HLB scale MCQs With Answer

Introduction: The HLB scale MCQs With Answer are essential study material for B. Pharm students learning surfactant selection, emulsion design, and formulation stability. This concise, keyword-rich introduction explains the Hydrophilic-Lipophilic Balance (HLB) concept, methods for HLB calculation (Griffin and Davies), and practical use of HLB to choose emulsifiers like Tweens and Spans for O/W and W/O systems. Understanding required HLB of oils, mixing surfactants to reach target HLB, and evaluating emulsion stability helps optimize drug delivery and topical formulations. These HLB questions emphasize calculations, selection strategy, and real-world formulation implications. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What does the HLB scale primarily measure in surfactants?

• The molecular weight of surfactants
• The balance between hydrophilic and lipophilic portions
• The melting point of surfactants
• The pH sensitivity of surfactants

Correct Answer: The balance between hydrophilic and lipophilic portions

Q2. Which HLB value range typically favors oil-in-water (O/W) emulsions?

• 0–3
• 3–7
• 8–18
• 19–25

Correct Answer: 8–18

Q3. According to Griffin’s method, how is HLB of a non-ionic surfactant calculated?

• HLB = 7 + sum of group values
• HLB = 20 × (mass of hydrophilic portion / molecular mass of molecule)
• HLB = 100 × (hydrophilic % by weight)
• HLB = (lipophilic groups × 10) / total groups

Correct Answer: HLB = 20 × (mass of hydrophilic portion / molecular mass of molecule)

Q4. What is the practical use of determining the required HLB of an oil phase?

• To measure oil viscosity
• To select appropriate emulsifier(s) for stable emulsions
• To determine drug solubility in water
• To estimate oil density

Correct Answer: To select appropriate emulsifier(s) for stable emulsions

Q5. Which surfactant is commonly reported to have an HLB of about 15.0?

• Sorbitan monooleate (Span 80)
• Polysorbate 80 (Tween 80)
• Sorbitan monostearate (Span 60)
• Glyceryl monostearate

Correct Answer: Polysorbate 80 (Tween 80)

Q6. Which surfactant is commonly reported to have an HLB around 4.3?

• Polysorbate 20 (Tween 20)
• Sorbitan monooleate (Span 80)
• Poloxamer 188
• Polyethylene glycol

Correct Answer: Sorbitan monooleate (Span 80)

Q7. How do you calculate the HLB of a blend of two surfactants?

• Multiply the HLBs then divide by two
• Take the average of the two HLB values irrespective of proportions
• Sum(weight fraction × HLB of each surfactant)
• Use the lowest HLB value only

Correct Answer: Sum(weight fraction × HLB of each surfactant)

Q8. If Tween 80 (HLB 15.0) and Span 80 (HLB 4.3) are mixed to give a blend HLB of 10, approximately what weight percent of Tween 80 is required?

• About 25% Tween 80 and 75% Span 80
• About 53% Tween 80 and 47% Span 80
• About 80% Tween 80 and 20% Span 80
• About 10% Tween 80 and 90% Span 80

Correct Answer: About 53% Tween 80 and 47% Span 80

Q9. Which method assigns HLB by summing group contribution values?

• Griffin method
• Davies method
• Phase inversion method
• Hansen solubility method

Correct Answer: Davies method

Q10. Davies method expresses HLB as which of the following formulas?

• HLB = 20 × (hydrophilic mass / molecular mass)
• HLB = 7 + Σ(hydrophilic group values) − Σ(lipophilic group values)
• HLB = log P of surfactant
• HLB = (number of ethylene oxide units) × 2

Correct Answer: HLB = 7 + Σ(hydrophilic group values) − Σ(lipophilic group values)

Q11. For a W/O emulsion, which HLB range is generally preferred for the emulsifier?

• 10–20
• 8–12
• 3–7
• 18–25

Correct Answer: 3–7

Q12. Which statement is true about the HLB number as an intrinsic property?

• HLB is strongly temperature dependent and varies widely with pH
• HLB is a fixed theoretical index for a surfactant but performance can vary with conditions
• HLB measures surfactant toxicity
• HLB is identical for ionic and non-ionic surfactants always

Correct Answer: HLB is a fixed theoretical index for a surfactant but performance can vary with conditions

Q13. What is an experimental approach to determine the required HLB of an oil?

• Measuring oil refractive index
• Testing a series of emulsions prepared with surfactant blends of varying HLB and evaluating stability
• Estimating from oil color
• Calculating from molecular weight only

Correct Answer: Testing a series of emulsions prepared with surfactant blends of varying HLB and evaluating stability

Q14. Which of the following surfactant pairs are classical examples used for O/W emulsions?

• Span 80 and mineral oil
• Tween 80 and Span 80
• Span 60 and liquid paraffin only
• Poloxamer and cholesterol

Correct Answer: Tween 80 and Span 80

Q15. What effect does selecting an HLB close to the required HLB of an oil have on emulsion droplets?

• Increases droplet size and reduces stability
• Minimizes interfacial tension and tends to give smaller, more stable droplets
• Eliminates the need for homogenization
• Only affects color, not droplet size

Correct Answer: Minimizes interfacial tension and tends to give smaller, more stable droplets

Q16. Polysorbate 20 (Tween 20) typically has an HLB closest to which value?

• 4.3
• 8.6
• 16.7
• 2.0

Correct Answer: 16.7

Q17. Span 20 (sorbitan monolaurate) is commonly listed with an HLB of approximately:

• 8.6
• 16.7
• 4.3
• 12.5

Correct Answer: 8.6

Q18. When blending three surfactants, how is the overall HLB calculated?

• Average the HLBs without weighting
• Sum(weight fraction × HLB) for all three surfactants
• Use the HLB of the surfactant with the highest value only
• Add all HLB numbers and divide by three

Correct Answer: Sum(weight fraction × HLB) for all three surfactants

Q19. Which factor is NOT directly described by the HLB value?

• Relative hydrophilicity or lipophilicity
• Emulsion type preference (O/W vs W/O)
• Exact emulsification speed in minutes
• Guidance for surfactant selection

Correct Answer: Exact emulsification speed in minutes

Q20. A formulator needs a blend HLB of 12. Using Span 20 (HLB 8.6) and Tween 20 (HLB 16.7), approximately what percent Tween 20 is needed?

• About 20% Tween 20
• About 42% Tween 20
• About 75% Tween 20
• About 90% Tween 20

Correct Answer: About 42% Tween 20

Q21. Which property of non-ionic ethoxylated surfactants may change with temperature, affecting emulsion performance?

• HLB numerical index
• Cloud point and hydration of ethylene oxide chains
• The number of carbon atoms
• Atomic weight

Correct Answer: Cloud point and hydration of ethylene oxide chains

Q22. Which surfactant is more lipophilic based on HLB: Span 60 (HLB ~4.7) or Tween 60 (HLB ~14.9)?

• Span 60 is more lipophilic
• Tween 60 is more lipophilic
• Both are equally lipophilic
• HLB does not indicate lipophilicity

Correct Answer: Span 60 is more lipophilic

Q23. If an oil has a required HLB of 10.5, which surfactant system is likely appropriate?

• Pure Span with HLB 4
• Blend of surfactants adjusted to HLB ~10.5
• No surfactant needed
• Use only ionic surfactants with HLB <3

Correct Answer: Blend of surfactants adjusted to HLB ~10.5

Q24. In practice, why might the theoretical HLB not guarantee optimal stability?

• Because HLB cannot predict interfacial film strength, viscosity, and phase behavior
• Because HLB is the only factor determining stability
• Because HLB is always wrong
• Because surfactants are never pure

Correct Answer: Because HLB cannot predict interfacial film strength, viscosity, and phase behavior

Q25. What is the conceptual midpoint of the HLB scale and what does it indicate?

• 0 indicates fully hydrophilic
• 10 indicates balanced hydrophilic-lipophilic character
• 20 indicates fully lipophilic
• 50 indicates maximum surfactant power

Correct Answer: 10 indicates balanced hydrophilic-lipophilic character

Q26. Which experimental observation indicates that you have reached the required HLB during screening?

• Maximum creaming and phase separation
• Lowest observed droplet size and best physical stability
• Highest oil discoloration
• Complete dissolution of oil in water

Correct Answer: Lowest observed droplet size and best physical stability

Q27. When combining a high-HLB surfactant with a low-HLB surfactant, what is the main purpose?

• To increase oil viscosity
• To tailor the blend HLB to the required value of the oil
• To change the color of the emulsion
• To raise the melting point of surfactants

Correct Answer: To tailor the blend HLB to the required value of the oil

Q28. If a surfactant has an HLB of 2, what type of emulsifier is it?

• Strongly hydrophilic
• Moderately hydrophilic
• Strongly lipophilic (oil-soluble)
• Ionic cationic surfactant

Correct Answer: Strongly lipophilic (oil-soluble)

Q29. Which of these is a limitation of the HLB system?

• It accounts for interfacial film elasticity fully
• It does not include the effect of electrolytes, temperature, or co-surfactants comprehensively
• It precisely predicts long-term chemical stability
• It determines pharmacological activity of excipients

Correct Answer: It does not include the effect of electrolytes, temperature, or co-surfactants comprehensively

Q30. A researcher wants a W/O emulsion using mineral oil; which surfactant HLB should they generally target?

• 12–16
• 8–10
• 3–6
• 18–20

Correct Answer: 3–6

Q31. What is the expected HLB behavior of ionic surfactants compared to non-ionic in the classical HLB system?

• Ionic surfactants do not have HLB values
• Ionic surfactants are assigned HLB approximately by considering their water solubility but are less predictable by Griffin’s method
• Ionic surfactants always have HLB > 20
• Ionic surfactants always have HLB = 0

Correct Answer: Ionic surfactants are assigned HLB approximately by considering their water solubility but are less predictable by Griffin’s method

Q32. Which of the following is a correct practical step when screening surfactants based on HLB?

• Prepare emulsions with a single surfactant only and ignore blends
• Prepare a series of emulsions with varying blend HLB values and assess stability parameters
• Only use HLB numbers without laboratory testing
• Choose surfactants by color matching

Correct Answer: Prepare a series of emulsions with varying blend HLB values and assess stability parameters

Q33. A formulator blends Span 60 (HLB 4.7) and Tween 60 (HLB 14.9) in equal weights. What is the HLB of the blend?

• 4.7
• 14.9
• 9.8
• 19.6

Correct Answer: 9.8

Q34. Which of the following oils typically requires a relatively low required HLB for stabilization (i.e., favors W/O)?

• Short-chain triglycerides with required HLB ~3–6
• Highly polar oils with required HLB ~18
• Pure water
• Glycerin

Correct Answer: Short-chain triglycerides with required HLB ~3–6

Q35. How does adding a co-surfactant (co-emulsifier) affect HLB-based formulation?

• It has no effect on interfacial properties
• It can modify interfacial film flexibility and change the effective performance even if HLB remains similar
• It always increases HLB by 10 units
• It prevents emulsification entirely

Correct Answer: It can modify interfacial film flexibility and change the effective performance even if HLB remains similar

Q36. Which analytical observation suggests poor surfactant choice despite matching theoretical HLB?

• Good creaming resistance and small droplets
• Rapid phase separation or coalescence within hours
• Long-term stability with no change
• Optimal viscosity for application

Correct Answer: Rapid phase separation or coalescence within hours

Q37. Why is HLB teaching important for B. Pharm students?

• It helps predict drug chemical structure
• It guides excipient selection for stable topical and parenteral emulsions and drug delivery systems
• It is only theoretical with no practical use
• It determines patient compliance directly

Correct Answer: It guides excipient selection for stable topical and parenteral emulsions and drug delivery systems

Q38. Which of the following is true about surfactant pairs Tween/Span in HLB practice?

• Tweens are typically lipophilic while Spans are hydrophilic
• Tweens are typically hydrophilic (high HLB) while Spans are lipophilic (low HLB)
• Tweens and Spans have identical HLB values
• They cannot be blended

Correct Answer: Tweens are typically hydrophilic (high HLB) while Spans are lipophilic (low HLB)

Q39. Which outcome indicates that the HLB of the surfactant blend is too hydrophilic for a given oil?

• Formation of a stable W/O emulsion
• Phase inversion to O/W or formation of microemulsion oil droplets in water
• Color change of oil without emulsion
• No emulsification at all

Correct Answer: Phase inversion to O/W or formation of microemulsion oil droplets in water

Q40. A blend of surfactants has HLB 11. If the required HLB of oil is 7, what is the likely consequence?

• The blend is too lipophilic and will form W/O easily
• The blend is too hydrophilic, may favor O/W or be unsuitable for stable W/O
• The blend will chemically react with oil
• HLB difference has no consequence

Correct Answer: The blend is too hydrophilic, may favor O/W or be unsuitable for stable W/O

Q41. During HLB-guided screening, which viscosity-related factor should be considered for topical creams?

• Viscosity is irrelevant for topical products
• Appropriate rheology modifiers may be needed to balance emulsion stability and application feel, even at correct HLB
• Viscosity is determined solely by HLB number
• Lower viscosity always means more stable emulsion

Correct Answer: Appropriate rheology modifiers may be needed to balance emulsion stability and application feel, even at correct HLB

Q42. Which surfactant would you choose for high hydrophilicity based on HLB values?

• Span 80 (HLB 4.3)
• Span 60 (HLB 4.7)
• Tween 20 (HLB 16.7)
• Sorbitan monolaurate (HLB 8.6)

Correct Answer: Tween 20 (HLB 16.7)

Q43. If you want to prepare a water-in-oil microemulsion, which HLB strategy is most appropriate?

• Use only high-HLB surfactants (>15) for stability
• Aim for a low to moderate HLB blend appropriate to the oil, often in the range 3–7
• Avoid surfactants altogether
• Use ionic surfactants exclusively regardless of HLB

Correct Answer: Aim for a low to moderate HLB blend appropriate to the oil, often in the range 3–7

Q44. Which of the following best describes the role of HLB in formulating parenteral emulsions?

• Irrelevant due to sterile filtration
• Critical for selecting emulsifiers that minimize droplet growth and ensure physical stability
• Determines antiseptic activity
• Used only to decide container type

Correct Answer: Critical for selecting emulsifiers that minimize droplet growth and ensure physical stability

Q45. For a target HLB of 9.8, you blend Span 60 (HLB 4.7) and Tween 60 (HLB 14.9). What weight ratio of Tween 60 is needed if mixed 1:1 achieves 9.8?

• The 1:1 (50% Tween 60) mixture gives HLB 9.8, so 50% Tween 60
• 0% Tween 60
• 100% Tween 60
• 25% Tween 60

Correct Answer: The 1:1 (50% Tween 60) mixture gives HLB 9.8, so 50% Tween 60

Q46. Which of the following is a correct interpretation: a surfactant with HLB 14 is:

• Predominantly lipophilic and ideal for W/O
• Predominantly hydrophilic and suitable as O/W emulsifier
• Neutral and not surface active
• Highly viscous

Correct Answer: Predominantly hydrophilic and suitable as O/W emulsifier

Q47. Which experimental technique helps evaluate emulsion stability during HLB screening?

• Thermogravimetric analysis only
• Droplet size distribution by microscopy or laser diffraction and accelerated stability tests
• pH titration alone
• Measuring melting point of surfactant

Correct Answer: Droplet size distribution by microscopy or laser diffraction and accelerated stability tests

Q48. If a binary surfactant blend gives phase separation quickly, what formulation adjustments should you consider?

• Change oil phase, modify surfactant ratio to match required HLB, or add co-surfactant and rheology modifier
• Decrease temperature to absolute zero
• Remove all surfactant and rely on agitation only
• Double the oil volume only

Correct Answer: Change oil phase, modify surfactant ratio to match required HLB, or add co-surfactant and rheology modifier

Q49. Which of the following best summarizes why HLB is helpful for B. Pharm students?

• It replaces all laboratory testing
• It provides a practical guideline for selecting and blending emulsifiers to design stable pharmaceutical emulsions
• It indicates drug efficacy directly
• It measures particle charge accurately

Correct Answer: It provides a practical guideline for selecting and blending emulsifiers to design stable pharmaceutical emulsions

Q50. A formulation requires a blend HLB of 10.5. You have surfactants with HLB 14.9 (Tween 60) and 4.7 (Span 60). Approximately what percent of Tween 60 is needed?

• About 10% Tween 60
• About 57% Tween 60 and 43% Span 60
• About 90% Tween 60
• About 25% Tween 60

Correct Answer: About 57% Tween 60 and 43% Span 60

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