Powders – definition, classification, advantages and disadvantages MCQs With Answer

Introduction: Powders are dry, bulk solids composed of numerous finely divided particles and form a fundamental dosage form in pharmaceutics. This topic covers powder definition, classification (e.g., bulk, divided, dusting, effervescent, inhalation), particle size and specific surface area, flow properties, packing and porosity, and formulation principles such as blending, granulation, and use of excipients (lubricants, glidants, disintegrants). You will also learn quality control tests (angle of repose, bulk/tapped density, Carr’s index, Hausner ratio), advantages (dose flexibility, rapid dissolution) and disadvantages (segregation, poor dose uniformity, moisture sensitivity). Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the standard pharmaceutical definition of a powder?

• A mixture of liquid droplets suspended in air
• A dry, bulk solid composed of a large number of very fine particles
• A semi-solid mass that flows under pressure
• A gaseous dispersion of active drug particles

Correct Answer: A dry, bulk solid composed of a large number of very fine particles

Q2. Which classification refers to powders packaged for dispensing in measured quantities for a patient?

• Bulk powders
• Divided powders (chartulae)
• Effervescent powders
• Insufflations

Correct Answer: Divided powders (chartulae)

Q3. Which powder type is intended to be applied externally to the skin to reduce moisture or friction?

• Effervescent powder
• Dusting powder
• Dry powder for inhalation
• Buffered powder

Correct Answer: Dusting powder

Q4. How does reducing particle size generally affect dissolution rate of a poorly soluble drug in a powder formulation?

• Decreases dissolution due to increased aggregation
• Has no effect on dissolution
• Increases dissolution by increasing specific surface area
• Prevents wetting and slows dissolution

Correct Answer: Increases dissolution by increasing specific surface area

Q5. Which simple test is commonly used to evaluate the flow property of a powder?

• pH measurement
• Angle of repose
• Loss on drying
• Hygroscopicity index

Correct Answer: Angle of repose

Q6. Carr’s compressibility index is derived from which two measured densities?

• True density and particle density
• Bulk density and tapped density
• Apparent density and skeletal density
• Porosity and specific gravity

Correct Answer: Bulk density and tapped density

Q7. The Hausner ratio is defined as which of the following?

• Bulk density divided by tapped density
• Tapped density divided by bulk density
• True density divided by bulk density
• Apparent density divided by true density

Correct Answer: Tapped density divided by bulk density

Q8. Which Carr’s index value range indicates excellent flow properties?

• Greater than 30%
• 20–30%
• 15–20%
• Less than 10–15%

Correct Answer: Less than 10–15%

Q9. Which milling method is most suitable for producing very fine (submicron to micron) drug particles without excessive heat?

• Hammer milling
• Ball milling
• Jet milling (air milling)
• Mortar and pestle

Correct Answer: Jet milling (air milling)

Q10. Spray drying as a powder production technique is particularly useful for:

• Producing large granules for tablets
• Converting liquids into uniform, controlled particle-size dry powders
• Reducing bulk density by mechanical compression
• Forming coherent molten masses

Correct Answer: Converting liquids into uniform, controlled particle-size dry powders

Q11. The primary objectives of granulation in powder processing are:

• Increase drug melting point and change chemical identity
• Improve flow and compressibility for tableting or capsule filling
• Increase hygroscopicity and make powder sticky
• Separate API from excipients

Correct Answer: Improve flow and compressibility for tableting or capsule filling

Q12. Which excipient is commonly used as a glidant to improve powder flow?

• Magnesium stearate
• Microcrystalline cellulose
• Colloidal silicon dioxide (Aerosil)
• Sodium chloride

Correct Answer: Colloidal silicon dioxide (Aerosil)

Q13. A major disadvantage of powder dosage forms is:

• Inability to tailor dose
• High mechanical strength compared to tablets
• Risk of segregation leading to dose non-uniformity
• Longer dissolution compared to compressed tablets

Correct Answer: Risk of segregation leading to dose non-uniformity

Q14. Which of the following best describes the aerodynamic particle size range ideal for deep lung deposition for dry powder inhalers?

• 10–50 µm
• 5–10 µm
• 1–5 µm
• 0.01–0.1 µm

Correct Answer: 1–5 µm

Q15. Which quality control parameter is directly measured by repeatedly tapping a graduated cylinder containing the powder?

• True density
• Bulk viscosity
• Tapped density
• Moisture content

Correct Answer: Tapped density

Q16. Which combination of powder properties most promotes segregation during handling?

• Uniform particle size and identical density
• Wide particle size distribution and significant density differences
• High cohesion and strong electrostatic charge
• High moisture content with perfect mixing

Correct Answer: Wide particle size distribution and significant density differences

Q17. Which test provides information about powder wettability and tendency to be dispersed in a liquid?

• Angle of repose
• Wettability or wetting time test
• Tap density only
• pH of the powder

Correct Answer: Wettability or wetting time test

Q18. Effervescent powders typically contain which acid–base pair to release carbon dioxide on contact with water?

• Citric acid and sodium bicarbonate
• Hydrochloric acid and sodium hydroxide
• Sulfuric acid and calcium carbonate
• Acetic acid and potassium carbonate

Correct Answer: Citric acid and sodium bicarbonate

Q19. Which material is commonly used as a lubricant in powder formulations to reduce die wall adhesion during tableting?

• Colloidal silicon dioxide
• Magnesium stearate
• Lactose monohydrate
• Hydroxypropyl cellulose

Correct Answer: Magnesium stearate

Q20. Which particle-sizing technique gives a rapid distribution of particle sizes including volume-based data suitable for powders?

• Sieve analysis only
• Laser diffraction
• Thermal gravimetric analysis
• High-performance liquid chromatography

Correct Answer: Laser diffraction

Q21. Which physical phenomenon causes caking of powders during storage?

• Excessive particle hardness
• Moisture sorption and formation of solid bridges between particles
• Low bulk density only
• Excessive airflow through packaging

Correct Answer: Moisture sorption and formation of solid bridges between particles

Q22. What is the expected angle of repose for a powder exhibiting excellent flow?

• Greater than 50°
• Between 40° and 50°
• About 35°
• Less than 30°

Correct Answer: Less than 30°

Q23. Which process is most appropriate to reduce the cohesive tendency of a fine powder and improve flowability?

• Add a suitable glidant like colloidal silica
• Increase hygroscopic content intentionally
• Store powder at high relative humidity
• Decrease particle size further by micronization

Correct Answer: Add a suitable glidant like colloidal silica

Q24. Which packaging property is most critical for moisture-sensitive powders?

• Light transmittance only
• Moisture barrier/impermeability
• Ability to absorb moisture
• Rigid material irrespective of seal

Correct Answer: Moisture barrier/impermeability

Q25. For good content uniformity in low-dose potent powders, which approach is commonly used?

• Use only dry blending without any size reduction
• Use ordered mixing with carrier particles or use granulation
• Rely on gravity segregation during filling
• Increase particle size disparity to aid mixing

Correct Answer: Use ordered mixing with carrier particles or use granulation

Q26. Which analytical method is used to determine the specific surface area of powders by gas adsorption?

• Laser diffraction
• BET (Brunauer–Emmett–Teller) method
• pH titration
• Surface tension measurement

Correct Answer: BET (Brunauer–Emmett–Teller) method

Q27. Dry powder inhaler formulations often include lactose for what main purpose?

• Lactose acts as a preservative preventing microbial growth
• Lactose serves as an inert carrier to aid dose metering and dispersion
• Lactose increases particle cohesion to reduce aerosolization
• Lactose is used as a lubricant for inhaler mechanisms only

Correct Answer: Lactose serves as an inert carrier to aid dose metering and dispersion

Q28. Which factor most directly affects aerosol performance and deposition of dry powder inhalation products?

• Tablet hardness
• Aerodynamic particle size distribution
• Bulk color of the powder
• Container shape only

Correct Answer: Aerodynamic particle size distribution

Q29. Which storage condition is generally recommended to minimize degradation and caking of hygroscopic powders?

• High temperature and high humidity
• Low temperature with high humidity
• Cool, dry, and well-sealed conditions
• Open-air shelves to promote drying

Correct Answer: Cool, dry, and well-sealed conditions

Q30. Which safety hazard is particularly associated with handling large quantities of fine combustible pharmaceutical powders?

• Laser radiation hazard
• Dust explosion and fire risk
• Excessive microbial contamination only
• Instant chemical neutralization

Correct Answer: Dust explosion and fire risk

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