Formulation of suspensions MCQs With Answer

Formulation of suspensions MCQs With Answer

This concise, topic-focused introduction covers suspension formulation key concepts for B.Pharm students: suspension definition, particle size reduction, wetting agents, suspending agents, flocculation, sedimentation, zeta potential, rheology, preservatives, and stability testing. Emphasis is on practical formulation strategies—choosing suspending agents (xanthan, methylcellulose, bentonite), controlling particle size (milling, micronization), manipulating double layer and electrolytes to control flocculation, and improving redispersibility. Understanding these critical quality attributes helps predict physical stability, prevent caking, and ensure safe, effective oral suspensions. This primer is keyword-rich and exam-oriented to aid classroom learning and revision. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What best defines a pharmaceutical suspension?

• A coarse dispersion of solid particles in a liquid medium
• A true solution of solute molecules in a solvent
• A single-phase homogeneous mixture
• An emulsion of two immiscible liquids

Correct Answer: A coarse dispersion of solid particles in a liquid medium

Q2. What is the primary role of a suspending agent in oral suspensions?

• Increase viscosity to reduce sedimentation
• Act as a preservative to prevent microbial growth
• Enhance drug solubility by chemical reaction
• Promote rapid absorption through the GI tract

Correct Answer: Increase viscosity to reduce sedimentation

Q3. Which statement correctly describes flocculation in suspensions?

• Formation of loose, reversible aggregates that are easy to redisperse
• Irreversible fusion of particles forming a hard cake
• Complete dissolution of particles into the continuous phase
• Separation of immiscible liquid phases

Correct Answer: Formation of loose, reversible aggregates that are easy to redisperse

Q4. A deflocculated suspension typically shows which characteristic?

• Forms a compact sediment that is difficult to redisperse
• Forms a loose, fluffy sediment that is easily redispersed
• Immediate chemical degradation of the API
• Rapid creaming with oil separation

Correct Answer: Forms a compact sediment that is difficult to redisperse

Q5. Which approach commonly induces flocculation in a suspension?

• Addition of electrolytes to compress the electrical double layer
• Increasing particle charge to maximize repulsion
• Sterilizing by autoclaving
• Lowering viscosity to allow faster settling

Correct Answer: Addition of electrolytes to compress the electrical double layer

Q6. According to Stokes’ law, sedimentation velocity is proportional to which factor?

• The square of the particle radius
• The particle radius to the first power
• The cube of particle mass
• The logarithm of particle diameter

Correct Answer: The square of the particle radius

Q7. What does a high magnitude zeta potential indicate for a suspension?

• High electrostatic repulsion and increased stability against flocculation
• Rapid aggregation and caking tendency
• Low surface charge and immediate creaming
• Complete solubilization of particles

Correct Answer: High electrostatic repulsion and increased stability against flocculation

Q8. The primary function of a wetting agent in suspension formulation is:

• Reduce contact angle to improve wettability of hydrophobic powders
• Increase pH to dissolve the drug
• Cross-link polymer chains to form a gel
• Act as a flavoring agent to mask taste

Correct Answer: Reduce contact angle to improve wettability of hydrophobic powders

Q9. How is sedimentation volume (F) defined?

• The ratio of ultimate sediment volume to the original total volume (Vu/Vo)
• The mass of sediment per unit time
• The initial volume divided by the final volume
• The concentration of suspended solids in the supernatant

Correct Answer: The ratio of ultimate sediment volume to the original total volume (Vu/Vo)

Q10. Degree of flocculation (β) is calculated as:

• The ratio of sedimentation volume of flocculated suspension to deflocculated suspension
• The product of particle diameter and zeta potential
• The inverse of viscosity at zero shear
• The percentage of dissolved drug after 24 hours

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

Q11. Which of the following are commonly used suspending agents?

• Xanthan gum, methylcellulose, carbomers, bentonite
• Sodium chloride, glucose, ethanol, acetone
• Parabens, benzalkonium chloride, sodium benzoate, sorbic acid
• Titanium dioxide, talc, magnesium stearate, lactose

Correct Answer: Xanthan gum, methylcellulose, carbomers, bentonite

Q12. Key requirement for a preservative used in aqueous suspensions is:

• Compatibility with formulation and broad-spectrum antimicrobial efficacy
• High reactivity with the active drug to form adducts
• Complete insolubility in the continuous phase
• Being a strong oxidizing agent

Correct Answer: Compatibility with formulation and broad-spectrum antimicrobial efficacy

Q13. Why are dry powders for reconstitution used for some suspensions?

• They improve physical and chemical stability and reduce microbial growth until reconstitution
• They immediately dissolve to provide a true solution on storage
• They require high temperature storage to remain stable
• They eliminate the need for preservatives entirely

Correct Answer: They improve physical and chemical stability and reduce microbial growth until reconstitution

Q14. Ostwald ripening in suspensions refers to:

• Growth of larger particles at the expense of smaller ones via dissolution and reprecipitation
• Immediate chemical degradation of suspended particles
• Formation of insoluble salts between drug and excipients
• Reversible flocculation due to polymer bridging

Correct Answer: Growth of larger particles at the expense of smaller ones via dissolution and reprecipitation

Q15. Creaming differs from sedimentation because:

• Creaming is upward migration when suspended phase is less dense than the medium
• Creaming results from microbial spoilage
• Creaming requires heating to occur
• Creaming produces an irreversible hard cake

Correct Answer: Creaming is upward migration when suspended phase is less dense than the medium

Q16. How can pH influence suspension stability?

• By changing ionization of particle surfaces and zeta potential, altering aggregation
• By converting solids into gases
• By making suspending agents evaporate
• By increasing particle density uniformly

Correct Answer: By changing ionization of particle surfaces and zeta potential, altering aggregation

Q17. The effect of adding electrolytes to a charged suspension is primarily to:

• Compress the electrical double layer and promote flocculation
• Increase the viscosity dramatically to prevent settling
• Sterilize the formulation by ionic disruption
• Convert solids into soluble salts instantly

Correct Answer: Compress the electrical double layer and promote flocculation

Q18. Which equipment is commonly used for particle size reduction in suspension manufacture?

• Colloid mill or high-shear homogenizer
• Freeze dryer
• Gas chromatograph
• Lyophilizer

Correct Answer: Colloid mill or high-shear homogenizer

Q19. Nonionic surfactants such as polysorbates (Tween) primarily act as:

• Wetting agents that reduce surface tension and aid dispersion
• Strong oxidizing preservatives
• Cross-linkers for polymeric gels
• Density modifiers to cause creaming

Correct Answer: Wetting agents that reduce surface tension and aid dispersion

Q20. Which rheological behavior is most desirable in oral suspensions?

• Pseudoplastic with thixotropy to allow pourability and reduce sedimentation
• Bingham plastic with permanent hardening
• Newtonian low viscosity to ensure rapid settling
• Highly elastic solid-like behavior at all shear rates

Correct Answer: Pseudoplastic with thixotropy to allow pourability and reduce sedimentation

Q21. When selecting a preservative for a suspension, which factor is critical?

• Effectiveness at the formulation’s pH and compatibility with excipients
• Ability to increase particle size on storage
• Complete insolubility in the aqueous phase
• Strong chelating properties to remove metal ions

Correct Answer: Effectiveness at the formulation’s pH and compatibility with excipients

Q22. Typical accelerated stability conditions used to screen suspensions are:

• 40°C and 75% relative humidity for defined periods
• 0°C with 100% relative humidity
• Autoclaving at 121°C for 30 minutes
• Exposure to direct sunlight for 6 hours

Correct Answer: 40°C and 75% relative humidity for defined periods

Q23. Which formulation approach improves redispersibility of sedimented suspensions?

• Promoting controlled flocculation to form loose, porous sediments
• Maximizing deflocculation to create a dense cake
• Increasing the oil content to form emulsions
• Removing all suspending agents to reduce viscosity

Correct Answer: Promoting controlled flocculation to form loose, porous sediments

Q24. According to Stokes’ law, which change will decrease sedimentation rate?

• Increasing the viscosity of the continuous phase
• Increasing particle radius significantly
• Decreasing the density difference between particle and medium
• Both increasing viscosity and decreasing particle size

Correct Answer: Both increasing viscosity and decreasing particle size

Q25. A contact angle less than 90° between particle and liquid indicates:

• Good wettability of the particle by the liquid
• Poor wettability and formation of air pockets
• Immediate precipitation of dissolved APIs
• Formation of a hard, irreversible cake

Correct Answer: Good wettability of the particle by the liquid

Q26. Which natural polymer is commonly used as an oral suspending agent?

• Xanthan gum
• Polyethylene glycol 400
• Benzyl alcohol
• Sodium chloride

Correct Answer: Xanthan gum

Q27. How do wetting agents improve incorporation of hydrophobic powders into a liquid?

• Displace air at particle surface and allow liquid penetration
• React chemically to dissolve the particles completely
• Convert the powder into gaseous form
• Increase particle density to prevent creaming

Correct Answer: Displace air at particle surface and allow liquid penetration

Q28. If particle diameter is halved, how does Stokes’ sedimentation velocity change (assuming other factors constant)?

• It becomes one quarter of the original velocity
• It doubles
• It remains the same
• It becomes eight times smaller

Correct Answer: It becomes one quarter of the original velocity

Q29. Which preservative is known to be incompatible with anionic surfactants like sodium lauryl sulfate?

• Benzalkonium chloride (a cationic preservative)
• Parabens (methylparaben, propylparaben)
• Sorbic acid
• Sodium benzoate

Correct Answer: Benzalkonium chloride (a cationic preservative)

Q30. Which analytical technique is commonly used to measure zeta potential of suspended particles?

• Electrophoretic light scattering (ELS)
• High-performance liquid chromatography (HPLC)
• Mass spectrometry (MS)
• Ultraviolet-visible spectroscopy (UV-Vis)

Correct Answer: Electrophoretic light scattering (ELS)

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