Spreading coefficient MCQs With Answer

Spreading coefficient MCQs With Answer

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Spreading coefficient MCQs With Answer offers B. Pharm students a focused, exam-oriented guide to understand how liquids behave on solid and liquid surfaces. This introduction covers key concepts like spreading coefficient definition, formulas, Young’s equation, contact angle, surfactant effects, and measurement techniques used in pharmaceutics and formulation science. Emphasis on practical relevance—wetting of powders, coating, emulsification, and transdermal delivery—helps link theory to lab practice. Clear, keyword-rich content supports searchability for students preparing for pharmacology, pharmaceutics, and physical pharmacy exams. Sharpen your conceptual understanding and calculation skills with targeted practice questions. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the spreading coefficient in pharmaceutics?

  • A measure of a liquid’s tendency to spread on a surface
  • The viscosity of a liquid at the interface
  • The density difference between two phases
  • The rate of evaporation of a solvent

Correct Answer: A measure of a liquid’s tendency to spread on a surface

Q2. Which expression correctly represents the spreading coefficient S for a liquid on a solid surface?

  • S = γ_L – (γ_S + γ_SL)
  • S = γ_S – (γ_SL + γ_L)
  • S = γ_SL – (γ_S + γ_L)
  • S = γ_S + γ_L + γ_SL

Correct Answer: S = γ_S – (γ_SL + γ_L)

Q3. What condition of the spreading coefficient indicates spontaneous complete spreading?

  • S < 0
  • S = 0
  • S > 0
  • S = -1

Correct Answer: S > 0

Q4. Using Young’s equation, which relation connects the spreading coefficient S to contact angle θ and liquid surface tension γ_L?

  • S = γ_L(1 + cosθ)
  • S = γ_L(cosθ – 1)
  • S = γ_L(sinθ – 1)
  • S = γ_L/(1 + cosθ)

Correct Answer: S = γ_L(cosθ – 1)

Q5. Which statement about S = 0 is correct for a droplet on a solid surface?

  • It indicates partial wetting with finite contact angle
  • It always indicates non-wetting
  • It corresponds to a contact angle of zero (perfect wetting)
  • It implies infinite surface tension

Correct Answer: It corresponds to a contact angle of zero (perfect wetting)

Q6. What is Young’s equation for a liquid on a rigid solid surface?

  • γ_L = γ_S + γ_SL cosθ
  • γ_S = γ_SL + γ_L cosθ
  • γ_SL = γ_S + γ_L cosθ
  • γ_S = γ_L + γ_SL sinθ

Correct Answer: γ_S = γ_SL + γ_L cosθ

Q7. Which experimental method is commonly used to measure the contact angle needed to calculate spreading coefficient?

  • Wilhelmy plate method
  • Sessile drop method
  • Brookfield viscometry
  • HPLC analysis

Correct Answer: Sessile drop method

Q8. How do surfactants generally affect the spreading coefficient of a liquid formulation?

  • They increase γ_L and reduce spreading
  • They reduce γ_L and promote spreading
  • They increase γ_SL and prevent spreading
  • They have no effect on interfacial properties

Correct Answer: They reduce γ_L and promote spreading

Q9. For a liquid A spreading on liquid B, which formula typically represents the spreading coefficient S?

  • S = γ_A – (γ_B + γ_AB)
  • S = γ_B – (γ_A + γ_AB)
  • S = γ_AB – (γ_A + γ_B)
  • S = γ_A + γ_B – γ_AB

Correct Answer: S = γ_B – (γ_A + γ_AB)

Q10. What is the Marangoni effect in the context of spreading?

  • Tendency of particles to aggregate at the interface
  • Flow driven by surface tension gradients that affects spreading
  • Diffusion of solute within the bulk liquid only
  • Chemical degradation at the interface

Correct Answer: Flow driven by surface tension gradients that affects spreading

Q11. If γ_S = 50 mN/m, γ_SL = 10 mN/m and γ_L = 30 mN/m, what is the spreading coefficient S?

  • 10 mN/m (spreads)
  • -10 mN/m (does not spread)
  • 0 mN/m (neutral)
  • 20 mN/m

Correct Answer: 10 mN/m (spreads)

Q12. Which factor does NOT directly influence the spreading coefficient?

  • Surface roughness of the solid
  • Ambient temperature
  • Surface tension of the liquid
  • Color of the liquid

Correct Answer: Color of the liquid

Q13. Contact angle hysteresis affects spreading because:

  • Advancing and receding contact angles differ, altering observed spread
  • It increases bulk viscosity of the liquid
  • It changes the chemical composition of the solid
  • It neutralizes surface tension completely

Correct Answer: Advancing and receding contact angles differ, altering observed spread

Q14. A positive spreading coefficient implies which of the following regarding contact angle?

  • Contact angle less than 90° and usually approaching 0°
  • Contact angle greater than 90°
  • Contact angle exactly 180°
  • Contact angle independent of spreading

Correct Answer: Contact angle less than 90° and usually approaching 0°

Q15. In emulsion formulation, spreading coefficient helps predict:

  • Whether an oil phase will spread over aqueous phase or form droplets
  • The pH stability of the emulsion
  • The color stability under light
  • The microbial contamination level

Correct Answer: Whether an oil phase will spread over aqueous phase or form droplets

Q16. Which instrument is primarily used to measure surface/interfacial tension directly?

  • Contact angle goniometer
  • Tensiometer
  • Spectrophotometer
  • Viscometer

Correct Answer: Tensiometer

Q17. How does temperature generally affect surface tension and thus spreading?

  • Temperature increase generally raises surface tension, reducing spreading
  • Temperature increase generally lowers surface tension, promoting spreading
  • Temperature has no effect on surface tension
  • Surface tension oscillates unpredictably with temperature

Correct Answer: Temperature increase generally lowers surface tension, promoting spreading

Q18. Which is a practical pharmaceutical application of spreading coefficient concepts?

  • Predicting tablet compression force
  • Designing topical formulations for better skin coverage
  • Quantifying drug potency in capsules
  • Measuring blood–brain barrier penetration

Correct Answer: Designing topical formulations for better skin coverage

Q19. If liquid surface tension γ_L = 40 mN/m and contact angle θ = 60°, what is S (use S = γ_L(cosθ – 1))? (cos60° = 0.5)

  • S = -20 mN/m
  • S = 20 mN/m
  • S = 0 mN/m
  • S = -10 mN/m

Correct Answer: S = -20 mN/m

Q20. What is the effect of surface-active impurities on spreading?

  • They raise γ_L and prevent spreading
  • They adsorb at interfaces, typically lowering γ_L and enhancing spreading
  • They solidify the interface immediately
  • They only affect bulk viscosity and not spreading

Correct Answer: They adsorb at interfaces, typically lowering γ_L and enhancing spreading

Q21. Which term describes the interfacial tension between a solid and a liquid?

  • γ_S
  • γ_L
  • γ_SL
  • γ_AB

Correct Answer: γ_SL

Q22. A surfactant that increases wetting and spreading on skin is likely to have which property?

  • High HLB (hydrophilic-lipophilic balance) value promoting surface activity
  • Very low molecular weight solids
  • High degree of crystallinity
  • No tendency to adsorb at interfaces

Correct Answer: High HLB (hydrophilic-lipophilic balance) value promoting surface activity

Q23. Which phenomenon can limit spreading even when S is slightly positive due to pinning by surface defects?

  • Contact angle hysteresis and surface heterogeneity
  • Complete miscibility of phases
  • Bulk phase chemical reaction
  • Optical interference

Correct Answer: Contact angle hysteresis and surface heterogeneity

Q24. Which of the following observations best indicates complete wetting on a solid surface?

  • Contact angle = 120°
  • Contact angle = 0° and film formation
  • Droplet remains spherical
  • Contact angle = 90°

Correct Answer: Contact angle = 0° and film formation

Q25. For a liquid-film spreading experiment, the presence of a precursor film is important because:

  • It blocks spreading entirely
  • It provides a thin molecular film that enhances propagation ahead of the macroscopic contact line
  • It increases bulk viscosity
  • It changes the surface charge only

Correct Answer: It provides a thin molecular film that enhances propagation ahead of the macroscopic contact line

Q26. In the context of pulmonary drug delivery, why is spreading important for aerosolized formulations deposited on mucosa?

  • Spreading determines dissolution and absorption on mucosal surfaces
  • Spreading prevents any drug absorption
  • Spreading only affects color of deposit
  • Spreading converts drug into gas

Correct Answer: Spreading determines dissolution and absorption on mucosal surfaces

Q27. Which parameter is most useful to characterize wetting kinetics rather than equilibrium spreading coefficient?

  • Dynamic contact angle and spreading rate
  • Bulk density
  • pKa of the drug
  • Thermal conductivity

Correct Answer: Dynamic contact angle and spreading rate

Q28. A spreading coefficient of -15 mN/m suggests which behavior?

  • Spontaneous complete spreading
  • Partial wetting; droplet with finite contact angle
  • Complete non-wetting and immediate recoil
  • Instant chemical reaction

Correct Answer: Partial wetting; droplet with finite contact angle

Q29. Which surface treatment would most likely increase spreading of a formulation on a plastic substrate?

  • Plasma treatment to increase surface energy
  • Applying a hydrophobic coating
  • Increasing ambient humidity only
  • Polishing to make it more hydrophobic

Correct Answer: Plasma treatment to increase surface energy

Q30. Which equation relates interfacial tensions and equilibrium contact angle for a perfectly smooth, homogeneous solid?

  • Szyszkowski equation
  • Young’s equation
  • Henderson–Hasselbalch equation
  • Arrhenius equation

Correct Answer: Young’s equation

Q31. Which of the following best describes partial wetting?

  • Sufficiently large positive S so film spreads indefinitely
  • Negative or small S leading to a finite contact angle
  • No interface exists between phases
  • Liquid instantly evaporates

Correct Answer: Negative or small S leading to a finite contact angle

Q32. Which factor can cause dynamic spreading to be slower than predicted by equilibrium S value?

  • Viscous dissipation in the moving liquid
  • Increased gravitational constant
  • Rapid chemical equilibrium
  • Absence of surface tension

Correct Answer: Viscous dissipation in the moving liquid

Q33. In calculation of S, units of surface/interfacial tension are commonly expressed as:

  • mN/m or dyn/cm
  • mg/mL
  • mol/L
  • °C

Correct Answer: mN/m or dyn/cm

Q34. Which pharmaceutical process directly benefits from improved spreading of coating solutions?

  • Capsule filling
  • Tablet film coating uniformity and coverage
  • Lyophilization
  • Granulation by dry mixing only

Correct Answer: Tablet film coating uniformity and coverage

Q35. A liquid with a contact angle of 150° on a solid is classified as:

  • Highly wetting
  • Partially wetting
  • Non-wetting (hydrophobic)
  • Completely spreading

Correct Answer: Non-wetting (hydrophobic)

Q36. If a cosθ value is 0.8 and γ_L = 25 mN/m, what is S?

  • S = 20 mN/m
  • S = -5 mN/m
  • S = 5 mN/m
  • S = -20 mN/m

Correct Answer: S = -5 mN/m

Q37. Which surface characteristic of a solid tends to enhance apparent wetting even if chemical surface energy is low?

  • High surface roughness that promotes wetting (Wenzel state)
  • High smoothness always prevents wetting
  • Increased bulk porosity only
  • Low thermal conductivity

Correct Answer: High surface roughness that promotes wetting (Wenzel state)

Q38. For a three-phase system solid (S), liquid (L) and vapor (V), what does γ_S represent?

  • Interfacial tension between liquid and vapor
  • Surface free energy of solid in contact with vapor
  • Viscosity of the solid
  • Bulk modulus of the liquid

Correct Answer: Surface free energy of solid in contact with vapor

Q39. What is the likely effect of adding an oil phase with very low γ_L to an aqueous film on skin?

  • Reduced spreading of the mixed formulation on skin
  • Enhanced spreading and potential increase in skin coverage
  • No change in spreading behavior
  • Immediate solidification on contact

Correct Answer: Enhanced spreading and potential increase in skin coverage

Q40. Which descriptor explains the ability of a liquid to wet a powder surface during granulation?

  • Spreading coefficient and contact angle on powder particles
  • Only pH matters for wetting
  • Bulk density exclusively determines wetting
  • Viscosity has no role during wetting

Correct Answer: Spreading coefficient and contact angle on powder particles

Q41. Which is true for a liquid film that exhibits negative spreading coefficient but still spreads slowly over time?

  • Impossible—negative S always prevents any spreading
  • Slow spreading may occur due to surfactant adsorption reducing γ_L dynamically
  • Only gravity can cause this spreading
  • It means measurement was done incorrectly every time

Correct Answer: Slow spreading may occur due to surfactant adsorption reducing γ_L dynamically

Q42. What role does adsorption kinetics of surfactant molecules play in spreading?

  • No role; adsorption is instantaneous
  • Slow adsorption can delay lowering γ_L and retard spreading initially
  • Adsorption kinetics only affect color of solution
  • Adsorption always prevents spreading

Correct Answer: Slow adsorption can delay lowering γ_L and retard spreading initially

Q43. Which term describes spreading driven by molecular interactions forming a precursor monolayer ahead of the macroscopic contact line?

  • Hydrodynamic spreading
  • Precursor film spreading or molecular precursor wetting
  • Bulk convection
  • Ostwald ripening

Correct Answer: Precursor film spreading or molecular precursor wetting

Q44. When designing topical gels, controlling spreading helps to:

  • Ensure uniform active distribution and controlled dose per area
  • Increase tablet hardness
  • Change chemical identity of the drug
  • Prevent any contact with skin

Correct Answer: Ensure uniform active distribution and controlled dose per area

Q45. Which of the following indicates poor wetting during coating processes?

  • Continuous uniform film
  • Beading or dewetting of the coating solution
  • Complete absorption into substrate
  • Zero contact angle

Correct Answer: Beading or dewetting of the coating solution

Q46. In a numerical problem, if γ_B = 30 mN/m, γ_A = 20 mN/m and γ_AB = 5 mN/m for liquid A on liquid B, what is S?

  • S = 5 mN/m
  • S = 15 mN/m
  • S = -5 mN/m
  • S = 0 mN/m

Correct Answer: S = 5 mN/m

Q47. Which phenomenon can counteract spreading even when surface energies favor it, due to solutal Marangoni stresses?

  • Uniform concentration everywhere
  • Surface tension gradients causing inward flows that resist spreading
  • Complete evaporation only
  • Perfect molecular miscibility suddenly appearing

Correct Answer: Surface tension gradients causing inward flows that resist spreading

Q48. Which property of a polymeric coating solution might reduce its spreading compared to a low-viscosity solvent?

  • Higher viscosity leading to slower spreading kinetics
  • Lower molecular weight always increases spreading
  • Higher volatility increases spread
  • Presence of more water molecules increases spreading instantly

Correct Answer: Higher viscosity leading to slower spreading kinetics

Q49. Which of the following best describes “autophobic” behavior related to spreading?

  • A liquid spreads easily on a substrate coated by the same liquid
  • A liquid does not wet a layer of itself previously deposited due to surface phase behavior
  • Complete miscibility between phases
  • Instant gelation upon contact

Correct Answer: A liquid does not wet a layer of itself previously deposited due to surface phase behavior

Q50. When formulating an oral suspension, why is knowledge of spreading and wetting important for suspension stability?

  • Wetting determines how drug particles are wetted by the vehicle, influencing dispersion and aggregation
  • Wetting only affects taste but not stability
  • Spreading has no impact on particle–vehicle interactions
  • Only chemical compatibility matters, not wetting

Correct Answer: Wetting determines how drug particles are wetted by the vehicle, influencing dispersion and aggregation

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