Derived properties of powders MCQs With Answer

Understanding the derived properties of powders is essential for B. Pharm students involved in formulation, processing, and quality control. Derived properties—such as particle size distribution, specific surface area, bulk and tapped density, porosity, angle of repose, flowability, compressibility, Hausner ratio and Carr’s index—influence mixing, granulation, tablet compression and capsule filling. Accurate measurement and interpretation using sieve analysis, BET, pycnometry and tapped density tests help predict segregation, compaction behavior and dissolution performance. Linking physico-mechanical powder characterization to dosage form design ensures robust formulation development and scale-up. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the Hausner ratio used to assess in pharmaceutical powders?

• Particle size distribution
• Flowability and compressibility
• Chemical stability
• Moisture content

Correct Answer: Flowability and compressibility

Q2. Which formula correctly defines Hausner ratio?

• Bulk density / Tapped density
• Tapped density / Bulk density
• True density / Bulk density
• Bulk density / True density

Correct Answer: Tapped density / Bulk density

Q3. Carr’s compressibility index is most directly calculated from which pair of measurements?

• Particle size and surface area
• Bulk density and tapped density
• Moisture content and angle of repose
• True density and bulk porosity

Correct Answer: Bulk density and tapped density

Q4. Which expression represents Carr’s index (compressibility)?

• (Tapped density − Bulk density) / Tapped density × 100
• (Tapped density − Bulk density) / Bulk density × 100
• (Bulk density − Tapped density) / Bulk density × 100
• (True density − Bulk density) / True density × 100

Correct Answer: (Tapped density − Bulk density) / Tapped density × 100

Q5. The angle of repose primarily provides information about a powder’s:

• Chemical reactivity
• Thermal stability
• Flowability and interparticle friction
• Moisture sorption isotherm

Correct Answer: Flowability and interparticle friction

Q6. Which of the following angle of repose values typically indicates excellent powder flow?

• Greater than 45°
• 30–40°
• 20–30°
• 40–50°

Correct Answer: 20–30°

Q7. Specific surface area of powders (m²/g) increases when particle size:

• Increases (becomes larger)
• Decreases (becomes finer)
• Remains constant regardless of size
• Is converted to spherical shapes only

Correct Answer: Decreases (becomes finer)

Q8. BET (Brunauer–Emmett–Teller) analysis measures which derived powder property?

• Porosity by mercury intrusion
• True density by gas pycnometry
• Specific surface area by gas adsorption
• Bulk density by tapping

Correct Answer: Specific surface area by gas adsorption

Q9. True (particle) density is best measured by which technique?

• Bulk density cylinder
• Tapped density tester
• Helium pycnometry
• Angle of repose funnel

Correct Answer: Helium pycnometry

Q10. Porosity (ε) of a powder bed can be estimated from which relationship?

• ε = 1 − (Bulk density / True density)
• ε = Bulk density × True density
• ε = (Tapped density / Bulk density) − 1
• ε = Angle of repose / 90°

Correct Answer: ε = 1 − (Bulk density / True density)

Q11. Which powder property most strongly affects tablet tensile strength during compression?

• Angle of repose alone
• Compressibility and compactibility
• Bulk color and odor
• BET surface area only

Correct Answer: Compressibility and compactibility

Q12. Sieve analysis yields which important derived parameter?

• D10, D50, D90 particle size distribution metrics
• True density of particles
• Specific heat capacity
• Moisture sorption kinetics

Correct Answer: D10, D50, D90 particle size distribution metrics

Q13. Which interparticulate force contributes most to cohesion in very fine pharmaceutical powders?

• Van der Waals forces
• Gravitational attraction
• Hydrodynamic drag
• Magnetic attraction

Correct Answer: Van der Waals forces

Q14. Addition of a glidant (e.g., colloidal silicon dioxide) to a formulation primarily:

• Increases chemical reactivity
• Enhances powder flow by reducing interparticle friction
• Raises true density significantly
• Promotes tablet disintegration

Correct Answer: Enhances powder flow by reducing interparticle friction

Q15. Which mechanism explains segregation of mixtures due to vibration and differences in particle size?

• Electrostatic attraction
• Sifting/percolation
• Ostwald ripening
• Capillary condensation

Correct Answer: Sifting/percolation

Q16. Tapped density measurement is used to estimate:

• Surface energy of particles
• Bulk packing and potential compressibility
• Chemical purity
• Melting point of excipients

Correct Answer: Bulk packing and potential compressibility

Q17. Which statement best distinguishes compressibility from compactibility?

• Compressibility is volume reduction; compactibility is ability to form a strong compact
• Compressibility measures chemical binding; compactibility measures color change
• Compressibility is independent of pressure; compactibility is pressure-dependent
• They are synonymous terms

Correct Answer: Compressibility is volume reduction; compactibility is ability to form a strong compact

Q18. Which powder property is most directly increased by surface roughness and porosity within particles?

• Angle of repose
• Specific surface area
• Brittleness
• Moisture content only

Correct Answer: Specific surface area

Q19. Which additive is more likely to reduce tablet tensile strength and hinder dissolution if overused?

• Colloidal silicon dioxide (glidant)
• Magnesium stearate (lubricant)
• Microcrystalline cellulose (binder/filler)
• Sodium starch glycolate (disintegrant)

Correct Answer: Magnesium stearate (lubricant)

Q20. A powder with Hausner ratio of 1.05 is expected to have:

• Poor flowability
• Very cohesive behavior
• Excellent flowability
• Extremely high porosity

Correct Answer: Excellent flowability

Q21. Which technique is appropriate to measure open (interparticulate) porosity of a powder bed?

• Mercury intrusion porosimetry for bed voids
• Helium pycnometry for closed porosity only
• UV spectroscopy
• Thermogravimetric analysis

Correct Answer: Mercury intrusion porosimetry for bed voids

Q22. When particle size distribution broadens (wider span), how does this typically affect packing?

• Packing density decreases due to uniform spheres
• Smaller particles can fill voids increasing packing density
• Packing becomes independent of size distribution
• Packing is governed only by moisture

Correct Answer: Smaller particles can fill voids increasing packing density

Q23. Which powder property assessment helps predict segregation during transport?

• Flowability and particle size distribution
• True density only
• Melting point and boiling point
• Color uniformity

Correct Answer: Flowability and particle size distribution

Q24. Capillary forces causing cohesion among particles are promoted by:

• Drying to zero moisture
• Small amounts of adsorbed moisture forming liquid bridges
• High-temperature sintering
• Decreasing relative humidity to 0%

Correct Answer: Small amounts of adsorbed moisture forming liquid bridges

Q25. Which is a practical method to improve flow of a cohesive powder during tablet manufacture?

• Reduce particle size further
• Add an appropriate glidant and adjust humidity
• Remove all lubricants
• Increase electrostatic charging intentionally

Correct Answer: Add an appropriate glidant and adjust humidity

Q26. In sieve analysis D50 (median diameter) means:

• 50% of particles by number are larger
• 50% of sample mass passes through a sieve of that opening and 50% is retained
• Diameter at which particles are perfectly spherical
• Particle size at 50 nm only

Correct Answer: 50% of sample mass passes through a sieve of that opening and 50% is retained

Q27. Electrostatic charges in powders usually increase when:

• Electrostatic dissipation is enhanced by humidity
• Fine dry particles are handled and rubbed against surfaces
• Particles are fully wetted with solvent
• Particles are sintered at high temperature

Correct Answer: Fine dry particles are handled and rubbed against surfaces

Q28. Which derived powder parameter directly influences dissolution rate of poorly soluble drugs in solid dosage forms?

• Specific surface area (higher increases dissolution)
• Angle of repose only
• Tapped density alone
• Color of powder

Correct Answer: Specific surface area (higher increases dissolution)

Q29. Interparticulate friction affecting flow is increased by which factor?

• Smoother particle surfaces
• Rounded particle shape
• Irregular shape and high surface roughness
• Presence of glidants

Correct Answer: Irregular shape and high surface roughness

Q30. Which combination of derived properties would most likely indicate a formulation risk for poor die filling and weight variability?

• Low Hausner ratio, high flowability, narrow PSD
• High Hausner ratio, poor flowability, broad PSD with fines
• High true density and low porosity only
• Very high specific surface area but excellent flow

Correct Answer: High Hausner ratio, poor flowability, broad PSD with fines