Protective action of colloids MCQs With Answer

Protective action of colloids is a crucial topic for B.Pharm students exploring how colloidal stabilizers prevent aggregation, sedimentation, and loss of therapeutic activity in suspensions, emulsions, and nanoparticle drug carriers. This introduction covers mechanisms such as steric stabilization, electrostatic repulsion, hydration layers, and DLVO theory, plus practical implications for formulation design, excipient selection (e.g., PVP, gelatin, gum acacia), and stability testing. Understanding protective colloids helps optimize bioavailability, shelf life, and safety of parenteral and oral dispersions, and informs strategies for lyophilization, surface modification, and reducing protein adsorption. ‘Now let’s test your knowledge with 50 MCQs on this topic.’

Q1. What is the primary mechanism by which a protective colloid prevents aggregation of dispersed particles?

• Increasing ionic strength to compress the double layer
• Providing steric hindrance and forming a hydrated layer on particle surfaces
• Raising temperature to increase Brownian motion
• Inducing chemical cross-linking between particles

Correct Answer: Providing steric hindrance and forming a hydrated layer on particle surfaces

Q2. Which theory explains the balance between van der Waals attraction and electrostatic repulsion in colloidal stability?

• Langmuir adsorption isotherm
• DLVO theory
• Henderson-Hasselbalch equation
• Flory-Huggins theory

Correct Answer: DLVO theory

Q3. Zeta potential is most closely associated with which aspect of colloidal protective action?

• Hydrophobic hydration layer thickness
• Magnitude of electrostatic repulsion between particles
• Rate of chemical degradation of drug molecules
• Viscosity of the continuous phase

Correct Answer: Magnitude of electrostatic repulsion between particles

Q4. Which polymer is commonly used as a protective colloid in parenteral formulations to stabilize proteins?

• Polyvinylpyrrolidone (PVP)
• Sodium chloride
• Ethyl alcohol
• Magnesium stearate

Correct Answer: Polyvinylpyrrolidone (PVP)

Q5. Steric stabilization is most effective when the protective colloid forms:

• Thin, rigid ionic layers that allow close approach of particles
• Thick, flexible polymer chains extending into the medium
• Cross-linked networks between particles
• Crystalline coatings that reduce solubility

Correct Answer: Thick, flexible polymer chains extending into the medium

Q6. Which measurement technique assesses surface charge related to protective action?

• High-performance liquid chromatography (HPLC)
• Zeta potential analysis
• UV-Vis spectrophotometry for lambda max
• Gram staining

Correct Answer: Zeta potential analysis

Q7. The Schulze-Hardy rule relates colloidal stability to which factor?

• Concentration of nonionic surfactant
• Valency of counter-ions in the electrolyte
• Molecular weight of polymeric colloid
• Temperature dependence of viscosity

Correct Answer: Valency of counter-ions in the electrolyte

Q8. In protective colloid action, peptization refers to:

• Conversion of precipitate into colloidal sol by addition of protective agent
• Formation of a crystalline precipitate from solution
• Chemical degradation of colloid by hydrolysis
• Cross-linking of polymer chains to form gels

Correct Answer: Conversion of precipitate into colloidal sol by addition of protective agent

Q9. Which of the following excipients acts as a protective colloid by adsorption and steric stabilization in emulsions?

• Gum acacia
• Sodium sulfate
• Calcium carbonate
• Ethylene glycol

Correct Answer: Gum acacia

Q10. How does increasing ionic strength typically affect an electrostatically stabilized colloid?

• Increases steric barrier thickness
• Compresses the electrical double layer and promotes aggregation
• Enhances polymer adsorption onto particles
• Makes the colloid more resistant to shearing

Correct Answer: Compresses the electrical double layer and promotes aggregation

Q11. Which protective mechanism reduces protein adsorption onto particle surfaces by creating a hydration shell?

• Electrostatic destabilization
• Hydrophilic polymer adsorption (hydration layer)
• Thermal denaturation of proteins
• Ionic precipitation of proteins

Correct Answer: Hydrophilic polymer adsorption (hydration layer)

Q12. Which colloid type is typically used to protect nanoparticles during freeze-drying (lyophilization)?

• Cryoprotectant sugars such as trehalose or sucrose
• Strong acids to lower pH
• Heavy metal salts
• Nonvolatile oils

Correct Answer: Cryoprotectant sugars such as trehalose or sucrose

Q13. Electrosteric stabilization combines which two protective effects?

• Magnetic alignment and electroplating
• Electrostatic repulsion and steric hindrance from polymers
• Heat-induced viscosity increase and chemical bonding
• UV protection and enzymatic degradation

Correct Answer: Electrostatic repulsion and steric hindrance from polymers

Q14. Which parameter is most important for selecting a protective colloid for protein therapeutics?

• Ability to denature the protein at low concentration
• Biocompatibility and non-interference with biological activity
• High ionic strength to precipitate proteins
• Strong oxidative potential

Correct Answer: Biocompatibility and non-interference with biological activity

Q15. Which of the following is NOT a role of protective colloids in pharmaceutical suspensions?

• Preventing particle aggregation
• Enhancing sedimentation rate intentionally
• Improving redispersibility after storage
• Reducing interfacial tension between phases

Correct Answer: Enhancing sedimentation rate intentionally

Q16. The Gibbs adsorption equation relates surface tension changes to:

• Concentration of solute at the bulk only
• Amount of substance adsorbed at the interface
• Rate of temperature change
• Particle density in the dispersion

Correct Answer: Amount of substance adsorbed at the interface

Q17. Which protective colloid is commonly used to stabilize oral suspensions of insoluble drugs?

• Carboxymethyl cellulose (CMC)
• Concentrated hydrochloric acid
• Mercury salts
• Polyethyleneimine (highly cationic)

Correct Answer: Carboxymethyl cellulose (CMC)

Q18. What is the effect of nonionic polymers as protective colloids on temperature sensitivity?

• They always increase stability at higher temperature
• They may show temperature-dependent solubility leading to cononsolvency or phase separation
• They become ionic at high temperature
• They decompose at room temperature

Correct Answer: They may show temperature-dependent solubility leading to cononsolvency or phase separation

Q19. Which phenomenon describes the increase in average droplet size over time due to diffusion of disperse-phase molecules?

• Peptization
• Ostwald ripening
• Flocculation reversal
• Coacervation

Correct Answer: Ostwald ripening

Q20. In the context of protective colloids, HLB value helps to:

• Select appropriate surfactant for oil-in-water or water-in-oil emulsions
• Measure zeta potential directly
• Determine glass transition temperature
• Quantify polymer molecular weight

Correct Answer: Select appropriate surfactant for oil-in-water or water-in-oil emulsions

Q21. A high absolute value of zeta potential (positive or negative) generally indicates:

• Low stability due to strong attraction
• High colloidal stability due to strong electrostatic repulsion
• Immediate chemical degradation
• High solubility of dispersed phase in continuous phase

Correct Answer: High colloidal stability due to strong electrostatic repulsion

Q22. Which protective colloid would you choose to stabilize a protein-based vaccine to minimize aggregation?

• High concentration sodium dodecyl sulfate (SDS)
• Nonionic polymers like PEG or sugars like trehalose
• Strong oxidizing agents
• Formaldehyde in high concentration

Correct Answer: Nonionic polymers like PEG or sugars like trehalose

Q23. Competitive adsorption of surfactants and proteins at an interface can lead to:

• Enhanced enzymatic activity of proteins
• Displacement of protective colloid and destabilization
• Permanent covalent bonding between surfactant and particle
• Formation of crystalline shells around particles

Correct Answer: Displacement of protective colloid and destabilization

Q24. Which laboratory test assesses the tendency of a suspension to settle rapidly?

• Sedimentation volume measurement
• pKa determination
• NMR spectroscopy for drug identity
• Karl Fischer titration

Correct Answer: Sedimentation volume measurement

Q25. What role do hydrophilic-lipophilic balance (HLB) surfactants play compared to protective colloids?

• Surfactants reduce interfacial tension; protective colloids mainly provide steric/electrostatic stabilization
• Surfactants always produce larger particles than protective colloids
• Protective colloids are more likely to denature proteins than surfactants
• Surfactants act only as preservatives while colloids act as solvents

Correct Answer: Surfactants reduce interfacial tension; protective colloids mainly provide steric/electrostatic stabilization

Q26. Which condition would most likely reduce the effectiveness of a protective colloid?

• Low ionic strength buffer
• Presence of multivalent counter-ions
• Use of neutral, high-molecular-weight polymer
• Maintaining pH near the protective polymer’s stable range

Correct Answer: Presence of multivalent counter-ions

Q27. The protective action of albumin as a colloid in vivo is primarily due to:

• Its enzymatic activity in the bloodstream
• Its ability to bind drugs and provide steric/electrostatic stabilization
• Acting as a surfactant to reduce surface tension of blood
• Chelating heavy metals and precipitating them

Correct Answer: Its ability to bind drugs and provide steric/electrostatic stabilization

Q28. Which of the following is an indicator of flocculated suspension rather than a deflocculated one?

• Formation of a hard cake that cannot be redispersed
• Rapid settling with easy redispersion and loose sediment
• Uniform slow settling and compact sediment
• Immediate dissolution into clear solution

Correct Answer: Rapid settling with easy redispersion and loose sediment

Q29. How does adsorption isotherm knowledge help in designing protective colloid systems?

• It determines drug melting point
• It predicts how much stabilizer will adsorb at particle surface to achieve effective coverage
• It measures radioactivity of colloids
• It calculates refractive index of the formulation

Correct Answer: It predicts how much stabilizer will adsorb at particle surface to achieve effective coverage

Q30. Which effect does temperature increase commonly have on sterically stabilized colloids composed of nonionic polymers?

• Always improves stabilization with no exceptions
• May reduce hydration leading to collapse of polymer layers and decreased stabilization
• Instantly converts polymers into ionic surfactants
• Causes irreversible chemical cross-linking that stabilizes particles

Correct Answer: May reduce hydration leading to collapse of polymer layers and decreased stabilization

Q31. What is the role of hydrophobically modified polymers in electrosteric stabilization?

• They create rigid crystalline shells around particles
• They provide anchor points on particle surface and hydrophilic chains for steric repulsion
• They significantly increase system ionic strength
• They act as oxidizing preservatives

Correct Answer: They provide anchor points on particle surface and hydrophilic chains for steric repulsion

Q32. Which measurement directly indicates the thickness of adsorbed polymer layer providing steric stabilization?

• Zeta potential measurement
• Dynamic light scattering (measuring hydrodynamic diameter)
• pH titration curve
• Refractive index only

Correct Answer: Dynamic light scattering (measuring hydrodynamic diameter)

Q33. In vaccine formulations, protective colloids can prevent loss of antigenicity by:

• Denaturing antigens to make them smaller
• Reducing interfacial stress and preventing aggregation
• Increasing ionic strength to precipitate antigens
• Performing covalent modification of antigens

Correct Answer: Reducing interfacial stress and preventing aggregation

Q34. Which colloid property is most critical for intravenous nanoparticle formulations to avoid rapid clearance?

• Large positive surface charge to bind plasma proteins
• Hydrophilic stealth coating like PEG to reduce opsonization
• High hydrophobic surface to encourage aggregation
• High density metals for sedimentation in blood

Correct Answer: Hydrophilic stealth coating like PEG to reduce opsonization

Q35. Which process can reverse coagulated precipitate back to a colloidal state using a protective colloid?

• Peptization
• Coacervation
• Gelation
• Crystallization

Correct Answer: Peptization

Q36. The primary difference between protective colloids and simple electrolytes is:

• Protective colloids are small ions while electrolytes are macromolecules
• Protective colloids adsorb at surfaces to sterically stabilize, electrolytes mainly affect double-layer thickness
• Electrolytes form permanent covalent bonds with particles
• There is no practical difference in formulation science

Correct Answer: Protective colloids adsorb at surfaces to sterically stabilize, electrolytes mainly affect double-layer thickness

Q37. Which polymer is often used to prevent aggregation of hydrophobic drug nanoparticles and improve oral bioavailability?

• Polyethylene glycol (PEG)
• Concentrated sulfuric acid
• Lead acetate
• Pure glucose only

Correct Answer: Polyethylene glycol (PEG)

Q38. Which factor is least likely to influence adsorption of a protective polymer onto particle surface?

• Polymer molecular weight
• Particle surface chemistry (hydrophobic/hydrophilic)
• pH and ionic strength of medium
• Sunlight exposure over weeks

Correct Answer: Sunlight exposure over weeks

Q39. Which colloidal stabilizer is commonly used in topical emulsions for both stabilization and viscosity modification?

• Xanthan gum
• Hydrochloric acid
• Mercuric chloride
• Calcium oxide

Correct Answer: Xanthan gum

Q40. What is coacervation and how can protective colloids influence it?

• Coacervation is crystallization of salts; protective colloids accelerate it
• Coacervation is phase separation of polymers; protective colloids can inhibit or control coacervate formation
• Coacervation is gas evolution; protective colloids trap gases
• Coacervation is polymer degradation by enzymes unaffected by colloids

Correct Answer: Coacervation is phase separation of polymers; protective colloids can inhibit or control coacervate formation

Q41. Which measurement helps detect early aggregation or size increase in colloidal drug formulations?

• Dynamic light scattering (DLS)
• Melting point determination
• Thin-layer chromatography (TLC)
• Soxhlet extraction

Correct Answer: Dynamic light scattering (DLS)

Q42. Which property of a protective colloid reduces protein-surface interactions in medical devices or implants?

• Hydrophobic tethering groups that attract proteins
• Hydrophilic, neutrally charged polymer brush layers
• High surface roughness to trap proteins
• Metallic coatings that oxidize proteins

Correct Answer: Hydrophilic, neutrally charged polymer brush layers

Q43. What is the likely effect if a protective colloid is present below its critical concentration for surface coverage?

• Optimal steric protection and maximum stability
• Incomplete coverage leading to insufficient stabilization
• Instant dissolution of dispersed phase
• Conversion into a crystalline stabilizer

Correct Answer: Incomplete coverage leading to insufficient stabilization

Q44. Which statement best describes the role of protective colloids in controlling Ostwald ripening?

• They increase solubility of disperse phase to accelerate ripening
• They reduce interfacial tension and provide barriers that slow mass transfer between droplets
• They convert droplets into gas to prevent ripening
• They cause immediate coalescence to avoid ripening

Correct Answer: They reduce interfacial tension and provide barriers that slow mass transfer between droplets

Q45. A formulation scientist observes rapid creaming in an emulsion despite using protective colloids. Which adjustment is most appropriate?

• Remove all protective colloids
• Increase continuous phase viscosity or adjust density difference
• Heat the emulsion to boiling
• Add strong oxidizers

Correct Answer: Increase continuous phase viscosity or adjust density difference

Q46. Which of the following statements about nonionic protective colloids is TRUE?

• They impart charge-based electrostatic stabilization only
• They stabilize mainly via steric and hydration effects, not charge
• They always precipitate in presence of monovalent salts
• They are highly toxic and unsuitable for pharmaceutical use

Correct Answer: They stabilize mainly via steric and hydration effects, not charge

Q47. In nanoparticle drug delivery, surface-grafted PEG reduces protein adsorption primarily by:

• Increasing hydrophobic interactions with proteins
• Creating a steric and hydrated barrier that resists protein approach
• Cross-linking proteins onto the particle
• Lowering pH locally to denature proteins

Correct Answer: Creating a steric and hydrated barrier that resists protein approach

Q48. Which excipient would you avoid when trying to maintain electrostatically stabilized colloids?

• Low concentrations of monovalent salts
• Multivalent cations like Ca2+ or Al3+
• Nonionic polymers that do not compress double layer
• Neutral sugars used as cryoprotectants

Correct Answer: Multivalent cations like Ca2+ or Al3+

Q49. Why is monitoring pH important in formulations stabilized by proteinaceous protective colloids?

• Proteins have pI values and changes in pH affect charge, conformation, and adsorption behavior
• pH has no effect on protein stability
• Only ionic strength matters, not pH
• pH exclusively determines particle density

Correct Answer: Proteins have pI values and changes in pH affect charge, conformation, and adsorption behavior

Q50. When designing a long-term stable parenteral nanosuspension, which combination is most desirable?

• High ionic strength buffer with no polymeric stabilizer
• Biocompatible steric stabilizer (e.g., PEG) plus controlled ionic strength and optimized pH
• No attention to surface chemistry or steric layers
• Use of heavy metals to increase particle weight

Correct Answer: Biocompatible steric stabilizer (e.g., PEG) plus controlled ionic strength and optimized pH

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