the formation of a hard cake
    • Repulsive barriers include steric (using long chain polymers) and electric (maintaining electroneutrality)
    • Zeta potential measures the surface potential of particles and is important for system stability
    • Electrical repulsion between particles is sensitive to counterions, their concentration, and valence
    • The Electric Double Layer and the importance of potential-determining ions and counterions
    • Zeta potential is dependent on the amount of counterion and is crucial for system stability

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    Description

    Test your knowledge of colloidal stability and particle interactions with this quiz. Explore concepts like ΔG, particle attraction, repulsive interactions, Van der Waals forces, zeta potential, and the Electric Double Layer. Understand how to prevent aggregation and maintain system stability in colloidal solutions.

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