Stability of emulsions MCQs With Answer

Stability of emulsions MCQs With Answer is a focused review designed for B.Pharm students studying pharmaceutics and formulation science. This Student-friendly post covers emulsion stability concepts such as interfacial tension, emulsifying agents, HLB system, creaming, coalescence, Ostwald ripening, zeta potential, and accelerated stability testing. These keywords — emulsion stability, emulsifying agents, HLB, creaming, coalescence, and stability testing — help you revise core factors that affect formulation performance and shelf life. Each MCQ emphasizes practical implications for drug delivery, selection of stabilizers, and analytical methods used in quality control. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which phenomenon describes the upward migration of dispersed oil droplets in an oil-in-water emulsion?

• Creaming
• Coalescence
• Flocculation
• Ostwald ripening

Correct Answer: Creaming

Q2. What does HLB stand for in the context of emulsifiers?

• Hydrophile-Lipophile Balance
• High-Lipid Balance
• Hydrophobic-Low Balance
• Heat-Labile Base

Correct Answer: Hydrophile-Lipophile Balance

Q3. According to Bancroft’s rule, which phase the emulsifier should be more soluble in to form an O/W emulsion?

• Water phase
• Oil phase
• Neither phase
• Both phases equally

Correct Answer: Water phase

Q4. Which process reduces the interfacial tension between oil and water to stabilize emulsions?

• Action of surfactants
• Thermal expansion
• Mechanical filtration
• pH neutralization

Correct Answer: Action of surfactants

Q5. Which mechanism of stabilization involves preventing droplets from approaching closely by creating a polymer layer?

• Steric stabilization
• Electrostatic stabilization
• Gravitational stabilization
• Osmotic stabilization

Correct Answer: Steric stabilization

Q6. What is the main cause of Ostwald ripening in emulsions?

• Solubility differences leading to diffusion of dispersed phase molecules
• Immediate coalescence due to surfactant failure
• Phase inversion by heating
• Mechanical shear during storage

Correct Answer: Solubility differences leading to diffusion of dispersed phase molecules

Q7. Which measurement assesses the surface charge of emulsion droplets and predicts electrostatic stability?

• Zeta potential
• Viscosity
• Interfacial tension
• Conductivity

Correct Answer: Zeta potential

Q8. Which test is commonly used to detect whether an emulsion is O/W or W/O?

• Conductivity test
• pH test
• Viscosity test
• Colorimetric test

Correct Answer: Conductivity test

Q9. What effect does increasing emulsifier concentration generally have on droplet size during emulsification?

• Decreases droplet size
• Increases droplet size
• No effect on droplet size
• Causes immediate phase separation

Correct Answer: Decreases droplet size

Q10. Which phenomenon is primarily responsible for irreversible merging of droplets into a larger droplet?

• Coalescence
• Creaming
• Flocculation
• Emulsification

Correct Answer: Coalescence

Q11. Which emulsion instability is reversible and characterized by clusters of droplets held together by weak forces?

• Flocculation
• Coalescence
• Phase inversion
• Sedimentation

Correct Answer: Flocculation

Q12. Which additive is used as a viscosity enhancer to reduce creaming rate?

• Carbomer
• Sodium chloride
• Alcohol
• Magnesium stearate

Correct Answer: Carbomer

Q13. Phase inversion from O/W to W/O can be induced by which of the following?

• Excess oil addition or temperature changes
• Adding buffering agents
• Sterilization by filtration
• Using nonionic surfactants only

Correct Answer: Excess oil addition or temperature changes

Q14. Which instrument is commonly used to determine droplet size distribution in emulsions?

• Laser diffraction particle size analyzer
• pH meter
• UV-Vis spectrophotometer
• Conductivity meter

Correct Answer: Laser diffraction particle size analyzer

Q15. What role do co-surfactants play in microemulsion formation?

• Reduce interfacial tension and increase fluidity of interface
• Increase viscosity to prevent flow
• Act as preservatives
• Promote microbial growth

Correct Answer: Reduce interfacial tension and increase fluidity of interface

Q16. Which parameter is most directly related to the rate of creaming according to Stokes’ law?

• Difference in density between dispersed and continuous phases
• Color of dispersed phase
• Electrical conductivity
• pH of the continuous phase

Correct Answer: Difference in density between dispersed and continuous phases

Q17. Which surfactant type is typically used to form water-in-oil (W/O) emulsions?

• Low HLB (lipophilic) surfactants
• High HLB (hydrophilic) surfactants
• Cationic preservatives
• Water-soluble polymers

Correct Answer: Low HLB (lipophilic) surfactants

Q18. Which analytical method can monitor Ostwald ripening over time?

• Periodic measurement of droplet size distribution
• Single pH measurement
• Visual color comparison only
• Measuring melting point

Correct Answer: Periodic measurement of droplet size distribution

Q19. Which factor promotes electrostatic stabilization of emulsion droplets?

• High surface charge (zeta potential magnitude)
• Low molecular weight oils
• Neutral surfactants exclusively
• High ionic strength

Correct Answer: High surface charge (zeta potential magnitude)

Q20. What is a common preservative challenge in emulsions?

• Partitioning of preservative into oil phase reducing aqueous activity
• Increasing interfacial tension
• Enhancing steric stabilization
• Reducing droplet size

Correct Answer: Partitioning of preservative into oil phase reducing aqueous activity

Q21. Which preparation method uses high shear to reduce droplet size of emulsions?

• High-pressure homogenization
• Simple mixing by spatula
• Sedimentation
• Vacuum distillation

Correct Answer: High-pressure homogenization

Q22. What is the likely effect of increasing temperature on emulsion stability for nonionic surfactants?

• May cause phase inversion due to decreased hydrophilicity
• Always increases stability
• Has no effect on surfactant behavior
• Makes oil phase more hydrophilic

Correct Answer: May cause phase inversion due to decreased hydrophilicity

Q23. Which property of oil influences Ostwald ripening most strongly?

• Solubility of oil in continuous phase
• Color of oil
• Viscosity of continuous phase
• pH of oil

Correct Answer: Solubility of oil in continuous phase

Q24. Which type of emulsifier provides stabilization primarily through charge repulsion?

• Anionic or cationic surfactants
• Nonionic polymers
• Neutral oils
• Alcohols

Correct Answer: Anionic or cationic surfactants

Q25. Which test evaluates the physical stability of an emulsion under stress conditions over a short time?

• Accelerated stability testing (centrifugation, temperature cycling)
• Long-term clinical trial
• Antimicrobial efficacy test only
• Spectrophotometric pH scan

Correct Answer: Accelerated stability testing (centrifugation, temperature cycling)

Q26. Which term describes the spontaneous formation of a microemulsion with clear appearance?

• Microemulsion formation aided by surfactant mixture
• Opaque coarse emulsion
• Crystallization
• Gelation

Correct Answer: Microemulsion formation aided by surfactant mixture

Q27. Which factor decreases electrical double layer thickness and can reduce electrostatic stabilization?

• High ionic strength
• Low surfactant concentration
• High oil viscosity
• Low temperature

Correct Answer: High ionic strength

Q28. Which of the following is used to quantify creaming tendency?

• Creaming index or creaming volume measurement
• pH titration curve
• UV absorbance at 280 nm
• Melting point analysis

Correct Answer: Creaming index or creaming volume measurement

Q29. Which excipient can act as both an emulsifier and viscosity modifier in topical emulsions?

• Polysorbate with carbomer combination
• Sodium chloride alone
• Magnesium oxide
• Calcium carbonate

Correct Answer: Polysorbate with carbomer combination

Q30. What is the effect of droplet size reduction on emulsion stability?

• Generally increases kinetic stability by reducing creaming and coalescence rates
• Always causes rapid phase separation
• Increases Ostwald ripening only
• Has no effect on viscosity

Correct Answer: Generally increases kinetic stability by reducing creaming and coalescence rates

Q31. Which condition may promote microbial growth in emulsions if preservative partitioning is inadequate?

• High water activity and poor preservative availability in aqueous phase
• Presence of only lipophilic preservatives
• Low pH below 3
• High oil viscosity

Correct Answer: High water activity and poor preservative availability in aqueous phase

Q32. Which rheological property is helpful to resist creaming in emulsions?

• Higher continuous-phase viscosity
• Lower interfacial tension
• Higher electrical conductivity
• Lower droplet charge

Correct Answer: Higher continuous-phase viscosity

Q33. Which analytical technique can map the spatial distribution of phases in an emulsion?

• Confocal laser scanning microscopy
• pH indicator strips
• Simple light bulb illumination
• Gravimetric analysis

Correct Answer: Confocal laser scanning microscopy

Q34. Which component is most likely to cause emulsion phase inversion upon dilution?

• High concentration of surfactant with particular HLB
• Nonvolatile preservatives
• Viscosity enhancers at low concentration
• Trace metals

Correct Answer: High concentration of surfactant with particular HLB

Q35. Which of the following reduces Ostwald ripening when added to the oil phase?

• A less soluble oil to reduce dispersed phase solubility
• A volatile solvent
• An ionic salt
• Water-miscible alcohol

Correct Answer: A less soluble oil to reduce dispersed phase solubility

Q36. Which parameter is not directly affected by the emulsifier type?

• Intrinsic melting point of the oil phase
• Interfacial tension
• Droplet size distribution
• Stability against coalescence

Correct Answer: Intrinsic melting point of the oil phase

Q37. Which surfactant class is least sensitive to changes in ionic strength for stabilization?

• Nonionic surfactants
• Anionic surfactants
• Cationic surfactants
• Zwitterionic surfactants

Correct Answer: Nonionic surfactants

Q38. Which stability issue is primary concern during freeze-thaw cycles?

• Phase separation due to ice crystallization and surfactant redistribution
• Immediate oxidation of oil
• Increase in HLB value permanently
• Permanent polymerization of emulsifier

Correct Answer: Phase separation due to ice crystallization and surfactant redistribution

Q39. Which laboratory test distinguishes microemulsions from conventional emulsions?

• Translucency and thermodynamic stability assessment
• Color test with iodine
• pH less than 2
• Smell evaluation only

Correct Answer: Translucency and thermodynamic stability assessment

Q40. Which of the following increases the rate of creaming according to Stokes’ law?

• Decreasing continuous phase viscosity
• Decreasing droplet size
• Matching densities of phases
• Adding finer emulsifier particles

Correct Answer: Decreasing continuous phase viscosity

Q41. Which mechanism explains stabilization by charged surfactants?

• Electrical double layer repulsion
• Chemical cross-linking of droplets
• Spontaneous polymerization
• Magnetic alignment

Correct Answer: Electrical double layer repulsion

Q42. Which parameter should be monitored to evaluate long-term physical stability of pharmaceutical emulsions?

• Droplet size distribution over time
• Melting point of oil
• UV absorbance at 600 nm only once
• Initial pH exclusively

Correct Answer: Droplet size distribution over time

Q43. Which excipient helps form a barrier film around droplets to provide steric stabilization?

• Hydrophilic polymers like PEG or PVA
• Simple salts like NaCl
• Heavy metals
• Low molecular weight alcohols

Correct Answer: Hydrophilic polymers like PEG or PVA

Q44. Which factor would most likely decrease interfacial tension effectively?

• Adding appropriate surfactant or surfactant blend
• Raising pH beyond surfactant stability range
• Adding insoluble fillers
• Reducing temperature below freezing

Correct Answer: Adding appropriate surfactant or surfactant blend

Q45. Which of the following is a sign of partial coalescence in an emulsion?

• Formation of oil globules with irregular shapes and trapped smaller droplets
• Complete transparency
• Measured zero zeta potential always
• Instantaneous gelation of the continuous phase

Correct Answer: Formation of oil globules with irregular shapes and trapped smaller droplets

Q46. Which design change can reduce creaming without changing emulsifier chemistry?

• Increase continuous phase viscosity using thickeners
• Decrease storage temperature below freezing
• Replace oil with water
• Remove preservatives

Correct Answer: Increase continuous phase viscosity using thickeners

Q47. Which surfactant HLB value is suitable for stabilizing an O/W emulsion?

• High HLB (e.g., 8–18)
• Very low HLB (e.g., 1–3)
• HLB is irrelevant
• Negative HLB values

Correct Answer: High HLB (e.g., 8–18)

Q48. Which phenomenon is measured when using a creaming index after centrifugation?

• Relative tendency for phase separation under accelerated gravity
• pH stability under shear
• Chemical degradation rate
• Color change intensity

Correct Answer: Relative tendency for phase separation under accelerated gravity

Q49. Which ingredient selection reduces the risk of Ostwald ripening in oil-in-water emulsions?

• Use of oils with very low solubility in water
• Use of volatile oils only
• High water-miscible solvents
• High salt concentration only

Correct Answer: Use of oils with very low solubility in water

Q50. Which practice is important for regulatory quality control of pharmaceutical emulsions?

• Routine stability testing including droplet size, pH, viscosity, and microbial limits
• Only organoleptic testing
• Discarding any emulsion older than one day without testing
• Not documenting storage conditions

Correct Answer: Routine stability testing including droplet size, pH, viscosity, and microbial limits

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