Suspensions – coarse dispersions MCQs With Answer

Suspensions – coarse dispersions MCQs With Answer

Suspensions are coarse dispersions of insoluble solid particles in a liquid medium and are a foundational subject for B. Pharm students studying pharmaceutics and dosage form design. Mastery of particle size, wetting, suspended-state stability, sedimentation, flocculation, rheology, Stoke’s law, zeta potential and choice of suspending agents (e.g., bentonite, cellulose derivatives) is critical for robust formulation and quality control. Practical topics include wetting agents, preservatives, buffers, levigation, homogenization and stability testing. These MCQs are crafted to deepen conceptual understanding, cover calculations, formulation strategies and regulatory considerations for exam and professional readiness. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which statement best defines a suspension in pharmaceutics?

• A homogeneous solution of drug molecules in a solvent
• A coarse dispersion where insoluble solid particles are dispersed throughout a liquid
• An emulsion of two immiscible liquids
• A gas dispersed in a liquid

Correct Answer: A coarse dispersion where insoluble solid particles are dispersed throughout a liquid

Q2. Coarse dispersions are typically characterized by which particle size range?

• Less than 1 nm
• 1–100 nm
• 0.1–10 µm
• Greater than 1 µm

Correct Answer: Greater than 1 µm

Q3. Which of the following is a common consequence of particle aggregation in suspensions?

• Increased solubility
• Reduced sedimentation rate
• Caking and difficulty in re-dispersion
• Improved bioavailability

Correct Answer: Caking and difficulty in re-dispersion

Q4. Stoke’s law is used to predict which property of suspended particles?

• Diffusion coefficient
• Sedimentation velocity
• Viscosity of suspension

Correct Answer: Sedimentation velocity

Q5. Sedimentation volume (F) is defined as:

• The ratio of height of settled solid to original suspension height
• The ratio of original suspension height to height of settled solid
• The time taken for complete sedimentation
• The volume of supernatant liquid produced

Correct Answer: The ratio of height of settled solid to original suspension height

Q6. Which parameter increases the sedimentation rate according to Stoke’s law?

• Decrease in particle density relative to medium
• Increase in particle radius
• Increase in medium viscosity
• Decrease in gravitational constant

Correct Answer: Increase in particle radius

Q7. What is flocculation in the context of suspensions?

• The formation of a hard, incompressible cake
• The reversible aggregation of particles into loose networks
• The dissolution of particles into the medium
• The chemical degradation of suspended drug

Correct Answer: The reversible aggregation of particles into loose networks

Q8. Which term describes irreversible aggregation that leads to caking?

• Flocculation
• Deflocculation
• Coagulation
• Peptization

Correct Answer: Coagulation

Q9. Which excipient is commonly used as a suspending agent to increase viscosity?

• Sodium lauryl sulfate
• Bentonite
• Sodium chloride
• Polysorbate 80 only

Correct Answer: Bentonite

Q10. Which is an example of a cellulose derivative used as a suspending agent?

• Carboxymethyl cellulose (CMC)
• Sodium chloride
• Magnesium stearate
• Ethyl oleate

Correct Answer: Carboxymethyl cellulose (CMC)

Q11. Wetting agents are added to suspensions primarily to:

• Increase pH
• Reduce surface tension and displace air from particle surfaces
• Sterilize the formulation
• Increase particle density

Correct Answer: Reduce surface tension and displace air from particle surfaces

Q12. Which of the following is a common wetting agent?

• Glycerin
• Polysorbate 80 (Tween 80)
• Magnesium hydroxide
• Calcium carbonate

Correct Answer: Polysorbate 80 (Tween 80)

Q13. Zeta potential gives information about:

• Particle size distribution
• Surface charge and electrostatic stability
• Viscosity of the medium
• pH of the suspension

Correct Answer: Surface charge and electrostatic stability

Q14. Increasing the ionic strength of the medium often causes:

• Increased electrostatic repulsion between particles
• Compression of the electrical double layer and possible flocculation
• Sterilization of particles
• Increase in zeta potential magnitude

Correct Answer: Compression of the electrical double layer and possible flocculation

Q15. A high sedimentation volume (F ≈ 1) generally indicates:

• Complete caking
• Good suspension stability
• Very high sediment compactness
• Immediate settling

Correct Answer: Good suspension stability

Q16. Which process is commonly used to reduce particle size for suspensions?

• Granulation
• Trituration and milling
• Lyophilization
• Compression

Correct Answer: Trituration and milling

Q17. Levigation is best described as:

• Dry grinding in an open mortar
• Wetting powder and grinding it to reduce particle size
• Heating particles to fuse them
• Freeze-drying a suspension

Correct Answer: Wetting powder and grinding it to reduce particle size

Q18. Which method is used to determine particle size distribution in suspensions?

• High-performance liquid chromatography
• Laser diffraction
• Titration
• UV-visible spectrophotometry only

Correct Answer: Laser diffraction

Q19. In a flocculated suspension, re-dispersibility is typically:

• Poor and impossible
• Good and easy with slight shaking
• Dependent on pH only
• Irrelevant to formulation

Correct Answer: Good and easy with slight shaking

Q20. Which property of a suspending agent most directly affects flow behavior?

• Surface tension
• Viscosity and rheological behavior
• Color
• Solubility in nonpolar solvents

Correct Answer: Viscosity and rheological behavior

Q21. Thixotropy in suspensions refers to:

• Permanent hardening on standing
• Time-dependent decrease in viscosity on shear and recovery at rest
• Increase in particle size on stirring
• pH-dependent color change

Correct Answer: Time-dependent decrease in viscosity on shear and recovery at rest

Q22. Which preservative is commonly used in aqueous suspensions?

• Phenol
• Benzoic acid derivatives like sodium benzoate
• Bentonite
• Xanthan gum

Correct Answer: Benzoic acid derivatives like sodium benzoate

Q23. Which factor can reduce preservative efficacy in suspensions?

• High solubility of drug
• Adsorption of preservative onto particles
• Using sterile water
• Low particle size only

Correct Answer: Adsorption of preservative onto particles

Q24. Which of the following is a rheology modifier derived from natural gums?

• Carbomer
• Xanthan gum
• Poloxamer
• Polyethylene glycol

Correct Answer: Xanthan gum

Q25. Which laboratory test evaluates the redispersibility of a suspension?

• pH titration
• Shake test and observation of uniformity
• HPLC assay only
• Viscosity at infinite shear

Correct Answer: Shake test and observation of uniformity

Q26. The creaming of a suspension refers to:

• Particles settling to the bottom
• Particles rising to the top forming a concentrated layer
• Complete dissolution of particles
• Formation of gas bubbles

Correct Answer: Particles rising to the top forming a concentrated layer

Q27. Which factor decreases the tendency for caking?

• Formation of a hard, compact sediment
• Flocculation producing loose aggregates
• High interparticle attraction
• Use of large, dense particles only

Correct Answer: Flocculation producing loose aggregates

Q28. In preparing suspensions, dispersion of hydrophobic powders is improved by:

• Using nonpolar solvents exclusively
• Wetting with suitable surfactants or levigating agents
• Heating to boiling temperature
• Avoiding surfactants

Correct Answer: Wetting with suitable surfactants or levigating agents

Q29. Which analytical parameter is essential for content uniformity in suspensions?

• Zeta potential only
• Assay of active ingredient by validated method
• Color measurement
• Refractive index

Correct Answer: Assay of active ingredient by validated method

Q30. What is the major concern when autoclaving suspensions?

• Increase in viscosity only
• Particle growth, aggregation, or chemical degradation of drug
• Complete sterilization with no effects
• Loss of color only

Correct Answer: Particle growth, aggregation, or chemical degradation of drug

Q31. Which of the following suspensions is intended for ocular use and requires special considerations?

• Parenteral suspension
• Topical suspension for skin
• Ophthalmic suspension
• Oral syrup

Correct Answer: Ophthalmic suspension

Q32. What is peptization?

• The formation of a gel from sol
• The conversion of a flocculated mass into a colloidal dispersion by addition of peptizing agent
• The process of sterilization by filtration
• Removal of preservatives by adsorption

Correct Answer: The conversion of a flocculated mass into a colloidal dispersion by addition of peptizing agent

Q33. Which technique is most suitable for sterilizing heat-sensitive suspensions?

• Autoclaving at 121°C
• Dry heat sterilization
• Sterile filtration of vehicle and aseptic processing
• Boiling for 5 minutes

Correct Answer: Sterile filtration of vehicle and aseptic processing

Q34. Which of the following increases suspension stability by providing steric stabilization?

• Electrolytes
• Polymers adsorbed on particle surface (e.g., PEG, PVP)
• Acidification only
• High shear mixing alone

Correct Answer: Polymers adsorbed on particle surface (e.g., PEG, PVP)

Q35. What is the primary role of buffers in suspensions?

• To increase particle size
• To maintain pH for drug stability and preservative efficacy
• To act as wetting agents
• To sterilize the formulation

Correct Answer: To maintain pH for drug stability and preservative efficacy

Q36. Which instrument measures zeta potential?

• Laser diffraction particle size analyzer
• Electrophoretic light scattering (zeta sizer)
• UV-visible spectrophotometer
• pH meter

Correct Answer: Electrophoretic light scattering (zeta sizer)

Q37. What happens to viscosity when shear rate increases in a pseudoplastic suspension?

• Viscosity increases
• Viscosity decreases (shear thinning)
• Viscosity remains constant
• Viscosity oscillates

Correct Answer: Viscosity decreases (shear thinning)

Q38. Which of the following is a potential incompatibility between drug and suspending agent?

• Adsorption of drug onto suspending agent decreasing available dose
• Improved drug solubility always
• Enhanced flavor only
• Automatic sterilization

Correct Answer: Adsorption of drug onto suspending agent decreasing available dose

Q39. Which measurement indicates the degree of particle settling over time?

• pH value
• Sedimentation volume and rate
• Viscosity at infinite time
• Conductivity only

Correct Answer: Sedimentation volume and rate

Q40. A suspension intended for parenteral administration must be:

• Non-sterile
• Free of particulate matter and sterile
• Colored for identification
• Highly viscous only

Correct Answer: Free of particulate matter and sterile

Q41. How does particle size affect dissolution rate of suspended drug particles?

• Larger particles dissolve faster
• Smaller particles have larger surface area and dissolve faster
• Particle size has no effect
• Only pH affects dissolution

Correct Answer: Smaller particles have larger surface area and dissolve faster

Q42. Which of the following is NOT a suspending agent?

• Tragacanth
• Alginate
• Magnesium stearate
• Carboxymethyl cellulose

Correct Answer: Magnesium stearate

Q43. Particle settling can be minimized by:

• Decreasing medium viscosity
• Increasing particle size
• Increasing viscosity of the medium using suspending agents
• Heating the suspension to evaporate solvent

Correct Answer: Increasing viscosity of the medium using suspending agents

Q44. Which process uses high shear to produce fine suspensions and reduce particle size?

• Homogenization
• Freeze-drying
• Simple shaking
• Gentle stirring only

Correct Answer: Homogenization

Q45. Which statement about surfactants in suspensions is correct?

• They increase interfacial tension
• They help wet hydrophobic particles and stabilize dispersion
• They always promote caking
• They are never used with preservatives

Correct Answer: They help wet hydrophobic particles and stabilize dispersion

Q46. Which USP test is commonly applied to suspensions?

• Dissolution testing only for tablets
• Uniformity of dosage units and microbial limits where applicable
• Only color matching test
• Melting point determination

Correct Answer: Uniformity of dosage units and microbial limits where applicable

Q47. Which factor most influences the choice between a flocculated and deflocculated suspension design?

• Desired re-dispersibility and prevention of caking
• Color preference
• Container shape only
• Storage temperature alone

Correct Answer: Desired re-dispersibility and prevention of caking

Q48. Electrostatic stabilization of particles is achieved by:

• Increasing polymer adsorption
• Imparting like surface charges to particles to repel each other
• Adding high molecular weight oils
• Removing water completely

Correct Answer: Imparting like surface charges to particles to repel each other

Q49. Which is a sign of an unstable suspension during accelerated stability testing?

• No change in appearance
• Phase separation, caking, or significant change in sedimentation
• Constant pH and assay
• Improved viscosity only

Correct Answer: Phase separation, caking, or significant change in sedimentation

Q50. For an oral suspension, which consideration is most important for patient safety?

• Palatability only
• Accurate dose delivery, microbial safety and absence of harmful particulates
• Color intensity only
• Use of the cheapest excipients only

Correct Answer: Accurate dose delivery, microbial safety and absence of harmful particulates

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