Chapter 16: Lyophilic Colloids
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Questions and Answers

What is the main cause of Brownian motion?

  • Electric charge
  • Thermal bombardment (correct)
  • External application of force
  • Gravitational force
  • How does the velocity of particles change with decreasing particle size?

  • Remains constant
  • Decreases
  • Increases (correct)
  • Stops completely
  • What is the main driving force behind diffusion?

  • Gravitational force
  • Applied external force
  • Brownian movement (correct)
  • Electrically induced motion
  • What does Fick's first law relate to?

    <p>Change in concentration and distance traveled</p> Signup and view all the answers

    What type of colloids are systems containing colloidal particles that interact significantly with the dispersion medium?

    <p>Lyophilic colloids</p> Signup and view all the answers

    How are lyophilic colloidal sols usually obtained?

    <p>By dissolving the material in the solvent being used</p> Signup and view all the answers

    What is the term for the attachment of solvent molecules to the molecules of the dispersed phase in hydrophilic colloids?

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

    Which of the following materials produce lyophilic colloids in aqueous dispersion media?

    <p>Gelatin and acacia</p> Signup and view all the answers

    What does the negative sign in the equation for diffusion signify?

    <p>Diffusion occurs in decreasing concentration of diffusion</p> Signup and view all the answers

    Which particles diffuse faster in a given media?

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

    What is the relationship between osmosis and diffusion?

    <p>Osmosis involves transfer of solvent while diffusion involves passage of solute</p> Signup and view all the answers

    What does the van't Hoff equation π = cRT describe?

    <p>The osmotic pressure of a dilute colloidal solution</p> Signup and view all the answers

    What does the negative sign in the equation for diffusion signify?

    <p>Diffusion occurs in decreasing concentration of the diffusing material</p> Signup and view all the answers

    What is the van't Hoff equation used to calculate?

    <p>The osmotic pressure of a dilute colloidal solution</p> Signup and view all the answers

    In which type of media do smaller particles diffuse faster?

    <p>Molecular media</p> Signup and view all the answers

    What is the main action involved in osmosis?

    <p>Transfer of only the solvent</p> Signup and view all the answers

    What is the basis of classifying dispersed systems according to the mean particle diameter of the dispersed material?

    <p>Particle size</p> Signup and view all the answers

    Which types of dispersed systems are generally considered based on the size of the dispersed phase?

    <p>A. molecular dispersions, B. colloidal dispersions, C. atomic dispersions</p> Signup and view all the answers

    What is the size range assigned to colloidal dispersions?

    <p>1 - 1000 nm</p> Signup and view all the answers

    What is the dispersed material in dispersed systems?

    <p>Dispersed phase</p> Signup and view all the answers

    What characterizes lyophobic colloids?

    <p>They have little attraction for the dispersion medium.</p> Signup and view all the answers

    In which dispersion medium may a material form a lyophilic colloidal system?

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

    What is a characteristic of association or amphiphilic colloids?

    <p>They are characterized by having two distinct regions of opposing solution affinities within the same molecule or ion.</p> Signup and view all the answers

    What type of particles are generally found in lyophobic colloids?

    <p>Inorganic particles</p> Signup and view all the answers

    Which characteristic best describes colloidal dispersion based on particle size?

    <p>Visible under a normal microscope</p> Signup and view all the answers

    What technique can be used to separate colloidal particles from molecular particles?

    <p>Dialysis through a semipermeable membrane</p> Signup and view all the answers

    Which type of dispersion medium allows the formation of lyophobic colloidal systems?

    <p>Non-polar solvents</p> Signup and view all the answers

    What is the size range assigned to colloidal dispersions based on the text?

    <p>From 1 nm to 0.5 µm</p> Signup and view all the answers

    What are the factors affecting the sedimentation of particles in a dispersion medium?

    <p>Particle size, viscosity, and density difference between particles and dispersion medium</p> Signup and view all the answers

    What is the lower size limit of particles obeying Stokes's equation when subjected only to the force of gravity?

    <p>0.5 µm</p> Signup and view all the answers

    What device is used to produce a force one million times that of gravity to bring about the sedimentation of colloidal particles?

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

    What promotes mixing instead of sedimentation due to gravity for particles below the lower size limit obeying Stokes's equation?

    <p>Brownian movement</p> Signup and view all the answers

    What is the term for the process in which dispersed particles come together to form aggregates over a narrow concentration range?

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

    In which type of colloidal dispersion would the diameter of each micelle be approximately 50 Å?

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

    What is the main effect on the viscosity of the dispersion medium when lyophobic colloidal particles are present?

    <p>Viscosity is not greatly increased because the particles tend to be unsolvated and symmetric</p> Signup and view all the answers

    What is the term for the primary cause of the desolvation of lyophilic molecules in the presence of high concentrations of very soluble electrolytes?

    <p>Salting out</p> Signup and view all the answers

    In which type of dispersion system does the critical micelle concentration decrease with the addition of electrolytes in aqueous solutions?

    <p>Association (Amphiphilic)</p> Signup and view all the answers

    What is the term for the process where a sol may become a gel at sufficiently high concentrations of dispersed phase?

    <p>Gel formation</p> Signup and view all the answers

    What property generally characterizes lyophobic colloids in the presence of electrolytes?

    <p>Instability due to neutralization of the charge on the particles</p> Signup and view all the answers

    What is the term for when colloidal aggregates are formed spontaneously when the concentration of amphiphile exceeds a certain value?

    <p>Salting out</p> Signup and view all the answers

    What happens to the velocity of particles as micelles increase in number and become asymmetric in an association (amphiphilic) dispersion?

    <p>The velocity increases</p> Signup and view all the answers

    What is the term for when dispersed particles come together to form aggregates over a narrow concentration range?

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

    What is the term for the process that causes lyophobic dispersions to be unstable in the presence of even small concentrations of electrolytes?

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

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