Flocculated suspensions MCQs With Answer

Flocculated suspensions MCQs With Answer are essential study material for B. Pharm students learning pharmaceutical suspensions. This introduction covers key concepts such as flocculation mechanisms, flocculating agents, sedimentation behavior, redispersibility, zeta potential and stability assessment. Focused on formulation and quality control, these MCQs emphasize practical aspects: how ionic strength, pH, polymers and surfactants influence flocculation, measurement techniques like sedimentation volume and zeta potential, and strategies to prevent caking while ensuring dose uniformity. Designed to boost exam readiness and formulation skills, this set aligns with curriculum needs and industrial practice. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the best description of a flocculated suspension?

• Particles form loose, reversible aggregates that settle but are easily redispersed
• Particles remain completely dispersed with no aggregation
• Particles form hard, irreversible cakes that are difficult to redisperse
• Particles dissolve completely to form a clear solution

Correct Answer: Particles form loose, reversible aggregates that settle but are easily redispersed

Q2. Which parameter is commonly used to quantify the extent of flocculation in suspensions?

• Sedimentation volume (F)
• Viscosity index (V)
• pH value
• Melting point

Correct Answer: Sedimentation volume (F)

Q3. Sedimentation volume (F) is defined as:

• Final volume of sediment divided by original total volume of suspension
• Original volume of suspension divided by final volume of sediment
• Mass of settled particles per unit volume
• Volume of supernatant after centrifugation

Correct Answer: Final volume of sediment divided by original total volume of suspension

Q4. A high magnitude zeta potential (e.g., > ±30 mV) typically indicates:

• Strong electrostatic repulsion and a stable, deflocculated system
• Immediate flocculation due to neutralization
• Strong steric bridging between particles
• Complete dissolution of particles

Correct Answer: Strong electrostatic repulsion and a stable, deflocculated system

Q5. Which mechanism involves polymer chains adsorbing onto two or more particles to link them together?

• Polymeric bridging flocculation
• Charge neutralization
• Depletion stabilization
• Ostwald ripening

Correct Answer: Polymeric bridging flocculation

Q6. Charge neutralization as a flocculation mechanism primarily involves:

• Addition of counter-ions to reduce surface charge and zeta potential
• Increasing the viscosity to slow settling
• Adsorption of long-chain polymers for steric hindrance
• Decreasing temperature to form crystals

Correct Answer: Addition of counter-ions to reduce surface charge and zeta potential

Q7. Which of the following is a characteristic advantage of a flocculated suspension in pharmaceuticals?

• Easy redispersibility and reduced risk of caking
• Maximum chemical stability of suspended drug
• Complete prevention of sedimentation
• Faster dissolution into solution

Correct Answer: Easy redispersibility and reduced risk of caking

Q8. What is the main disadvantage of a deflocculated suspension compared to a flocculated one?

• Formation of hard cake that is difficult to redisperse
• Immediate chemical degradation of drug
• Excessive foaming during shaking
• Increased microbial contamination

Correct Answer: Formation of hard cake that is difficult to redisperse

Q9. Which analytical technique directly measures the electrostatic potential near particle surfaces used to assess flocculation tendency?

• Zeta potential analysis
• Infrared spectroscopy (FTIR)
• Ultraviolet-visible spectroscopy (UV-Vis)
• Thermogravimetric analysis (TGA)

Correct Answer: Zeta potential analysis

Q10. Which excipient class is most commonly used to provide steric stabilization and prevent flocculation?

• Non-ionic polymers (e.g., methylcellulose)
• Low molecular weight salts
• Strong acids
• Volatile solvents

Correct Answer: Non-ionic polymers (e.g., methylcellulose)

Q11. Depletion flocculation occurs when:

• Non-adsorbing polymers create an osmotic imbalance that pushes particles together
• High ionic strength causes charge reversal
• Particles chemically react to form insoluble complexes
• Temperature increase causes particle dissolution

Correct Answer: Non-adsorbing polymers create an osmotic imbalance that pushes particles together

Q12. Which of the following is a commonly used electrolyte flocculating agent?

• Sodium chloride (NaCl)
• Sorbitol
• Glycerin
• Polyethylene glycol (PEG 400)

Correct Answer: Sodium chloride (NaCl)

Q13. In formulation, bentonite primarily acts as:

• A suspending agent that increases viscosity and helps prevent rapid settling
• An antibiotic preservative
• A pH indicator
• A drug solubilizer for hydrophilic drugs

Correct Answer: A suspending agent that increases viscosity and helps prevent rapid settling

Q14. Which property is most closely associated with the ease of redispersion of a suspension?

• Nature of sediment (flocculated vs caked)
• Color of suspension
• Packaging material
• Boiling point of the medium

Correct Answer: Nature of sediment (flocculated vs caked)

Q15. Which factor does NOT commonly influence flocculation in a pharmaceutical suspension?

• Color of the active ingredient
• pH of the medium
• Ionic strength of the medium
• Type and concentration of polymers or electrolytes present

Correct Answer: Color of the active ingredient

Q16. The degree of flocculation (β) is defined as:

• The ratio of sedimentation volume of flocculated suspension to that of corresponding deflocculated suspension
• The ratio of particle size before and after flocculation
• The mass fraction of solids in the sediment
• The time taken for complete settling

Correct Answer: The ratio of sedimentation volume of flocculated suspension to that of corresponding deflocculated suspension

Q17. Which of the following surfactants can act as a wetting agent to improve dispersion of hydrophobic powders in water?

• Sodium lauryl sulfate (SLS)
• Magnesium stearate
• Calcium carbonate
• Hexane

Correct Answer: Sodium lauryl sulfate (SLS)

Q18. Which rheological property is often increased to slow down sedimentation and provide physical stability?

• Viscosity
• Vapor pressure
• Electrical conductivity
• Optical density

Correct Answer: Viscosity

Q19. Which of the following tests evaluates the physical stability and redispersibility of a suspension in quality control?

• Shake and redispersion test
• Melting point determination
• Gas chromatography
• Karl Fischer titration

Correct Answer: Shake and redispersion test

Q20. Which change is most likely to promote flocculation by reducing electrostatic repulsion?

• Adding multivalent counter-ions (e.g., Ca2+ or Al3+)
• Adding non-adsorbing polymers to sterically stabilize
• Increasing the pH far from the isoelectric point
• Lowering the temperature to freeze the medium

Correct Answer: Adding multivalent counter-ions (e.g., Ca2+ or Al3+)

Q21. Which factor is critical when selecting a flocculating agent for a drug suspension?

• Compatibility with drug and excipients
• Color matching with drug
• Ability to evaporate quickly
• Flammability

Correct Answer: Compatibility with drug and excipients

Q22. Which of the following is a polymeric flocculating agent used in pharmaceutical suspensions?

• Acacia (gum arabic)
• Sodium chloride
• Hydrochloric acid
• Isopropyl alcohol

Correct Answer: Acacia (gum arabic)

Q23. According to DLVO theory, colloidal stability results from balance between which two forces?

• van der Waals attractive forces and electric double-layer repulsive forces
• Gravitational and centrifugal forces
• Hydrogen bonding and covalent bonding
• Viscosity and vapor pressure

Correct Answer: van der Waals attractive forces and electric double-layer repulsive forces

Q24. Which observation suggests that a suspension is flocculated rather than deflocculated?

• Rapid settling with loose, easily redispersible sediment
• Very slow settling with compact, irreversibly caked sediment
• Complete clarity of the dispersion medium
• Formation of gas bubbles inside the suspension

Correct Answer: Rapid settling with loose, easily redispersible sediment

Q25. To reverse unwanted flocculation, a formulator might:

• Add steric stabilizers or adjust pH/ionic strength to increase repulsion
• Increase temperature to dissolve the suspended particles
• Add more drug powder to the suspension
• Remove all water from the formulation

Correct Answer: Add steric stabilizers or adjust pH/ionic strength to increase repulsion

Q26. Which technique helps visualize floc structure and particle interactions directly?

• Optical or electron microscopy
• Infrared spectroscopy
• Nitrogen adsorption (BET) alone
• pH titration

Correct Answer: Optical or electron microscopy

Q27. In a flocculated suspension, how does particle size distribution typically compare to before flocculation?

• Effective aggregate size is larger due to loose association of primary particles
• Primary particle size becomes chemically smaller
• Particle size distribution becomes monodisperse and smaller
• All particles dissolve and disappear

Correct Answer: Effective aggregate size is larger due to loose association of primary particles

Q28. Which excipient can both act as a suspending agent and influence flocculation by adsorption?

• Bentonite clay
• Ethyl acetate
• Magnesium stearate in high amounts
• Methanol

Correct Answer: Bentonite clay

Q29. Which physical test provides quantitative data on sedimentation kinetics of suspensions?

• Monitoring sedimentation volume versus time
• Measuring color change over time
• Assessing taste by sensory panels
• Measuring melting point of sediment

Correct Answer: Monitoring sedimentation volume versus time

Q30. Which is a desired characteristic of a flocculated pharmaceutical suspension for patient use?

• Uniform dose after gentle shaking and ease of redispersion
• Formation of a hard, compact cake after storage
• Poor wetting of particles
• Immediate gas evolution on opening

Correct Answer: Uniform dose after gentle shaking and ease of redispersion

Q31. Which statement about flocculation and chemical stability is most accurate?

• Flocculation primarily affects physical stability; chemical stability must still be controlled separately
• Flocculation always increases chemical stability of the drug
• Flocculation causes immediate chemical degradation of drugs
• Physical flocculation and chemical stability are the same parameter

Correct Answer: Flocculation primarily affects physical stability; chemical stability must still be controlled separately

Q32. Which factor often needs control to maintain consistent flocculation behavior between batches?

• Ionic strength and excipient concentrations
• Ambient room color
• Time of day when manufacturing occurs
• Barcode type on packaging

Correct Answer: Ionic strength and excipient concentrations

Q33. Which commonly used polymer can provide steric stabilization and reduce flocculation when adsorbed on particle surfaces?

• Polyvinylpyrrolidone (PVP)
• Sodium chloride
• Hydrochloric acid
• Calcium carbonate

Correct Answer: Polyvinylpyrrolidone (PVP)

Q34. Which formulation approach helps to promote flocculation intentionally to avoid caking?

• Add controlled amounts of electrolyte to reduce repulsive forces and form loose flocs
• Remove all excipients so particles float freely
• Freeze-dry the suspension to eliminate water
• Add volatile organic solvents to dissolve particles

Correct Answer: Add controlled amounts of electrolyte to reduce repulsive forces and form loose flocs

Q35. Which is NOT a method to characterize flocculated suspensions?

• Measuring the boiling point of the suspension
• Sedimentation volume measurement
• Zeta potential analysis
• Microscopy to observe floc structure

Correct Answer: Measuring the boiling point of the suspension

Q36. Increasing which parameter generally increases sedimentation rate according to Stokes’ law?

• Particle size (diameter)
• Optical clarity
• pH stability range
• Color intensity

Correct Answer: Particle size (diameter)

Q37. Which statement about reversible versus irreversible aggregation is correct?

• Flocculation is typically reversible; coagulation leading to caking is often irreversible
• All aggregation is irreversible
• Reversible aggregation leads to hard cakes
• Irreversible aggregation improves redispersibility

Correct Answer: Flocculation is typically reversible; coagulation leading to caking is often irreversible

Q38. Which pH-related phenomenon can cause flocculation of protein suspensions?

• Approaching the protein isoelectric point reduces net charge causing aggregation
• Moving pH away from the isoelectric point increases flocculation
• Any pH change dissolves proteins completely
• Protein flocculation is independent of pH

Correct Answer: Approaching the protein isoelectric point reduces net charge causing aggregation

Q39. In designing a flocculated suspension, why is control of preservative distribution important?

• To ensure antimicrobial protection is present uniformly throughout the product
• Because preservatives are primary flocculating agents
• Because preservatives determine the color of sediment
• Preservatives are irrelevant in flocculated formulations

Correct Answer: To ensure antimicrobial protection is present uniformly throughout the product

Q40. Which process can lead to irreversible caking even in initially flocculated suspensions?

• Ostwald ripening and dehydration of sediment over time
• Reducing ionic strength to zero
• Mild shaking before use
• Maintaining refrigeration

Correct Answer: Ostwald ripening and dehydration of sediment over time

Q41. Steric stabilization differs from electrostatic stabilization because steric stabilization:

• Uses adsorbed polymer layers to physically prevent close particle approach
• Relies on increasing ionic strength to promote repulsion
• Reduces particle solubility to form crystals
• Only functions at extreme pH values

Correct Answer: Uses adsorbed polymer layers to physically prevent close particle approach

Q42. Which measurement would you use to monitor particle aggregation kinetics quantitatively?

• Dynamic light scattering (DLS) to track changes in hydrodynamic diameter
• Melting point apparatus
• Thin layer chromatography
• Moisture content by oven drying only

Correct Answer: Dynamic light scattering (DLS) to track changes in hydrodynamic diameter

Q43. When using a polymeric flocculant, which property of the polymer is most important for bridging?

• Chain length and ability to adsorb partially onto multiple particles
• High volatility
• High acidity
• Low molecular flexibility

Correct Answer: Chain length and ability to adsorb partially onto multiple particles

Q44. Which scenario will likely decrease the sedimentation volume F of a suspension?

• Subjecting the suspension to compression that forms a dense cake
• Adding an appropriate flocculating agent that forms loose flocs
• Increasing viscosity to slow settling
• Using steric stabilizers to maintain dispersion

Correct Answer: Subjecting the suspension to compression that forms a dense cake

Q45. Which is the most appropriate immediate action if a filled suspension batch shows irreversible caking during QC testing?

• Investigate formulation and process parameters; consider reformulation or process change
• Proceed to release without changes
• Increase storage temperature and re-test
• Label the product as non-redispersible and ship

Correct Answer: Investigate formulation and process parameters; consider reformulation or process change

Q46. Which excipient commonly improves wettability of hydrophobic drug particles to aid formation of a uniform suspension?

• Surfactants such as polysorbates
• Bulk fillers like microcrystalline cellulose used dry
• Magnesium stearate in high amounts
• Non-volatile oils only

Correct Answer: Surfactants such as polysorbates

Q47. If zeta potential magnitude decreases toward zero, what is the expected effect on particle interactions?

• Reduced electrostatic repulsion and increased likelihood of aggregation/flocculation
• Increased electrostatic repulsion and improved dispersion stability
• Immediate dissolution into solvent
• No change in particle interactions

Correct Answer: Reduced electrostatic repulsion and increased likelihood of aggregation/flocculation

Q48. Which storage condition most directly contributes to dehydration of the sediment and potential caking?

• Low humidity and increased temperature accelerating water loss
• Storing in amber glass at controlled humidity
• Refrigeration at stable temperature with sealed cap
• Short-term storage with frequent shaking

Correct Answer: Low humidity and increased temperature accelerating water loss

Q49. When evaluating a new flocculating agent, which compatibility test is essential?

• Drug-excipient compatibility studies including visual, chemical and potency assays
• Determination of agent’s melting point only
• Measuring agent’s odor intensity
• Testing ability to form foam

Correct Answer: Drug-excipient compatibility studies including visual, chemical and potency assays

Q50. Which approach is used to intentionally maintain a flocculated but uniform suspension for oral liquid dosage forms?

• Use controlled flocculant levels combined with appropriate suspending and wetting agents
• Exclude all excipients and add abrasive agents
• Allow particles to fully coagulate and form hard cakes
• Rely solely on refrigeration without formulation changes

Correct Answer: Use controlled flocculant levels combined with appropriate suspending and wetting agents

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