Classification of colloids MCQs With Answer

Classification of colloids MCQs With Answer is an essential study area for B. Pharm students focusing on colloidal systems, stability, and dosage form design. This introduction covers core concepts: types of colloids by physical state and dispersion medium, lyophilic vs lyophobic systems, particle size range, surfactant roles, Tyndall effect, Brownian motion, protective colloids, and pharmaceutical examples like emulsions, suspensions, gels and aerosols. Understanding colloid classification helps in formulation, stability testing, and predicting behavior during storage and administration. Targeted practice improves exam readiness and practical formulation skills. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the typical size range for colloidal particles?

• 0.1 nm to 1 nm
• 1 nm to 1 µm
• 1 µm to 100 µm
• 100 µm to 1 mm

Correct Answer: 1 nm to 1 µm

Q2. Which classification of colloids is based on the state of dispersed phase and dispersion medium?

• Electrical classification
• Physical state classification
• Optical classification
• Stability classification

Correct Answer: Physical state classification

Q3. Lyophilic colloids are best described as:

• Colloids with strong affinity for dispersion medium
• Colloids with no affinity for dispersion medium
• Colloids that always coagulate quickly
• Colloids composed only of metals

Correct Answer: Colloids with strong affinity for dispersion medium

Q4. Which of the following is an example of an aerosol colloid?

• Milk
• Fog
• Gelatin gel
• Suspension of talc in oil

Correct Answer: Fog

Q5. The Tyndall effect in colloids is used to demonstrate:

• Viscosity changes
• Light scattering by particles
• pH dependent solubility
• Chemical composition

Correct Answer: Light scattering by particles

Q6. Which phenomenon keeps colloidal particles suspended against gravity?

• Osmosis
• Brownian motion
• Coagulation
• Crystallization

Correct Answer: Brownian motion

Q7. A colloid that is liquid dispersed in liquid is called:

• Sol
• Gel
• Emulsion
• Aerosol

Correct Answer: Emulsion

Q8. Protective colloids are used to:

• Promote coagulation of lyophobic sols
• Stabilize lyophobic sols against coagulation
• Increase sedimentation rate
• Convert sols into aerosols

Correct Answer: Stabilize lyophobic sols against coagulation

Q9. Which is a lyophobic colloid example commonly used in pharmaceutics?

• Gelatin solution
• Hydrophilic polymer solution
• Gold sol
• Starch paste

Correct Answer: Gold sol

Q10. Emulsions are classified by the internal and external phases; which term describes oil dispersed in water?

• W/O (water-in-oil)
• O/W (oil-in-water)
• S/O (solid-in-oil)
• G/O (gas-in-oil)

Correct Answer: O/W (oil-in-water)

Q11. Which technique separates colloidal particles from excess ions across a semi-permeable membrane?

• Dialysis
• Chromatography
• Lyophilization
• Distillation

Correct Answer: Dialysis

Q12. Flocculation in suspensions refers to:

• Complete dissolution of particles
• Formation of loose aggregates reversible by shaking
• Irreversible coagulation forming compact cake
• Evaporation of solvent

Correct Answer: Formation of loose aggregates reversible by shaking

Q13. Which method is commonly used to prepare fine emulsions in pharmaceutics?

• Filtration
• High-pressure homogenization
• Recrystallization
• Cold fusion

Correct Answer: High-pressure homogenization

Q14. The DLVO theory explains stability of colloids by considering which two forces?

• Hydrogen bonding and van der Waals forces
• Electrostatic repulsion and van der Waals attraction
• Steric hindrance and covalent bonding
• Magnetic and gravitational forces

Correct Answer: Electrostatic repulsion and van der Waals attraction

Q15. Which term refers to a colloidal system where solid is dispersed in liquid?

• Emulsion
• Sol
• Aerosol
• Foam

Correct Answer: Sol

Q16. Critical micelle concentration (CMC) is important because it represents:

• The concentration where surfactant begins to precipitate
• The concentration where micelles form in solution
• The point of complete dissolution of polymers
• The temperature of colloid coagulation

Correct Answer: The concentration where micelles form in solution

Q17. Which colloid classification is based on interaction with the dispersion medium (affinity)?

• Optical classification
• Electrokinetic classification
• Lyophilicity classification
• Size-based classification

Correct Answer: Lyophilicity classification

Q18. Peptization refers to:

• Conversion of a sol into a gel
• Dispersal of coagulated material back into colloidal sol by addition of electrolyte or peptizing agent
• Removal of water by freeze-drying
• Formation of micelles from surfactants

Correct Answer: Dispersal of coagulated material back into colloidal sol by addition of electrolyte or peptizing agent

Q19. Which test indicates the presence of a colloidal dispersion by passing light?

• Beilstein test
• Tyndall effect
• Flame test
• pH titration

Correct Answer: Tyndall effect

Q20. Zeta potential is a measure of:

• Particle size distribution only
• Electrical potential at the slipping plane of particles
• Optical density of colloid
• Viscosity of dispersion medium

Correct Answer: Electrical potential at the slipping plane of particles

Q21. Which classification includes sols, gels, and emulsions based on physical appearance?

• Chemical classification
• Pharmaceutical classification
• State of aggregation classification
• Physical state classification

Correct Answer: Physical state classification

Q22. Coagulation value of an electrolyte indicates:

• The minimum concentration of electrolyte required to cause coagulation
• The pH at which colloid dissolves
• The temperature needed for coagulation
• The viscosity at which coagulation stops

Correct Answer: The minimum concentration of electrolyte required to cause coagulation

Q23. Which of the following is a characteristic of lyophilic colloids?

• Low viscosity even at high concentrations
• Readily reversible with addition of solvent and stable
• Highly sensitive to electrolytes causing rapid coagulation
• Always form gels at room temperature

Correct Answer: Readily reversible with addition of solvent and stable

Q24. Which colloidal dosage form is a semisolid with liquid dispersed in a solid network?

• Suspension
• Gel
• Emulsion
• Spray

Correct Answer: Gel

Q25. Which analytical method measures particle size distribution in colloids?

• UV-visible spectroscopy only
• Dynamic light scattering (DLS)
• Simple filtration
• pH meter

Correct Answer: Dynamic light scattering (DLS)

Q26. Steric stabilization of colloids is achieved by:

• Adding multivalent electrolytes
• Adsorbing polymers or nonionic surfactants on particle surfaces
• Increasing temperature to boiling
• Applying strong electric fields

Correct Answer: Adsorbing polymers or nonionic surfactants on particle surfaces

Q27. Which of the following is NOT a classification criterion for colloids?

• Size of dispersed phase
• Physical state of phases
• Electrical charge only
• Nature of interaction with dispersing medium

Correct Answer: Electrical charge only

Q28. Micelles are examples of which type of colloid?

• Lyophobic sols
• Association colloids
• Metallic sols
• Gels

Correct Answer: Association colloids

Q29. Which process describes the conversion of a gel into sol by mechanical action?

• Gelation
• Thixotropy
• Coacervation
• Flocculation

Correct Answer: Thixotropy

Q30. A colloid that shows Brownian motion and scattering of light is typically:

• Macroscopic precipitate
• True solution
• Colloidal dispersion
• Gaseous mixture

Correct Answer: Colloidal dispersion

Q31. Which of the following is an example of a gas dispersed in liquid colloid?

• Foam
• Emulsion
• Sol
• Solid aerosol

Correct Answer: Foam

Q32. Which electrolyte is most effective in coagulating a negatively charged colloid according to Schulze-Hardy rule?

• Monovalent cation
• Bivalent cation
• Trivalent cation
• Any anion

Correct Answer: Trivalent cation

Q33. Which pharmaceutical example best illustrates a lyophilic colloid?

• Colloidal gold
• Gelatin solution
• Silver sol
• Smokes (aerosols)

Correct Answer: Gelatin solution

Q34. Sedimentation volume (F) in suspensions is a measure of:

• Percent drug released in vitro
• Relative volume of sediment compared to total volume
• Viscosity of dispersion medium
• Particle zeta potential

Correct Answer: Relative volume of sediment compared to total volume

Q35. What is peptizing agent’s role in colloidal chemistry?

• Promote irreversible aggregation
• Disperse coagulated particles back into colloidal form
• Lower temperature of gelation
• Increase particle size permanently

Correct Answer: Disperse coagulated particles back into colloidal form

Q36. Which is true for lyophobic colloids compared to lyophilic colloids?

• Lyophobic colloids are more stable in presence of electrolytes
• Lyophobic colloids require stabilizers and are sensitive to electrolytes
• Lyophobic colloids are always biological
• Lyophobic colloids form gels readily

Correct Answer: Lyophobic colloids require stabilizers and are sensitive to electrolytes

Q37. Electrophoresis in colloid studies helps determine:

• Particle pH
• Direction and magnitude of particle charge
• Viscosity only
• Chemical composition of particles

Correct Answer: Direction and magnitude of particle charge

Q38. Which of the following is an application of colloids in drug delivery?

• Immediate release tablets only
• Liposomes and nanoparticulate suspensions for targeted delivery
• Bulk powders with no colloidal properties
• Simple aqueous solutions without particles

Correct Answer: Liposomes and nanoparticulate suspensions for targeted delivery

Q39. Coacervation is a process used in:

• Micelle destabilization only
• Microencapsulation of drugs using colloidal phase separation
• Solid state crystallization
• Measuring sedimentation rate

Correct Answer: Microencapsulation of drugs using colloidal phase separation

Q40. Which parameter increases when surfactant concentration exceeds CMC?

• Surface tension continues to decrease significantly
• Micelle formation and solubilization capacity increase
• Particle size of true solutions increases above 1 mm
• pH becomes neutral automatically

Correct Answer: Micelle formation and solubilization capacity increase

Q41. Dialysis is primarily used to remove which species from colloidal dispersions?

• Colloidal particles larger than membrane pores
• Small ions and low molecular weight solutes
• Macromolecular polymers
• Non-volatile solvents

Correct Answer: Small ions and low molecular weight solutes

Q42. Which property differentiates sols from true solutions?

• Sols do not scatter light while true solutions do
• Sols show Tyndall effect; true solutions do not
• True solutions show Brownian motion only
• Only true solutions contain particles larger than 1 µm

Correct Answer: Sols show Tyndall effect; true solutions do not

Q43. In pharmaceutical emulsions, which agent primarily reduces interfacial tension?

• Antioxidants
• Surfactants/emulsifiers
• Preservatives
• Buffer salts

Correct Answer: Surfactants/emulsifiers

Q44. Which classification refers to colloids formed by aggregation of molecules into larger assemblies like micelles?

• Association colloids
• Hydrophobic sols
• Metallic sols
• Gaseous colloids

Correct Answer: Association colloids

Q45. Which test distinguishes colloidal suspensions from coarse dispersions?

• Sedimentation under Stokes’ law only
• Observation of Tyndall effect and Brownian motion
• Color comparison alone
• pH measurement alone

Correct Answer: Observation of Tyndall effect and Brownian motion

Q46. Which process is commonly used to dry colloidal suspensions while preserving structure?

• Spray drying or lyophilization (freeze-drying)
• Simple oven drying at high temperature
• Distillation to dryness
• Crushing and sieving

Correct Answer: Spray drying or lyophilization (freeze-drying)

Q47. In classifying colloids by optical properties, which system does NOT scatter light?

• True solution
• Colloidal dispersion
• Coarse suspension
• Emulsion

Correct Answer: True solution

Q48. Which of the following increases colloidal stability by providing an electrostatic barrier?

• Addition of large amounts of electrolyte
• Generation of high zeta potential of like sign on particles
• Removing surfactants
• Heating to high temperature

Correct Answer: Generation of high zeta potential of like sign on particles

Q49. Which pharmaceutical formulation is an example of a solid-in-liquid colloid?

• Suspension of active drug particles in water
• Gasoline (single phase liquid)
• True solution cough syrup
• Compressed tablet

Correct Answer: Suspension of active drug particles in water

Q50. What role do surfactants play in classification and stabilization of colloids?

• They always cause coagulation of colloids
• They lower interfacial tension, form micelles, and provide steric/electrostatic stabilization
• They change particle chemical composition permanently
• They convert colloids into true solutions by evaporation

Correct Answer: They lower interfacial tension, form micelles, and provide 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