Porosity MCQs With Answer

Porosity MCQs With Answer provide B. Pharm students a focused review of pore structure and its influence on pharmaceutical powders, granules and solid dosage forms. This concise introduction covers key keywords such as porosity, open and closed pores, total porosity, pore size distribution, void volume, porosimetry, bulk density, true (particle) density, mercury intrusion, liquid displacement, BET surface area, and implications for tablet hardness, disintegration and drug release. Emphasis is placed on calculations, measurement techniques and practical effects during compaction and formulation. Clear, application-oriented questions will help reinforce theoretical understanding and laboratory skills. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the definition of porosity in pharmaceutical solids?

• Ratio of solid volume to pore volume
• Ratio of void volume to total volume (void volume/total volume)
• Mass of pores per unit mass of powder
• Surface area per unit mass

Correct Answer: Ratio of void volume to total volume (void volume/total volume)

Q2. Which formula correctly relates porosity (ε) to bulk density (ρb) and particle (true) density (ρp)?

• ε = ρb / ρp
• ε = ρp / ρb
• ε = 1 − (ρb / ρp)
• ε = 1 + (ρb / ρp)

Correct Answer: ε = 1 − (ρb / ρp)

Q3. What is the appropriate unit for porosity?

• g/cm3
• cm3/g
• Dimensionless (often expressed as %)
• m2/g

Correct Answer: Dimensionless (often expressed as %)

Q4. Which type of porosity allows continuous pathways for fluid flow and mass transfer?

• Closed porosity
• Isolated porosity
• Open porosity
• Surface porosity only

Correct Answer: Open porosity

Q5. Mercury intrusion porosimetry determines pore size distribution by which principle?

• Measuring liquid uptake over time
• Forcing mercury into pores under pressure to determine pore size distribution (mercury intrusion porosimetry)
• Counting pores visually on tablet surface
• Measuring electrical conductivity of pores

Correct Answer: Forcing mercury into pores under pressure to determine pore size distribution (mercury intrusion porosimetry)

Q6. Which non-wetting liquid is classically used in intrusion porosimetry for porosity analysis?

• Water
• Mercury
• Ethanol
• Glycerol

Correct Answer: Mercury

Q7. How does increased porosity generally affect tablet dissolution rate?

• Decreases dissolution due to lower surface area
• Increases dissolution by facilitating liquid penetration and wetting
• Has no effect on dissolution
• Always prevents drug release

Correct Answer: Increases dissolution by facilitating liquid penetration and wetting

Q8. What is the typical effect of higher porosity on tablet mechanical strength?

• Higher porosity increases tensile strength
• Higher porosity decreases mechanical strength
• Porosity does not influence strength
• Higher porosity always makes tablets elastic

Correct Answer: Higher porosity decreases mechanical strength

Q9. Which statement best defines open porosity?

• Volume of pores not connected to the surface
• Volume of interconnected pores communicating with the external surface
• Pores only visible under SEM
• Pores filled with bound water only

Correct Answer: Volume of interconnected pores communicating with the external surface

Q10. What are closed pores?

• Pores connected directly to the tablet surface
• Pores that are isolated and not connected to the external surface
• Pores filled only with air at atmospheric pressure
• Pores that always contain bound solvent

Correct Answer: Pores that are isolated and not connected to the external surface

Q11. If bulk density = 0.8 g/cm3 and particle density = 2.5 g/cm3, what is the porosity (%)?

• 32%
• 68%
• 20%
• 50%

Correct Answer: 68%

Q12. For a fixed particle density, how does increasing porosity affect bulk density?

• Bulk density increases
• Bulk density decreases
• Bulk density remains unchanged
• Bulk density becomes equal to particle density

Correct Answer: Bulk density decreases

Q13. The BET (Brunauer–Emmett–Teller) method primarily measures which property related to porosity?

• Pore tortuosity
• Specific surface area by gas adsorption (BET)
• Open pore volume at macropore scale only
• Tablet hardness

Correct Answer: Specific surface area by gas adsorption (BET)

Q14. Which technique is used to determine true (particle or skeletal) density of a powder accurately?

• Mercury intrusion porosimetry
• Helium pycnometry for true particle density
• Optical microscopy
• Tap density tester

Correct Answer: Helium pycnometry for true particle density

Q15. How does “void fraction” relate to porosity?

• Void fraction is unrelated to porosity
• Void fraction is the inverse of porosity
• They are synonymous terms
• Void fraction refers only to closed pores

Correct Answer: They are synonymous terms

Q16. According to IUPAC classification, which pore size ranges correspond to micro-, meso- and macropores?

• Micropores <2 nm; Mesopores 2–50 nm; Macropores >50 nm
• Micropores 2–50 nm; Mesopores <2 nm; Macropores >100 nm
• Micropores >50 nm; Mesopores 2–50 nm; Macropores <2 nm
• Micropores 10–100 nm; Mesopores 100–500 nm; Macropores >500 nm

Correct Answer: Micropores <2 nm; Mesopores 2–50 nm; Macropores >50 nm

Q17. What is the expected influence of increased porosity on tablet friability?

• Increased porosity decreases friability
• Increased porosity increases friability
• Porosity has no effect on friability
• Friability depends only on binder type, not porosity

Correct Answer: Increased porosity increases friability

Q18. How does porosity generally affect disintegration time of immediate-release tablets?

• Higher porosity usually prolongs disintegration time
• Higher porosity usually shortens disintegration time
• Porosity only affects dissolution, not disintegration
• Porosity effects are unpredictable and random

Correct Answer: Higher porosity usually shortens disintegration time

Q19. Which density excludes pore volume and represents true material density?

• Bulk density
• Apparent density
• Particle (true or skeletal) density
• Tapped density

Correct Answer: Particle (true or skeletal) density

Q20. What happens to porosity when compression pressure increases during tableting?

• Porosity increases with pressure
• Porosity decreases with increasing compression pressure
• Porosity remains constant regardless of pressure
• Porosity fluctuates unpredictably

Correct Answer: Porosity decreases with increasing compression pressure

Q21. A tablet weighs 0.9 g and occupies a volume of 1.0 cm3; particle density is 1.8 g/cm3. What is the porosity (%)?

• 25%
• 50%
• 60%
• 10%

Correct Answer: 50%

Q22. Which technique can measure a wide range of pore sizes including macropores and provide pore size distribution?

• Mercury intrusion porosimetry
• Optical density measurement
• Standard tablet friability tester
• pH titration

Correct Answer: Mercury intrusion porosimetry

Q23. How do closed pores influence permeability and diffusion in solid matrices?

• Closed pores enhance permeability by providing channels
• Closed pores do not contribute to continuous diffusion paths and reduce effective permeability
• Closed pores always increase diffusion rates
• Closed pores convert to open pores at ambient pressure

Correct Answer: Closed pores do not contribute to continuous diffusion paths and reduce effective permeability

Q24. Which statement correctly describes the relationship between porosity and permeability?

• High porosity always means high permeability
• Permeability depends on pore connectivity and size distribution as well as porosity
• Permeability is independent of pore connectivity
• Permeability depends only on solid density, not porosity

Correct Answer: Permeability depends on pore connectivity and size distribution as well as porosity

Q25. How is porosity (%) commonly calculated from void and total volume?

• Porosity (%) = (solid volume / total volume) × 100
• Porosity (%) = (void volume / total volume) × 100
• Porosity (%) = (total volume / void volume) × 100
• Porosity (%) = mass/volume × 100

Correct Answer: Porosity (%) = (void volume / total volume) × 100

Q26. Which imaging technique provides non-destructive 3D visualization and quantitative porosity analysis of tablets?

• Scanning electron microscopy (SEM) 2D surface imaging
• Mercury intrusion porosimetry
• X-ray micro-computed tomography (micro-CT) for 3D porosity mapping
• Optical light microscopy for cross-sections

Correct Answer: X-ray micro-computed tomography (micro-CT) for 3D porosity mapping

Q27. What does pore tortuosity describe?

• The straight-line distance between pores
• The ratio of actual path length for transport through pores to the straight-line distance
• The percentage of closed pores
• The diameter of the largest pore

Correct Answer: The ratio of actual path length for transport through pores to the straight-line distance

Q28. How does compressive force during tableting affect measured porosity in the final tablet?

• Compressive force increases measured porosity by creating voids
• Compressive force reduces porosity by collapsing interparticle voids
• Compressive force does not change porosity but changes color
• Compressive force only changes closed porosity, not open porosity

Correct Answer: Compressive force reduces porosity by collapsing interparticle voids

Q29. Carr’s compressibility index is based on bulk and tapped densities. What powder property related to porosity does it indirectly indicate?

• Surface chemistry of particles
• Powder flow and compressibility related to void volume and packing
• Moisture content only
• Particle crystallinity

Correct Answer: Powder flow and compressibility related to void volume and packing

Q30. In controlled-release matrix tablets, what is a common effect of higher initial porosity on drug release profile?

• Lower initial burst and slower release
• Higher initial burst release and faster early drug release
• No effect on release kinetics
• Immediate conversion to immediate-release behavior regardless of formulation

Correct Answer: Higher initial burst release and faster early drug release