Crystal Morphology & Powder Flow MCQs With Answer

Introduction

Crystal Morphology & Powder Flow MCQs With Answer is designed for M.Pharm students studying Pharmaceutical Formulation Development (MIP 102T). This set of multiple-choice questions focuses on how crystal shape, size, and surface properties influence powder behavior during processing and dosage form manufacture. Topics covered include crystal habit, polymorphism, packing, particle size distribution, surface energy, interparticle forces, and common flowability tests such as angle of repose, Carr’s index, and Hausner ratio. The questions emphasize practical implications for granulation, compression, and flow improvement strategies like glidants and granulation. Each question is followed by four options and the correct answer to help reinforce key concepts and exam preparation.

Q1. What is the primary distinction between crystal habit and crystal morphology?

• Crystal habit refers to internal lattice arrangement while crystal morphology refers to chemical composition
• Crystal habit is the external shape developed under given growth conditions; crystal morphology includes habit plus internal defects and surface features
• Crystal habit describes thermal behavior and crystal morphology describes solubility
• They are synonymous terms with identical meaning

Correct Answer: Crystal habit is the external shape developed under given growth conditions; crystal morphology includes habit plus internal defects and surface features

Q2. Which analytical technique gives the best direct visualization of particle surface texture and micro-morphology?

• Powder X-ray diffraction (PXRD)
• Scanning electron microscopy (SEM)
• Thermogravimetric analysis (TGA)
• Differential scanning calorimetry (DSC)

Correct Answer: Scanning electron microscopy (SEM)

Q3. Polymorphism in pharmaceuticals primarily affects which of the following properties?

• Only the color of the solid
• Solubility, dissolution rate, stability and mechanical properties
• Only the melting point with no impact on bioavailability
• Only the particle size distribution

Correct Answer: Solubility, dissolution rate, stability and mechanical properties

Q4. Hausner ratio is defined as which relationship between tapped density and bulk density?

• Bulk density divided by tapped density
• Tapped density divided by bulk density
• True density divided by bulk density
• Tapped density minus bulk density

Correct Answer: Tapped density divided by bulk density

Q5. Which value of angle of repose typically indicates excellent powder flow?

• Greater than 45 degrees
• Between 35 and 45 degrees
• Between 30 and 35 degrees
• Less than 30 degrees

Correct Answer: Less than 30 degrees

Q6. Carr’s compressibility index is most directly used to assess which powder attribute?

• Chemical stability
• Flowability and compressibility
• Thermal conductivity
• Optical clarity

Correct Answer: Flowability and compressibility

Q7. Which interparticle force becomes dominant in cohesive fine pharmaceutical powders under low humidity conditions?

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

Correct Answer: Van der Waals forces

Q8. The true density of a powder is most accurately measured by which instrument?

• Tapped density tester
• Gas pycnometer
• Optical microscope
• Laser diffraction particle size analyzer

Correct Answer: Gas pycnometer

Q9. Random close packing of equal spheres corresponds approximately to what solid volume fraction?

• 0.36
• 0.52
• 0.64
• 0.85

Correct Answer: 0.64

Q10. Which particle shape parameter is commonly used to quantify deviation from a perfect sphere?

• Aspect ratio
• Porosity
• True density
• Hardness

Correct Answer: Aspect ratio

Q11. Which formulation approach is most effective to improve flow of very fine cohesive powders?

• Reducing particle size further by micronization
• Adding a glidant or lubricant and/or granulation to enlarge particle size
• Increasing static charge intentionally
• Using freeze-drying to create more fluffy powder

Correct Answer: Adding a glidant or lubricant and/or granulation to enlarge particle size

Q12. Surface roughness of particles influences powder flow mainly by altering which property?

• Electrical conductivity
• Inter-particle contact area and mechanical interlocking
• Color and transparency
• Chemical reactivity

Correct Answer: Inter-particle contact area and mechanical interlocking

Q13. Which of the following is a direct consequence of high moisture content in a powder bed?

• Reduced capillary forces between particles
• Increased inter-particle cohesion due to liquid bridges
• Instant improvement in powder flow regardless of powder type
• Lower bulk density with no change in tapped density

Correct Answer: Increased inter-particle cohesion due to liquid bridges

Q14. Sphericity is best described as:

• The ratio of the volume of a particle to the volume of a cube enclosing it
• A measure of how closely the shape of a particle approaches that of a sphere
• The chemical purity of a crystalline particle
• The thermal expansion coefficient of a particle

Correct Answer: A measure of how closely the shape of a particle approaches that of a sphere

Q15. Which of the following powder tests is least influenced by sample packing and tapping?

• Tapped density measurement
• Angle of repose
• Bulk density after tapping
• Hausner ratio

Correct Answer: Angle of repose

Q16. A high Hausner ratio (>1.25) indicates what characteristic of a powder?

• Excellent flowability
• High cohesiveness and poor flow
• High moisture resistance
• Low particle size

Correct Answer: High cohesiveness and poor flow

Q17. Which crystal growth modifier is commonly used during crystallization to alter habit by selectively adsorbing on specific crystal faces?

• Inert gas
• Impurity or tailor-made additive (habit modifier)
• High temperature only
• Vacuum

Correct Answer: Impurity or tailor-made additive (habit modifier)

Q18. The primary reason needle-shaped crystals often cause processing problems is due to:

• Higher true density than other shapes
• Tendency to interlock and entangle causing poor flow and segregation
• Lower solubility than spherical crystals
• Magnetic interactions between needles

Correct Answer: Tendency to interlock and entangle causing poor flow and segregation

Q19. Which measurement provides information about the mechanical behavior of powder during compression?

• Dynamic vapor sorption
• Compaction profile from a tablet press (force-displacement curve)
• Optical clarity index
• Angle of contact with water

Correct Answer: Compaction profile from a tablet press (force-displacement curve)

Q20. In image analysis for particle characterization, Feret diameter primarily measures:

• The diameter of the largest inscribed circle within the particle
• The longest distance between any two points along the particle boundary (caliper diameter)
• The average height of surface roughness peaks
• The thermal diffusivity of the particle

Correct Answer: The longest distance between any two points along the particle boundary (caliper diameter)

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