Peptization MCQs With Answer

Peptization MCQs With Answer offers B. Pharm students a focused, exam-oriented review of peptization and colloidal stability in pharmaceutics. This concise introduction and question set covers core concepts such as peptization mechanism, peptizing agents, electrostatic and steric stabilization, DLVO theory, zeta potential, critical coagulation concentration, and practical implications for suspensions, emulsions, and parenteral formulations. Each MCQ emphasizes applied understanding—how electrolytes, pH, solvent polarity, and adsorbed layers affect re-dispersion and stability—helping you master both theory and formulation practice. Clear answers and varied difficulty make this ideal for revision and self-assessment. ‘Now let’s test your knowledge with 50 MCQs on this topic.’

Q1. What is peptization?

• The irreversible aggregation of colloidal particles into a gel
• The conversion of a precipitate into a colloidal sol by the addition of a peptizing agent
• The chemical decomposition of a drug molecule in solution
• The formation of micelles from surfactant monomers

Correct Answer: The conversion of a precipitate into a colloidal sol by the addition of a peptizing agent

Q2. Which of the following best describes a peptizing agent?

• A substance that neutralizes zeta potential to induce coagulation
• An electrolyte or surfactant that adsorbs on particles and promotes re-dispersion
• A polymer that causes irreversible flocculation
• A cosolvent that evaporates during drying

Correct Answer: An electrolyte or surfactant that adsorbs on particles and promotes re-dispersion

Q3. According to DLVO theory, which two forces determine colloidal stability?

• Hydrogen bonding and covalent bonding
• Van der Waals attraction and electrical double-layer repulsion
• Steric hindrance and entropy-driven attraction
• Hydrophobic forces and chelation

Correct Answer: Van der Waals attraction and electrical double-layer repulsion

Q4. An increase in ionic strength of the medium typically causes:

• An increase in double-layer thickness and enhanced stability
• A decrease in double-layer thickness and promotion of coagulation
• No change in colloidal interactions
• Disruption of van der Waals forces only

Correct Answer: A decrease in double-layer thickness and promotion of coagulation

Q5. The Schulze-Hardy rule relates to:

• The effect of temperature on solubility
• The relative effectiveness of counter-ions in causing coagulation based on valence
• The rate of peptization at different pH values
• The partitioning of drugs between phases

Correct Answer: The relative effectiveness of counter-ions in causing coagulation based on valence

Q6. Zeta potential is most directly a measure of:

• The chemical composition of particle cores
• The electrical potential at the slipping plane related to particle charge
• The molecular weight of adsorbed polymers
• The ionic mobility in bulk solution

Correct Answer: The electrical potential at the slipping plane related to particle charge

Q7. Which of the following typically acts as a steric stabilizer rather than an electrostatic peptizer?

• Sodium chloride
• Polyvinylpyrrolidone (PVP)
• Calcium chloride
• Sodium lauryl sulfate at high ionic strength

Correct Answer: Polyvinylpyrrolidone (PVP)

Q8. Critical coagulation concentration (CCC) refers to:

• The minimum concentration of peptizing agent needed to redisperse a precipitate
• The concentration of electrolyte required to cause rapid coagulation of a colloid
• The amount of surfactant necessary to form micelles
• The drug concentration that precipitates in vivo

Correct Answer: The concentration of electrolyte required to cause rapid coagulation of a colloid

Q9. Which factor increases the tendency for peptization of a flocculated suspension?

• Addition of multivalent counter-ions
• Adsorption of small amounts of oppositely charged ions that restore surface charge
• Lowering temperature drastically
• Removing all adsorbed surfactant

Correct Answer: Adsorption of small amounts of oppositely charged ions that restore surface charge

Q10. Peptization is most relevant to which pharmaceutical dosage form?

• Tablets by direct compression only
• Suspensions and some emulsions where particle dispersion is critical
• Transdermal patches exclusively
• Lyophilized powders for inhalation only

Correct Answer: Suspensions and some emulsions where particle dispersion is critical

Q11. Which analytical method is commonly used to monitor particle size changes during peptization?

• Infrared spectroscopy
• Dynamic light scattering (DLS)
• Thin-layer chromatography
• Gas chromatography

Correct Answer: Dynamic light scattering (DLS)

Q12. A negatively charged colloidal particle will be re-dispersed by adsorption of:

• Multivalent anions
• Multivalent cations that reverse or screen surface charge
• Neutral cosolvents only
• Non-ionic polymers with no adsorption

Correct Answer: Multivalent cations that reverse or screen surface charge

Q13. Which surfactant class can act both as peptizing agent and emulsifier?

• Non-ionic surfactants (e.g., Tween 80)
• Pure salts of heavy metals
• Strong oxidizing agents
• Hydrophobic oils with no headgroup

Correct Answer: Non-ionic surfactants (e.g., Tween 80)

Q14. Steric stabilization occurs primarily by:

• Electrostatic double-layer repulsion
• Adsorbed polymer layers preventing close approach of particles
• Formation of covalent bonds between particles
• Increasing ionic strength to compress double layers

Correct Answer: Adsorbed polymer layers preventing close approach of particles

Q15. Which pH condition would most likely cause peptization of a metal hydroxide precipitate?

• Adjusting pH to a value where surface charge becomes significant and soluble ions adsorb
• Maintaining pH at the point of zero charge to maximize aggregation
• Reducing pH to absolute zero
• Keeping pH constant with no ionic change

Correct Answer: Adjusting pH to a value where surface charge becomes significant and soluble ions adsorb

Q16. In peptization, adsorption of ions leads to:

• Decreased surface charge and immediate irreversible gelation
• Restoration or increase of surface charge causing electrostatic repulsion and redispersion
• Covalent modification of the particle core
• Complete elimination of van der Waals forces

Correct Answer: Restoration or increase of surface charge causing electrostatic repulsion and redispersion

Q17. Which electrolyte would have the strongest coagulating power according to valence effect?

• Na+ (monovalent)
• Ca2+ (divalent)
• Al3+ (trivalent)
• Cl- (monovalent anion)

Correct Answer: Al3+ (trivalent)

Q18. The practical importance of peptization in parenteral suspensions includes:

• Ensuring irreversible aggregation before injection
• Restoring uniform dispersion to ensure dose accuracy and reduce embolic risk
• Increasing particulate size to visible clumps
• Promoting chemical degradation of the drug

Correct Answer: Restoring uniform dispersion to ensure dose accuracy and reduce embolic risk

Q19. Which statement differentiates peptization from flocculation?

• Peptization forms loose aggregates while flocculation always produces sols
• Peptization refers to re-dispersion of aggregates into primary particles; flocculation refers to reversible aggregation into loose flocs
• They are identical processes with different names
• Flocculation is irreversible and peptization is always chemical decomposition

Correct Answer: Peptization refers to re-dispersion of aggregates into primary particles; flocculation refers to reversible aggregation into loose flocs

Q20. Which parameter directly increases when a hydrophilic polymer adsorbs on particle surfaces to stabilize colloids?

• Effective van der Waals attraction
• Steric barrier thickness and repulsion
• Ionic strength of the medium
• Rate of irreversible coagulation

Correct Answer: Steric barrier thickness and repulsion

Q21. A high magnitude (positive or negative) zeta potential typically indicates:

• Low colloidal stability
• High colloidal stability due to strong electrostatic repulsion
• Immediate precipitation
• No electrical double layer present

Correct Answer: High colloidal stability due to strong electrostatic repulsion

Q22. Which method can be used to intentionally peptize a precipitate in the lab?

• Add a suitable peptizing ion or surfactant and apply mild agitation
• Heat the precipitate above its decomposition temperature only
• Remove all solvent and dry to constant weight
• Add a strong oxidizing agent

Correct Answer: Add a suitable peptizing ion or surfactant and apply mild agitation

Q23. The role of solvent polarity in peptization is to:

• Determine the van der Waals attraction exclusively
• Affect solvation of ions and adsorption behavior of peptizing agents
• Eliminate the electrical double layer in all cases
• Fix the pH of the dispersion permanently

Correct Answer: Affect solvation of ions and adsorption behavior of peptizing agents

Q24. Which of the following is NOT typically a peptizing agent?

• Sodium citrate
• Acetic acid
• Iron filings
• Sodium dodecyl sulfate (SDS)

Correct Answer: Iron filings

Q25. Reversible aggregation where primary particles can be re-dispersed by gentle shaking is called:

• Irreversible coagulation
• Flocculation
• Ostwald ripening
• Covalent cross-linking

Correct Answer: Flocculation

Q26. Ostwald ripening in colloids refers to:

• Growth of larger particles at the expense of smaller ones due to solubility differences
• Immediate redispersion by peptizing agents
• Formation of uniform nanosized particles
• Charge neutralization induced flocculation only

Correct Answer: Growth of larger particles at the expense of smaller ones due to solubility differences

Q27. Which measurement provides direct evidence of surface charge changes during peptization?

• Viscosity measurement
• Zeta potential measurement
• Melting point determination
• Optical rotation

Correct Answer: Zeta potential measurement

Q28. Non-ionic surfactants stabilize colloids mainly by:

• Electrostatic repulsion due to high charge density
• Steric hindrance from hydrated chains preventing close approach
• Increasing ionic strength to compress double layers
• Oxidizing particle surfaces

Correct Answer: Steric hindrance from hydrated chains preventing close approach

Q29. Which is an example of a peptizing anion for metal hydroxide precipitates?

• Chloride ions that strongly cause coagulation only
• Citrate ions that complex and help re-disperse
• Solid paraffin wax
• Elemental sulfur powder

Correct Answer: Citrate ions that complex and help re-disperse

Q30. The initial step in peptization of a precipitate often involves:

• Formation of covalent bonds between particles
• Adsorption of ions or molecules that change surface potential
• Complete dehydration of particle surfaces
• Combustion of the solid phase

Correct Answer: Adsorption of ions or molecules that change surface potential

Q31. Which factor makes electrostatic stabilization less effective?

• Low ionic strength
• High dielectric constant solvent
• High concentration of multivalent counter-ions
• Large absolute zeta potential

Correct Answer: High concentration of multivalent counter-ions

Q32. Peptization can be monitored kinetically by observing:

• Changes in particle concentration by spectrophotometry or scattering intensity over time
• Changes in melting point
• Color change due to oxidation alone
• Increase in solute vapor pressure

Correct Answer: Changes in particle concentration by spectrophotometry or scattering intensity over time

Q33. Which of the following is true about adsorption layers that provide steric stabilization?

• They are thin rigid layers that promote aggregation
• They are hydrated flexible chains that resist compression and entropic loss when particles approach
• They always carry high electrical charge
• They dissolve particles completely

Correct Answer: They are hydrated flexible chains that resist compression and entropic loss when particles approach

Q34. A formulation scientist wants to prevent peptization by minimizing adsorption of oppositely charged ions. Which strategy is appropriate?

• Incorporate a protective non-ionic polymer layer to provide steric stabilization
• Increase multivalent counter-ion concentration
• Remove all surfactants and polymers
• Add strong acids to neutralize all charges

Correct Answer: Incorporate a protective non-ionic polymer layer to provide steric stabilization

Q35. Which experimental change is most likely to cause peptization of a salt-induced precipitate?

• Addition of a complexing ligand that solubilizes ions
• Removing all water by lyophilization
• Adding more precipitating salt
• Heating to inorganic decomposition temperatures

Correct Answer: Addition of a complexing ligand that solubilizes ions

Q36. Which is an example of electrostatic peptization?

• Adsorption of polyethylene glycol (PEG) to provide steric hindrance
• Adsorption of counter-ions that restore particle charge and cause repulsion
• Heating a suspension to evaporate solvent
• Mechanical milling without chemical change

Correct Answer: Adsorption of counter-ions that restore particle charge and cause repulsion

Q37. The effect of temperature on peptization is generally:

• Always negligible for colloidal stability
• Complex; it affects solubility, dynamics of adsorption, and viscosity which influence peptization kinetics
• Only lowers zeta potential linearly
• Causes immediate chemical reaction in all cases

Correct Answer: Complex; it affects solubility, dynamics of adsorption, and viscosity which influence peptization kinetics

Q38. In pharmaceutical suspensions, controlled peptization is sometimes used to:

• Create extremely large aggregates to settle rapidly
• Obtain uniform primary particle dispersion for consistent bioavailability
• Promote irreversible chemical degradation
• Remove active ingredient entirely

Correct Answer: Obtain uniform primary particle dispersion for consistent bioavailability

Q39. Which ionic condition is most likely to reverse electrostatic stabilization and induce coagulation?

• Low concentration of monovalent ions
• High concentration of trivalent counter-ions
• Adding non-adsorbing neutral polymers
• Decreasing particle core density

Correct Answer: High concentration of trivalent counter-ions

Q40. Which statement about DLVO energy barrier is correct?

• A higher energy barrier promotes particle aggregation
• A higher energy barrier prevents close approach and hence stabilizes the colloid
• DLVO theory ignores van der Waals forces entirely
• Energy barrier is unaffected by ionic strength

Correct Answer: A higher energy barrier prevents close approach and hence stabilizes the colloid

Q41. Which pharmaceutical excipient commonly used as a peptizing/stabilizing agent is a chelator that also complexes metal ions?

• Sorbitol
• Sodium citrate
• Magnesium stearate
• Paraffin oil

Correct Answer: Sodium citrate

Q42. When designing a nano-suspension, why is controlling peptization important?

• To ensure particles remain aggregated for longer shelf life
• To maintain nanoscale dispersion, prevent growth by aggregation, and ensure reproducible delivery and stability
• To make the formulation opaque for visual appeal
• To intentionally increase crystal size for filtration

Correct Answer: To maintain nanoscale dispersion, prevent growth by aggregation, and ensure reproducible delivery and stability

Q43. What is the likely effect of adding a high concentration of a non-adsorbing polymer to a colloidal dispersion?

• Induce depletion flocculation by osmotic pressure differences
• Cause immediate peptization by increasing surface charge
• Have no effect at all
• Convert all particles into micelles

Correct Answer: Induce depletion flocculation by osmotic pressure differences

Q44. Which parameter would you monitor to confirm successful peptization during formulation development?

• Viscosity only, irrespective of particle size
• Particle size distribution and zeta potential
• Boiling point of the dispersion
• Mass loss on drying only

Correct Answer: Particle size distribution and zeta potential

Q45. A negative zeta potential becomes less negative after adding salt—this indicates:

• Increased electrostatic repulsion
• Compression of the electrical double layer and reduced stability
• Formation of new chemical bonds on the particle core
• Conversion to steric stabilization automatically

Correct Answer: Compression of the electrical double layer and reduced stability

Q46. Which of the following best describes irreversible coagulation?

• Particles form loose flocs that can be redispersed by gentle shaking
• Primary particles form strong bonds (e.g., sintering or irreversible aggregation) that cannot be easily redispersed
• Particles remain perfectly stable without any interaction
• It is the same as peptization

Correct Answer: Primary particles form strong bonds (e.g., sintering or irreversible aggregation) that cannot be easily redispersed

Q47. The presence of adsorbed surfactant increases repulsion by:

• Only increasing van der Waals attraction
• Providing steric and sometimes electrostatic barriers depending on surfactant type
• Neutralizing all charges instantaneously
• Exploding particle surfaces

Correct Answer: Providing steric and sometimes electrostatic barriers depending on surfactant type

Q48. Which of the following is a potential drawback of peptization in a drug suspension?

• Improved dose uniformity always
• Unintended release of adsorbed impurities or increased chemical reactivity due to increased surface area
• Complete chemical inertness
• Permanent elimination of dissolution issues

Correct Answer: Unintended release of adsorbed impurities or increased chemical reactivity due to increased surface area

Q49. Which experimental condition would favor peptization via electrostatic mechanisms?

• Removal of all mobile ions from the medium
• Controlled addition of counter-ions that restore surface charge without causing overwhelming screening
• Adding large amounts of multivalent salts immediately
• Heating to decompose the particle surface

Correct Answer: Controlled addition of counter-ions that restore surface charge without causing overwhelming screening

Q50. In formulation troubleshooting, if a precipitate redisperses after addition of a preservative, this suggests the preservative:

• Acted as a peptizing agent by adsorbing on particle surfaces or changing ionic environment
• Degraded the API making it insoluble
• Always increases aggregation permanently
• Has no interaction with colloidal surfaces

Correct Answer: Acted as a peptizing agent by adsorbing on particle surfaces or changing ionic environment

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