Deflocculated suspensions MCQs With Answer

Introduction

Deflocculated suspensions MCQs with Answer provide B.Pharm students a focused way to master principles of suspension stability, particle behavior, and formulation strategies. This concise, keyword-rich guide covers deflocculated suspensions definition, differences from flocculated systems, causes of caking, role of zeta potential, Stoke’s law, sedimentation volume, wetting agents, and suspending agents. Understanding deflocculated suspensions helps optimize redispersibility, dosing accuracy, and drug bioavailability in liquid formulations. These MCQs target pharmaceutics concepts, measurement techniques, and practical troubleshooting used in laboratory and quality control settings. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What defines a deflocculated suspension?

• Particles exist as dispersed single entities with high repulsive forces
• Particles form loose aggregates that settle rapidly
• Particles form a network causing gelation
• Particles chemically react and precipitate

Correct Answer: Particles exist as dispersed single entities with high repulsive forces

Q2. Which problem is most associated with deflocculated suspensions?

• Caking and hard sediment
• Immediate phase separation into layers
• Excessive foaming
• Gel formation

Correct Answer: Caking and hard sediment

Q3. How does zeta potential influence deflocculation?

• High magnitude zeta potential increases electrostatic repulsion and promotes deflocculation
• Low magnitude zeta potential always promotes deflocculation
• Zeta potential has no effect on particle interactions
• Only steric forces, not zeta potential, control deflocculation

Correct Answer: High magnitude zeta potential increases electrostatic repulsion and promotes deflocculation

Q4. According to Stoke’s law, which change will decrease sedimentation velocity of suspended particles?

• Reducing particle radius
• Increasing density difference between particle and medium
• Decreasing viscosity of the medium
• Increasing gravitational acceleration

Correct Answer: Reducing particle radius

Q5. What does a low sedimentation volume (F) indicate in a deflocculated suspension?

• Extensive settling and compact sediment
• Ideal flocculation
• Stable gel network
• Complete solubilization

Correct Answer: Extensive settling and compact sediment

Q6. Which measurement helps quantify degree of flocculation in suspensions?

• Degree of flocculation (β)
• pKa value
• Partition coefficient
• Viscosity number

Correct Answer: Degree of flocculation (β)

Q7. Which formulation approach will most likely convert a deflocculated suspension into a flocculated one?

• Addition of a controlled amount of electrolyte to screen charges
• Further reducing particle size by milling
• Adding a high molecular weight polymer to increase steric stabilization
• Increasing pH to raise zeta potential magnitude

Correct Answer: Addition of a controlled amount of electrolyte to screen charges

Q8. Why are deflocculated suspensions often difficult to redisperse?

• Particles form tightly packed sediment with little porosity (caking)
• They form stable, porous aggregates that float
• They chemically polymerize during storage
• They have excessive gas entrapment preventing dispersion

Correct Answer: Particles form tightly packed sediment with little porosity (caking)

Q9. Which laboratory technique assesses particle size distribution important for deflocculation?

• Laser diffraction particle sizing
• Thin-layer chromatography
• Gas chromatography
• Mass spectrometry

Correct Answer: Laser diffraction particle sizing

Q10. Which surfactant action may increase deflocculation?

• Increasing particle surface charge by adsorption of ionic surfactant causing repulsion
• Bridging particles to form loose flocs
• Forming a depletion layer promoting aggregation
• Crosslinking polymeric chains around particles

Correct Answer: Increasing particle surface charge by adsorption of ionic surfactant causing repulsion

Q11. In DLVO theory, which two forces determine particle interaction relevant to deflocculation?

• Electrostatic repulsion and van der Waals attraction
• Hydrophobic forces and covalent bonding
• Hydrogen bonding and ionic pairing
• Magnetic attraction and steric hindrance

Correct Answer: Electrostatic repulsion and van der Waals attraction

Q12. Which practice can reduce caking in deflocculated suspensions?

• Incorporation of a flocculating agent to form loose aggregates
• Maximizing particle size distribution to a single large size
• Removing all electrolytes from the medium
• Storing at very high temperatures only

Correct Answer: Incorporation of a flocculating agent to form loose aggregates

Q13. Which parameter best describes ease of redispersion?

• Redispersibility index or subjective redispersion test
• Partition coefficient
• Melting point
• Thermal conductivity

Correct Answer: Redispersibility index or subjective redispersion test

Q14. How does pH affect deflocculation?

• Changes surface ionization altering zeta potential and repulsive forces
• It only affects color, not particle interactions
• pH always causes flocculation regardless of system
• pH has no impact if surfactants are present

Correct Answer: Changes surface ionization altering zeta potential and repulsive forces

Q15. Which suspending agent primarily increases viscosity to slow sedimentation?

• Xanthan gum
• Sodium chloride
• Sucrose
• Sodium lauryl sulfate

Correct Answer: Xanthan gum

Q16. A high degree of deflocculation typically results in which sediment morphology?

• Compact, non-porous cake
• Fluffy, porous sediment
• Viscous gel-like mass
• Systemic emulsification

Correct Answer: Compact, non-porous cake

Q17. Which ion effect is most likely to compress the electrical double layer and promote flocculation?

• Addition of multivalent cations such as Ca2+ or Al3+
• Addition of monovalent anions like Cl-
• Removal of all ions by deionization
• Addition of nonionic surfactant

Correct Answer: Addition of multivalent cations such as Ca2+ or Al3+

Q18. Which USP test is relevant for assessing suspension quality concerning sedimentation?

• Sedimentation volume and redispersion tests
• Disintegration test for tablets
• Osmolarity determination only
• Residual solvent analysis

Correct Answer: Sedimentation volume and redispersion tests

Q19. What role do wetting agents play in preparing suspensions prone to deflocculation?

• Improve particle wetting to prevent trapped air and reduce aggregation artifacts
• Cause immediate coagulation of particles
• Increase sediment density causing caking
• Neutralize drug activity

Correct Answer: Improve particle wetting to prevent trapped air and reduce aggregation artifacts

Q20. Which method reduces particle size but may increase deflocculation tendency?

• High-energy milling producing finer, highly charged particles
• Controlled flocculation with polymeric bridging
• Forming core–shell aggregates
• Spray drying into porous agglomerates

Correct Answer: High-energy milling producing finer, highly charged particles

Q21. In a deflocculated suspension, what is the expected effect on bioavailability of a poorly soluble drug?

• Variable dosing and potential reduced bioavailability due to caking
• Consistently enhanced bioavailability
• No effect because suspension form doesn’t matter
• Guaranteed faster onset of action

Correct Answer: Variable dosing and potential reduced bioavailability due to caking

Q22. Which polymeric additive provides steric stabilization and may reduce deflocculation?

• Polyvinylpyrrolidone (PVP)
• Sodium chloride
• Calcium carbonate
• Magnesium sulfate

Correct Answer: Polyvinylpyrrolidone (PVP)

Q23. Which storage condition can worsen deflocculation-related caking?

• Prolonged storage at low temperature causing tight packing
• Storage under gentle agitation
• Storage in an amber glass bottle at controlled temperature
• Storage with adequate headspace and agitation before use

Correct Answer: Prolonged storage at low temperature causing tight packing

Q24. Which instrument directly measures zeta potential to evaluate deflocculation risk?

• Electrophoretic light scattering (zeta sizer)
• UV-Vis spectrophotometer
• pH meter
• Refractometer

Correct Answer: Electrophoretic light scattering (zeta sizer)

Q25. Degree of flocculation (β) is defined as:

• Ratio of sedimentation volume of flocculated suspension to that of deflocculated suspension
• Difference in pH between suspension and solvent
• Mass fraction of drug in suspension
• Viscosity ratio at two shear rates

Correct Answer: Ratio of sedimentation volume of flocculated suspension to that of deflocculated suspension

Q26. Which is a sign that a suspension is flocculated rather than deflocculated?

• High sedimentation volume with loose, easily redispersible sediment
• Very low sedimentation volume and hard cake
• Complete dissolution of particles
• Formation of an oily layer

Correct Answer: High sedimentation volume with loose, easily redispersible sediment

Q27. Which excipient could be used as a flocculating agent to counter deflocculation?

• Electrolytes like potassium chloride at controlled concentration
• Excessive nonionic surfactant
• Highly hydrophobic oils
• Strong oxidizing agents

Correct Answer: Electrolytes like potassium chloride at controlled concentration

Q28. How does particle porosity affect sediment compaction in deflocculated suspensions?

• Low porosity leads to dense, compacted sediment (caking)
• Low porosity always increases redispersibility
• Higher porosity always causes immediate floating
• Porosity has no effect on sediment structure

Correct Answer: Low porosity leads to dense, compacted sediment (caking)

Q29. Which test assesses the rate of sedimentation relevant to deflocculated systems?

• Plotting sediment height versus time to calculate sedimentation rate
• Measure melting point of the drug
• Microbial limit test
• Determination of refractive index

Correct Answer: Plotting sediment height versus time to calculate sedimentation rate

Q30. Which factor decreases electrical double layer thickness and can lead to flocculation instead of deflocculation?

• Increasing ionic strength of the medium
• Reducing ionic strength by dilution
• Adding nonionic polymers for steric stabilization
• Decreasing temperature slightly

Correct Answer: Increasing ionic strength of the medium

Q31. Which surface characteristic commonly causes deflocculation in inorganic drug particles?

• High surface charge and low surface energy leading to strong repulsion
• Hydrophobic surfaces causing aggregation
• Surface melting points below storage temperature
• High magnetic susceptibility

Correct Answer: High surface charge and low surface energy leading to strong repulsion

Q32. Which processing step could inadvertently increase deflocculation by increasing surface charge?

• High-energy homogenization creating fresh charged surfaces
• Adding a bridging polymer during mixing
• Controlled addition of flocculant
• Using low-shear gentle mixing

Correct Answer: High-energy homogenization creating fresh charged surfaces

Q33. Which rheological property helps stabilize deflocculated suspensions against rapid sedimentation?

• Higher viscosity or pseudoplastic behavior from suspending agents
• Lower viscosity Newtonian fluid
• High elasticity without viscosity change
• Gas-phase viscosity increase

Correct Answer: Higher viscosity or pseudoplastic behavior from suspending agents

Q34. Which is a disadvantage of converting a deflocculated system to a flocculated one?

• Possible changes in appearance and potential dose uniformity if poorly controlled
• Total elimination of sedimentation issues always
• Guaranteed decrease in viscosity
• Complete prevention of microbial growth

Correct Answer: Possible changes in appearance and potential dose uniformity if poorly controlled

Q35. Which pharmaceutical example commonly shows deflocculated behavior if not properly formulated?

• Suspensions of poorly wettable powders like some antibiotics
• Stable oil-in-water creams
• Effervescent tablets
• Enteric-coated pellets in capsules

Correct Answer: Suspensions of poorly wettable powders like some antibiotics

Q36. What is the expected effect of adding a nonionic polymeric thickener to a deflocculated suspension?

• Increase in viscosity, reducing sedimentation rate and improving redispersibility
• Immediate precipitation due to ionic interactions
• Complete solubilization of solid drug
• Conversion to an emulsion

Correct Answer: Increase in viscosity, reducing sedimentation rate and improving redispersibility

Q37. Why is control of electrolyte concentration important in suspensions?

• Electrolytes screen surface charge and can convert deflocculated to flocculated state
• Electrolytes always improve solubility only
• Electrolytes only affect taste, not stability
• Electrolytes transform suspensions into gels

Correct Answer: Electrolytes screen surface charge and can convert deflocculated to flocculated state

Q38. Which analytical observation indicates stronger repulsive forces characteristic of deflocculated suspensions?

• High magnitude zeta potential (either highly positive or highly negative)
• Zero zeta potential only
• Very low particle surface area
• High level of bound water only

Correct Answer: High magnitude zeta potential (either highly positive or highly negative)

Q39. Which surface treatment can reduce deflocculation by reducing surface charge?

• Adsorption of counter-ions or use of flocculating polymer that neutralizes charge
• Increasing ionic strength without control
• Dry heating to oxidize surfaces
• Excessive sonication to raise charge

Correct Answer: Adsorption of counter-ions or use of flocculating polymer that neutralizes charge

Q40. Which property of sediment is assessed by measuring sediment porosity?

• Ability of sediment to trap liquid and resist caking
• Drug potency decline
• Evaporation rate of solvent
• Color stability

Correct Answer: Ability of sediment to trap liquid and resist caking

Q41. Which effect does temperature cycling often have on deflocculated suspensions?

• Promotes irreversible caking and changes in sediment structure
• Consistently improves redispersibility
• Removes all microbial contaminants
• Eliminates the need for suspending agents

Correct Answer: Promotes irreversible caking and changes in sediment structure

Q42. Which formulation parameter should be optimized to minimize deflocculation risk while maintaining dose uniformity?

• Particle size distribution and choice/level of suspending and flocculating agents
• Color additives only
• Container cap type exclusively
• Evaporation rate of the medium

Correct Answer: Particle size distribution and choice/level of suspending and flocculating agents

Q43. Which microscopic observation indicates deflocculated particles?

• Discrete, well-separated particles with minimal aggregation
• Large visible flocs bridged by polymer
• Networked gel matrix entrapping particles
• Homogeneous dissolved phase

Correct Answer: Discrete, well-separated particles with minimal aggregation

Q44. Which practice during manufacturing reduces air entrapment that can mislead flocculation assessment?

• Proper wetting of powder with wetting agents and degassing
• Vigorous high-speed mixing without wetting
• Rapid freeze-thaw cycles
• Adding dry powder on top without pre-wetting

Correct Answer: Proper wetting of powder with wetting agents and degassing

Q45. Which is a likely effect of adding a high concentration of nonionic surfactant to a deflocculated suspension?

• Steric stabilization that may further prevent flocculation and increase deflocculation
• Instant coagulation forming a solid mass
• Complete chemical reaction with the drug
• Reduction of solvent viscosity only

Correct Answer: Steric stabilization that may further prevent flocculation and increase deflocculation

Q46. Which concept explains why smaller, highly charged particles remain deflocculated?

• High surface area-to-charge ratio leads to strong electrostatic repulsion
• Small particles always aggregate due to gravity
• Small particles have no surface charge
• Only chemical bonding controls aggregation

Correct Answer: High surface area-to-charge ratio leads to strong electrostatic repulsion

Q47. Which design consideration helps a pharmaceutical container mitigate problems from deflocculated suspensions?

• Wide-mouth bottle allowing easy manual shaking and complete redispersion
• Completely sealed vial without headspace
• Opaque packaging only for light protection
• Rigid narrow dropper that prevents shaking

Correct Answer: Wide-mouth bottle allowing easy manual shaking and complete redispersion

Q48. Which quality control parameter monitors changes due to deflocculation during stability studies?

• Sedimentation volume, redispersibility, and particle size analysis over time
• Only assay of active ingredient irrespective of physical changes
• Only microbial limit test
• Only pH measurement without physical assessment

Correct Answer: Sedimentation volume, redispersibility, and particle size analysis over time

Q49. During formulation, what is an advantage of controlled flocculation compared to deflocculated systems?

• Improved redispersibility and reduced caking while maintaining acceptable sedimentation
• Complete elimination of sediment so dosing is unaffected
• Guaranteed chemical stabilization of the drug
• Lowering the need for preservatives

Correct Answer: Improved redispersibility and reduced caking while maintaining acceptable sedimentation

Q50. Which theoretical approach helps predict stability of deflocculated suspensions in formulation design?

• DLVO theory combined with rheological and steric stabilization considerations
• Henderson-Hasselbalch equation only
• Noyes-Whitney equation only
• Arrhenius equation for thermal degradation only

Correct Answer: DLVO theory combined with rheological and steric stabilization considerations

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.

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