Understanding the kinetic properties of colloids is essential for B. Pharm students working on formulations, suspensions, emulsions and drug delivery systems. This concise guide focuses on diffusion, Brownian motion, sedimentation, electrophoresis and zeta potential—key concepts that determine colloidal stability and performance. Emphasis on pharmaceutical relevance, measurement techniques (light scattering, ultracentrifugation, dialysis) and practical factors (particle size, viscosity, ionic strength, temperature) helps bridge theory and lab practice. Keyword-rich coverage ensures relevance for exam prep and online searches: kinetic properties of colloids, colloidal stability, Brownian motion, diffusion coefficient, zeta potential, pharmaceutical formulations, MCQs with answer. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary cause of Brownian motion in colloidal particles?
- Gravitational forces acting on the particle
- Random collisions with solvent molecules
- Electrostatic attraction between particles
- Magnetic fields in the medium
Correct Answer: Random collisions with solvent molecules
Q2. Which equation relates diffusion coefficient (D) to temperature (T), viscosity (η) and particle radius (r)?
- Stokes-Einstein equation
- Van’t Hoff equation
- Arrhenius equation
- Poiseuille’s law
Correct Answer: Stokes-Einstein equation
Q3. In Stokes-Einstein equation D = kT / (6πηr), what happens to D when particle radius doubles, assuming other factors constant?
- D doubles
- D remains unchanged
- D halves
- D quadruples
Correct Answer: D halves
Q4. Which technique is commonly used to measure particle size distribution in colloids via light scattering?
- Dynamic light scattering (DLS)
- Viscometry
- Ultrafiltration
- Electrophoresis
Correct Answer: Dynamic light scattering (DLS)
Q5. The Tyndall effect in colloids is due to:
- Absorption of light by particles
- Scattering of light by particles
- Emission of light by solvent molecules
- Reflection from container walls
Correct Answer: Scattering of light by particles
Q6. Zeta potential is most directly related to which colloidal property?
- Color of the colloid
- Colloidal stability against aggregation
- Boiling point elevation
- Viscosity only
Correct Answer: Colloidal stability against aggregation
Q7. In electrophoresis, colloidal particles move due to:
- Temperature gradients
- Applied electric field
- Magnetic resonance
- Shear stress
Correct Answer: Applied electric field
Q8. Which theory explains stability of colloids by balance of van der Waals attraction and electrostatic repulsion?
- DLVO theory
- Hard-sphere model
- Arrhenius theory
- Langmuir adsorption theory
Correct Answer: DLVO theory
Q9. What is peptization in colloid chemistry?
- Conversion of a stable colloid to a precipitate
- Aggregation caused by adding electrolyte
- Dispersing aggregated particles into colloidal state using a peptizing agent
- Coalescence of droplets in an emulsion
Correct Answer: Dispersing aggregated particles into colloidal state using a peptizing agent
Q10. Which factor does NOT generally increase Brownian motion intensity for a colloidal particle?
- Higher temperature
- Smaller particle size
- Lower viscosity
- Greater particle mass
Correct Answer: Greater particle mass
Q11. Sedimentation velocity of colloidal particles is best predicted by which law (under laminar conditions)?
- Stokes’ law
- Fick’s first law
- Henry’s law
- Nernst equation
Correct Answer: Stokes’ law
Q12. Which parameter is directly measured to estimate zeta potential experimentally?
- Diffusion coefficient
- Electrophoretic mobility
- Sedimentation rate
- Optical absorbance
Correct Answer: Electrophoretic mobility
Q13. The Smoluchowski equation is used to relate electrophoretic mobility to:
- Particle density
- Zeta potential
- Viscosity only
- Dielectric constant only
Correct Answer: Zeta potential
Q14. Which is an example of a lyophilic colloid relevant to pharmaceuticals?
- Gold sol
- Gelatin sol
- Silica in water
- Mercury droplets
Correct Answer: Gelatin sol
Q15. Ostwald ripening in emulsions refers to:
- Droplet coalescence due to shear
- Growth of larger droplets at expense of smaller ones due to solubility differences
- Immediate phase inversion
- Electrostatic stabilization of droplets
Correct Answer: Growth of larger droplets at expense of smaller ones due to solubility differences
Q16. Which method separates colloidal particles based on size and density using high centrifugal force?
- Dialysis
- Ultracentrifugation
- Gel filtration chromatography
- pH titration
Correct Answer: Ultracentrifugation
Q17. What effect does increasing ionic strength typically have on a charged colloidal system?
- Increases electrostatic repulsion
- Screens charges and promotes aggregation
- Turns the colloid lyophilic
- Reduces particle size
Correct Answer: Screens charges and promotes aggregation
Q18. The diffusion of colloidal particles from high to low concentration is described by:
- Fick’s laws
- Hooke’s law
- Raoult’s law
- Beer’s law
Correct Answer: Fick’s laws
Q19. Which property increases with decreasing particle size for spherical colloids, affecting reaction rates and adsorption?
- Surface area to volume ratio
- Bulk density
- Magnetic susceptibility
- Solubility in nonpolar solvents
Correct Answer: Surface area to volume ratio
Q20. Protective colloids stabilize lyophobic sols mainly by:
- Increasing ionic strength
- Forming a steric barrier around particles
- Decreasing viscosity drastically
- Absorbing light to prevent heating
Correct Answer: Forming a steric barrier around particles
Q21. In a pharmaceutical suspension, flocculation is usually preferred over deflocculation because:
- Flocculated suspensions settle slowly and are hard to redisperse
- Flocculated systems form a compact cake
- Flocculated suspensions settle rapidly but are easily redispersible
- Deflocculated suspensions have better taste
Correct Answer: Flocculated suspensions settle rapidly but are easily redispersible
Q22. Which measurement indicates kinetic stability against creaming in emulsions?
- Viscosity only
- Zeta potential alone
- Creaming index and droplet size distribution
- pH value only
Correct Answer: Creaming index and droplet size distribution
Q23. Smoluchowski’s theory primarily addresses which kinetic process in colloids?
- Electrostatic stabilization
- Coagulation rate due to Brownian motion
- Ostwald ripening kinetics
- Diffusion across membranes
Correct Answer: Coagulation rate due to Brownian motion
Q24. Which factor increases the rate of sedimentation according to Stokes’ law?
- Decreasing particle density difference
- Increasing medium viscosity
- Increasing particle radius
- Reducing gravity
Correct Answer: Increasing particle radius
Q25. The electrophoretic mobility of a colloidal particle is defined as:
- Velocity per unit electric field
- Acceleration per unit mass
- Charge per unit volume
- Force per unit charge
Correct Answer: Velocity per unit electric field
Q26. Dialysis of colloidal dispersions is used to remove:
- Large colloidal particles
- Small ions and low molecular weight solutes
- Emulsifying agents permanently bound to particles
- Solid contaminants only
Correct Answer: Small ions and low molecular weight solutes
Q27. Which term describes a colloid that is attracted to the solvent (solvent-loving)?
- Lyophobic
- Lyophilic
- Hydrophobic
- Hydrophobic-lipophilic balance
Correct Answer: Lyophilic
Q28. Which experimental technique can directly measure zeta potential and particle mobility?
- UV-Vis spectrophotometry
- Electrophoretic light scattering (ELS)
- Gas chromatography
- Titration with strong base
Correct Answer: Electrophoretic light scattering (ELS)
Q29. A high absolute value of zeta potential (positive or negative) generally indicates:
- Unstable colloid with fast aggregation
- Stable colloid with electrostatic repulsion
- Neutral colloid with no charge
- Immediate precipitation
Correct Answer: Stable colloid with electrostatic repulsion
Q30. Which is a kinetic method to accelerate coagulation for testing colloidal stability?
- Adding a stabilizing polymer
- Adding electrolyte (salt)
- Lowering temperature to absolute zero
- Reducing particle concentration to zero
Correct Answer: Adding electrolyte (salt)
Q31. In Fick’s first law, flux is proportional to:
- Concentration gradient
- Total concentration only
- Viscosity squared
- Temperature squared
Correct Answer: Concentration gradient
Q32. Which parameter is most important in predicting the rate of diffusion of a nanoparticle in solution?
- Particle color
- Diffusion coefficient
- Magnetic moment
- Optical refractivity
Correct Answer: Diffusion coefficient
Q33. Which stabilizing mechanism is dominant for sterically stabilized colloids?
- Electrostatic repulsion due to double layer
- Steric hindrance by adsorbed polymer chains
- Van der Waals attraction
- Magnetic repulsion
Correct Answer: Steric hindrance by adsorbed polymer chains
Q34. Which process describes the reversible aggregation where particles form loose flocs held by weak forces?
- Coagulation (irreversible)
- Flocculation (reversible)
- Solvation
- Covalent cross-linking
Correct Answer: Flocculation (reversible)
Q35. The rate constant for diffusion-controlled coagulation is most influenced by:
- Solvent color
- Temperature and viscosity
- Particle taste
- Container material only
Correct Answer: Temperature and viscosity
Q36. Which colloidal system is commonly used for targeted drug delivery and shows significant kinetic behavior due to Brownian motion?
- Microscale tablets
- Liposomes and polymeric nanoparticles
- Bulk crystalline powders
- Compressed pellets
Correct Answer: Liposomes and polymeric nanoparticles
Q37. The electrical double layer around a colloidal particle comprises:
- Stern layer and diffuse layer
- Monolayer of covalent bonds only
- Only adsorbed gases
- Solid crust and liquid core
Correct Answer: Stern layer and diffuse layer
Q38. Which observation indicates a colloid is approaching coagulation on zeta potential measurement?
- Zeta potential magnitude increases significantly
- Zeta potential approaches zero
- Zeta potential becomes very negative or positive beyond ±80 mV
- Zeta potential shows oscillatory behavior
Correct Answer: Zeta potential approaches zero
Q39. Which of the following increases emulsion stability by reducing interfacial tension and providing a barrier to coalescence?
- Surfactants and emulsifiers
- Adding coarse sand
- Applying UV radiation
- Increasing ambient pressure only
Correct Answer: Surfactants and emulsifiers
Q40. Which kinetic phenomenon can be monitored by measuring changes in turbidity over time?
- Coagulation and flocculation rates
- Chemical synthesis of polymers only
- pH stability but not aggregation
- Electrical conductivity exclusively
Correct Answer: Coagulation and flocculation rates
Q41. The term “critical coagulation concentration (CCC)” refers to:
- Minimum particle concentration to form a colloid
- Minimum electrolyte concentration required to induce rapid coagulation
- Maximum polymer concentration for steric stabilization
- Salt concentration giving maximum zeta potential
Correct Answer: Minimum electrolyte concentration required to induce rapid coagulation
Q42. Which factor reduces the diffusion coefficient of colloidal particles?
- Increasing temperature
- Decreasing particle size
- Increasing medium viscosity
- Decreasing solvent density only
Correct Answer: Increasing medium viscosity
Q43. In pharmaceutical suspensions, which excipient often acts as a protective colloid to stabilize particles?
- Sodium chloride
- Polyvinylpyrrolidone (PVP)
- Hydrochloric acid
- Activated charcoal
Correct Answer: Polyvinylpyrrolidone (PVP)
Q44. Which kinetic parameter describes how quickly particles move due to Brownian motion relative to sedimentation?
- Schmidt number
- Peclet number
- Reynolds number
- Biot number
Correct Answer: Peclet number
Q45. Which statement about nanoparticles in suspension is correct regarding kinetic stability?
- Smaller nanoparticles always sediment faster than larger ones
- Brownian motion can overcome sedimentation for sufficiently small particles
- Higher density difference reduces Brownian motion intensity
- Zeta potential has no role in nanoparticle stability
Correct Answer: Brownian motion can overcome sedimentation for sufficiently small particles
Q46. Which method quantifies particle size by measuring time-dependent fluctuations in scattered light intensity?
- Static light scattering (SLS)
- Dynamic light scattering (DLS)
- Gas adsorption
- Electrochemical impedance
Correct Answer: Dynamic light scattering (DLS)
Q47. Which of the following reduces Ostwald ripening in emulsions?
- Using highly soluble dispersed phase
- Minimizing surfactant concentration
- Using dispersed phase components with low solubility in continuous phase
- Increasing temperature dramatically
Correct Answer: Using dispersed phase components with low solubility in continuous phase
Q48. The kinetic stability of a colloid can be assessed by measuring:
- Rate of change in particle size and turbidity over time
- Only the initial color of the dispersion
- Magnetic resonance of solvent
- Electrical resistance of the container
Correct Answer: Rate of change in particle size and turbidity over time
Q49. Which of the following best describes “coalescence” in emulsions?
- Formation of smaller droplets from larger ones
- Merging of droplets to form larger droplets
- Evaporation of dispersed phase
- Electrostatic repulsion increase
Correct Answer: Merging of droplets to form larger droplets
Q50. For a charged colloid, increasing pH may lead to stability changes because pH affects:
- Particle color only
- Surface charge and ionization of functional groups
- Gravitational constant
- Viscosity of water drastically
Correct Answer: Surface charge and ionization of functional groups
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