24 Questions
What is the cause of non-wetting in a liquid-solid dispersion?
Insufficient uniform dispersion of solid particles
What determines the stability of a suspension in a liquid?
Balance of attractive & repulsive interactions between particles
What type of forces lead to attraction between particles in a dispersion?
Van der Waals forces
What leads to the thermodynamic instability of a system when particles are dispersed into a liquid?
Creation of a large interfacial area
Which type of system is characterized by charged particles of different sizes and gravity causing hard cake formation?
Deflocculated system
What type of forces predominate in a flocculated system?
Forces of attraction
What is the sedimentation volume when flocculation equilibrium is achieved?
1
What is the effect of increasing the concentration of KH2PO4 on the zeta potential?
Decreasing zeta potential
What is the rate of sedimentation/creaming according to the Stokes Equation?
$2a \cdot (\rho_p - \rho_m) \cdot g / 9\eta$
When does the rate of sedimentation/creaming become zero according to the Stokes Equation?
When $\rho_p = \rho_m$
What are the limitations of the Stokes Equation?
Applies only to spherical particles in a very dilute suspension
How can flocculation be controlled?
By adding electrolytes and/or polymers
What is colloidal stability defined as?
Thermodynamically stable solutions and coarse dispersions being unstable
How are particles protected to prevent aggregation?
By introducing repulsive interactions
What does the zeta potential measure?
The surface potential of particles
What forms when particle attraction occurs through weak and strong intermolecular forces?
Floccules and aggregates
What prevents the formation of a hard cake on the particle?
A repulsive or shielding barrier
What is responsible for the energy of attraction curve describing the variation in van der Waals force with distance?
Van der Waals forces
What is the role of steric in creating a repulsive barrier?
Using long chain polymers
What does the Electric Double Layer consist of?
Potential-determining ions and counterions
What is zeta potential dependent on?
The amount of counterion
What is the energy condition for particles to spontaneously decrease area and lead to phase separation?
$ riangle G > 0$
What is responsible for the electrical repulsion between particles being sensitive to counterions, their concentration, and valence?
Electric Double Layer
What is used to maintain electroneutrality and create a repulsive barrier?
Electric repulsion
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
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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