General characteristics of colloidal dispersions MCQs With Answer

General characteristics of colloidal dispersions MCQs With Answer

Colloidal dispersions are vital in pharmaceutics, describing systems where particles (1–1000 nm) remain dispersed yet exhibit unique optical, electrical and kinetic behaviors. B.Pharm students should grasp particle size effects, Brownian motion, Tyndall effect, stability mechanisms (electrostatic and steric), DLVO theory, zeta potential, peptization, coagulation/flocculation, and measurement methods like DLS and ultracentrifugation. Understanding lyophilic vs lyophobic systems, role of surfactants and protective colloids, and real examples (emulsions, sols, gels, aerosols) is essential for formulation and stability assessment. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What size range typically defines colloidal particles in pharmaceutics?

• 1–1000 nm
• 1–10 µm
• 1000–5000 nm
• 10–100 µm

Correct Answer: 1–1000 nm

Q2. Which phenomenon explains why a beam of light is visible when passing through a colloidal dispersion?

• Brownian motion
• Tyndall effect
• Ostwald ripening
• Coagulation

Correct Answer: Tyndall effect

Q3. Which movement keeps small colloidal particles suspended and prevents rapid sedimentation?

• Thermophoresis
• Brownian motion
• Electrophoresis
• Osmosis

Correct Answer: Brownian motion

Q4. Lyophilic colloids are characterized by which property?

• Strong affinity between dispersed phase and dispersion medium
• No interaction with dispersion medium
• Immediate coagulation on dilution
• Inability to be stabilized by surfactants

Correct Answer: Strong affinity between dispersed phase and dispersion medium

Q5. Which type of colloidal system has liquid droplets dispersed in another liquid?

• Sol
• Gel
• Emulsion
• Aerosol

Correct Answer: Emulsion

Q6. What is the primary mechanism of steric stabilization of colloids?

• Electrostatic repulsion from surface charge
• Hydration shell formation
• Adsorbed polymer layers preventing particle approach
• Increasing ionic strength to compress double layer

Correct Answer: Adsorbed polymer layers preventing particle approach

Q7. Which term describes the potential at the slipping plane that is commonly measured to assess colloidal stability?

• Surface potential
• Peclet potential
• Zeta potential
• Contact potential

Correct Answer: Zeta potential

Q8. According to the Schulze-Hardy rule, which ion property most influences coagulation of a lyophobic sol?

• Hydration number
• Valency of the counter ion
• Ionic radius
• Polarizability

Correct Answer: Valency of the counter ion

Q9. Which analytical technique is commonly used to measure particle size distribution of colloids in formulary research?

• UV-visible spectroscopy
• Dynamic light scattering (DLS)
• Flame photometry
• Gas chromatography

Correct Answer: Dynamic light scattering (DLS)

Q10. DLVO theory combines which two primary interactions to explain colloidal stability?

• Hydrogen bonding and Van der Waals
• Electrostatic repulsion and Van der Waals attraction
• Steric hindrance and hydration repulsion
• Hydrophobic interactions and ionic bonding

Correct Answer: Electrostatic repulsion and Van der Waals attraction

Q11. Which process describes conversion of precipitate into colloidal sol by addition of suitable ions?

• Coagulation
• Peptization
• Flocculation
• Gelation

Correct Answer: Peptization

Q12. Protective colloids stabilize lyophobic sols primarily by what mechanism?

• Increasing ionic strength
• Forming a steric barrier around particles
• Neutralizing particle charge
• Promoting Ostwald ripening

Correct Answer: Forming a steric barrier around particles

Q13. Which colloidal system consists of solid particles dispersed in a liquid where particles do not settle rapidly?

• Emulsion
• Sol
• Aerosol
• Foam

Correct Answer: Sol

Q14. What is flocculation in the context of colloidal dispersions?

• Complete dissolution of particles
• Reversible aggregation into loose clusters
• Irreversible fusion into a solid mass
• Transformation into a gel network

Correct Answer: Reversible aggregation into loose clusters

Q15. Which factor does NOT typically affect colloidal stability?

• pH of the medium
• Ionic strength
• Magnetic field orientation of Earth
• Presence of surfactants

Correct Answer: Magnetic field orientation of Earth

Q16. Which term refers to phase separation in emulsions where droplets rise to form a layer at the top?

• Creaming
• Caking
• Coalescence
• Flocculation

Correct Answer: Creaming

Q17. Which measurement indicates the electric charge at the particle-solution interface responsible for electrostatic stabilization?

• Conductivity only
• Zeta potential
• Viscosity
• pH alone

Correct Answer: Zeta potential

Q18. Which colloidal category is a gas dispersed in a liquid (e.g., whipped cream)?

• Foam
• Aerosol
• Gel
• Sol

Correct Answer: Foam

Q19. Which statement best describes Ostwald ripening in colloidal systems?

• Smaller particles dissolve and redeposit onto larger ones over time
• Particles acquire charge causing electrophoresis
• Immediate coagulation due to multivalent ions
• Stabilization by adsorption of surfactants

Correct Answer: Smaller particles dissolve and redeposit onto larger ones over time

Q20. In electrophoresis experiments, what is observed when a charged colloidal particle moves under an applied electric field?

• Peptization occurs
• Electrophoretic mobility is measured
• Osmotic pressure rises significantly
• Zeta potential becomes zero instantly

Correct Answer: Electrophoretic mobility is measured

Q21. Which agent would you add to an emulsion to increase kinetic stability by forming an adsorbed protective layer?

• Strong electrolyte
• Surfactant (emulsifier)
• Hydrophobic dye
• Nonpolar solvent

Correct Answer: Surfactant (emulsifier)

Q22. What is dialysis used for in colloid science?

• Separating colloidal particles by sedimentation
• Removing small ions and molecules from a colloidal dispersion
• Measuring Brownian motion directly
• Increasing particle size by aggregation

Correct Answer: Removing small ions and molecules from a colloidal dispersion

Q23. Which is a common lyophobic colloid example in pharmaceutical formulations?

• Gelatin sol
• Metallic sols like gold sol
• Starch paste
• Peptized proteins

Correct Answer: Metallic sols like gold sol

Q24. Which process reduces the thickness of the electrical double layer and may lead to coagulation?

• Lowering ionic strength
• Adding multivalent counter ions
• Addition of polymers for steric stabilization
• Decreasing particle size

Correct Answer: Adding multivalent counter ions

Q25. What role do peptizing agents play in colloidal systems?

• Promote aggregation and settling
• Convert precipitate into colloidal sol by adsorbing on particles
• Remove water to form gels
• Increase ionic strength to destabilize sols

Correct Answer: Convert precipitate into colloidal sol by adsorbing on particles

Q26. Which technique separates colloidal particles based on sedimentation rates under very high centrifugal forces?

• Ultracentrifugation
• Thin-layer chromatography
• Mass spectrometry
• Dialysis

Correct Answer: Ultracentrifugation

Q27. Which is NOT a typical optical property of colloids?

• Tyndall scattering
• Color due to particle size-dependent plasmon resonance
• Rayleigh scattering for very small particles
• Complete transparency identical to solvent always

Correct Answer: Complete transparency identical to solvent always

Q28. What is the effect of increasing temperature on Brownian motion and colloidal stability generally?

• Brownian motion decreases and stability increases
• Brownian motion increases; kinetic collisions increase which may destabilize or stabilize depending on system
• Temperature has no effect
• Particles always coagulate on heating

Correct Answer: Brownian motion increases; kinetic collisions increase which may destabilize or stabilize depending on system

Q29. Which surface-active property is essential for a molecule to act as an effective emulsifier?

• High molecular weight only
• Having both hydrophilic and hydrophobic regions (amphiphilic)
• Being completely hydrophobic
• Being an electrolyte with no hydrophobic part

Correct Answer: Having both hydrophilic and hydrophobic regions (amphiphilic)

Q30. What is coagulation value in colloid chemistry?

• Amount of coagulant required to produce rapid coagulation of a colloid
• Temperature at which colloid freezes
• Quantity of surfactant needed to stabilize a colloid
• pH at which zeta potential is maximal

Correct Answer: Amount of coagulant required to produce rapid coagulation of a colloid

Q31. Which describes a gel in pharmaceutical colloids?

• Liquid dispersed in gas
• Three-dimensional network of particles trapping liquid
• Single-phase molecular solution
• Free-flowing suspension of large crystals

Correct Answer: Three-dimensional network of particles trapping liquid

Q32. Which effect causes charged colloidal particles to attract a cloud of counter-ions near their surface?

• Steric stabilization
• Formation of electrical double layer
• DLVO repulsion only
• Hydrophobic aggregation

Correct Answer: Formation of electrical double layer

Q33. Which term refers to reversible settling where structure can be re-dispersed by gentle shaking?

• Caking
• Flocculation
• Permanent coagulation
• Ostwald ripening

Correct Answer: Flocculation

Q34. Which colloidal dispersion is characterized by solid droplets dispersed in a gas (e.g., smoke)?

• Foam
• Aerosol
• Emulsion
• Gel

Correct Answer: Aerosol

Q35. How do nonionic polymers stabilize colloids?

• By increasing ionic strength
• Through steric hindrance and hydrated layers
• By charging the particle surface intensely
• By causing immediate coagulation

Correct Answer: Through steric hindrance and hydrated layers

Q36. Which property distinguishes colloids from true solutions?

• Colloids have particles that pass through filter paper and semipermeable membranes
• Colloids show the Tyndall effect while true solutions do not
• True solutions scatter light more strongly
• Colloids have uniform molecular distribution at ionic scale

Correct Answer: Colloids show the Tyndall effect while true solutions do not

Q37. What is coacervation in colloid science?

• Formation of a dilute sol from a concentrated suspension
• Phase separation into polymer-rich and polymer-poor phases
• Permanent precipitation of colloid particles
• Evaporation-induced crystallization

Correct Answer: Phase separation into polymer-rich and polymer-poor phases

Q38. Which condition typically leads to minimal zeta potential and maximum tendency to coagulate?

• High absolute zeta potential values
• Isoelectric point or near zero zeta potential
• High steric stabilization
• Presence of strong nonionic surfactants

Correct Answer: Isoelectric point or near zero zeta potential

Q39. What role does viscosity of the continuous phase play in colloidal stability?

• Higher viscosity generally reduces particle mobility and sedimentation
• Viscosity has no effect on colloidal stability
• Lower viscosity increases steric stabilization
• Viscosity solely determines zeta potential

Correct Answer: Higher viscosity generally reduces particle mobility and sedimentation

Q40. Which is an example of a pharmaceutically important protective colloid?

• Gelatin
• Sodium chloride
• Hydrochloric acid
• Activated charcoal

Correct Answer: Gelatin

Q41. Which phenomenon describes irreversible aggregation of colloid particles into a hard mass?

• Peptization
• Caking
• Flocculation
• Brownian stabilization

Correct Answer: Caking

Q42. Which parameter is most directly altered by addition of electrolytes to a lyophobic colloid?

• Particle chemistry only
• Thickness of the electrical double layer and zeta potential
• Brownian motion speed reduction only
• Optical absorption wavelength exclusively

Correct Answer: Thickness of the electrical double layer and zeta potential

Q43. Which statement about micelles is correct in context of colloidal systems?

• Micelles form only at concentrations below the CMC
• Micelles are molecular aggregates formed above the critical micelle concentration (CMC)
• Micelles are insoluble solid colloids
• Micelle formation always causes coagulation

Correct Answer: Micelles are molecular aggregates formed above the critical micelle concentration (CMC)

Q44. What is the main driving force for adsorption of surfactants at particle surfaces?

• Maximizing system free energy
• Reduction of interfacial free energy
• Increasing total interfacial area
• Eliminating Brownian motion

Correct Answer: Reduction of interfacial free energy

Q45. Which process would most likely reverse flocculation without changing chemical composition?

• Gentle stirring or shaking to redisperse flocs
• Adding strong coagulant
• Drying the sample to powder
• Heating to very high temperature to sinter particles

Correct Answer: Gentle stirring or shaking to redisperse flocs

Q46. Which is an advantage of colloidal drug delivery systems?

• They always have infinite shelf life
• Improved bioavailability and controlled release potential
• Guaranteed absence of toxicity
• No need for sterility in parenteral use

Correct Answer: Improved bioavailability and controlled release potential

Q47. Which parameter is most important when designing nanoparticulate colloidal carriers for targeted delivery?

• Color of particles
• Particle size, surface charge, and surface functionality
• Odor of dispersion medium
• Ambient room lighting

Correct Answer: Particle size, surface charge, and surface functionality

Q48. Which phenomenon is indicated if a colloidal emulsion droplet merges with another to form a larger droplet?

• Ostwald ripening
• Coalescence
• Peptization
• Dialysis

Correct Answer: Coalescence

Q49. Which analytical method provides visual imaging at the nanoscale to study morphology of colloidal particles?

• Transmission electron microscopy (TEM)
• pH meter
• Optical microscope at low magnification
• Flame photometry

Correct Answer: Transmission electron microscopy (TEM)

Q50. In formulation science, why are surfactant concentration and type critical for colloidal stability?

• They control particle optical rotation only
• They influence interfacial tension, adsorption layer properties, and steric/electrostatic stabilization
• Surfactants always destabilize dispersions
• They replace the dispersed phase chemically

Correct Answer: They influence interfacial tension, adsorption layer properties, and steric/electrostatic stabilization

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com