Amorphous solids MCQs With Answer

Amorphous solids MCQs With Answer are essential for B. Pharm students aiming to master solid-state pharmaceutics. This concise, SEO-friendly introduction covers key concepts such as glass transition temperature (Tg), molecular mobility, physical stability, crystallization, dissolution enhancement, and analytical techniques like DSC, XRD and FTIR. Understanding preparation methods (spray drying, hot melt extrusion, lyophilization), the role of polymers and stabilizers, and factors affecting storage and bioavailability will strengthen exam performance and practical formulation skills. Practical MCQs help link theory to real-world drug design and stability assessment. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What defines an amorphous solid in pharmaceutics?

• Lack of long-range molecular order
• Presence of a crystalline lattice
• Single, sharp melting point
• High degree of periodicity

Correct Answer: Lack of long-range molecular order

Q2. Which technique is most commonly used to detect crystallinity in an amorphous sample?

• Differential Scanning Calorimetry (DSC)
• High-Performance Liquid Chromatography (HPLC)
• Ultraviolet Spectroscopy (UV)
• Gas Chromatography (GC)

Correct Answer: Differential Scanning Calorimetry (DSC)

Q3. Glass transition temperature (Tg) refers to:

• The temperature where a crystalline solid melts
• The temperature where amorphous material transitions from glassy to rubbery state
• The decomposition temperature of a polymer
• The temperature of maximum solubility

Correct Answer: The temperature where amorphous material transitions from glassy to rubbery state

Q4. Which property is typically higher in amorphous solids compared to crystalline forms?

• Thermodynamic stability
• Bulk density
• Saturation solubility
• Melting point

Correct Answer: Saturation solubility

Q5. A common signature of amorphous material in X-ray powder diffraction (XRPD) is:

• Sharp Bragg peaks
• Single crystal reflections
• Diffuse halo pattern
• Discrete lattice lines

Correct Answer: Diffuse halo pattern

Q6. Which of the following increases physical stability of an amorphous drug?

• Storage above Tg
• High molecular mobility
• Use of polymeric stabilizers that raise Tg
• High moisture content

Correct Answer: Use of polymeric stabilizers that raise Tg

Q7. The primary reason amorphous solids often have improved dissolution rates is:

• Higher crystallinity
• Lower surface area
• Higher free energy and molecular disorder
• Lower chemical potential

Correct Answer: Higher free energy and molecular disorder

Q8. Which method is widely used to prepare amorphous solids by rapid solvent removal?

• Cold compression
• Spray drying
• Slow cooling from melt
• Recrystallization

Correct Answer: Spray drying

Q9. What role do polymers like PVP and HPMC play in amorphous formulations?

• Act as crystallization promoters
• Increase molecular mobility
• Serve as stabilizers by inhibiting recrystallization
• Lower Tg and destabilize the system

Correct Answer: Serve as stabilizers by inhibiting recrystallization

Q10. In DSC thermograms of an amorphous drug, one typically observes:

• A sharp endothermic melting peak only
• A glass transition step and possibly an exothermic recrystallization peak
• Multiple sharp exothermic crystallization peaks exclusively
• No thermal events at all

Correct Answer: A glass transition step and possibly an exothermic recrystallization peak

Q11. Which factor most accelerates devitrification (recrystallization) of an amorphous drug?

• Storage well below Tg
• Presence of moisture acting as a plasticizer
• Strong drug–polymer interactions
• Use of antiplasticizers

Correct Answer: Presence of moisture acting as a plasticizer

Q12. The term “co-amorphous” refers to:

• A single-component crystalline drug form
• A mixture of two or more crystalline APIs
• An amorphous mixture of drug and low molecular weight co-former
• A hydrated crystalline salt

Correct Answer: An amorphous mixture of drug and low molecular weight co-former

Q13. Which analytical tool provides molecular-level information about hydrogen bonding in amorphous solids?

• XRPD
• Infrared spectroscopy (FTIR)
• Thermogravimetric analysis (TGA)
• Polarimetry

Correct Answer: Infrared spectroscopy (FTIR)

Q14. What does a higher fragility index indicate about an amorphous material?

• It behaves as a strong glass former with gradual viscosity change
• It manifests near-Arrhenius behavior
• It shows rapid change in dynamics near Tg (fragile glass)
• It cannot form glasses

Correct Answer: It shows rapid change in dynamics near Tg (fragile glass)

Q15. Which of the following is a primary advantage of amorphous solid dispersions (ASDs) in oral drug delivery?

• Decreased apparent solubility
• Enhanced dissolution and potential bioavailability
• Guaranteed long-term physical stability
• Reduced rate of absorption

Correct Answer: Enhanced dissolution and potential bioavailability

Q16. Hot melt extrusion (HME) is used to:

• Form crystalline salts only
• Prepare amorphous dispersions by melting drug with polymer
• Perform recrystallization under mild conditions
• Analyze thermal degradation exclusively

Correct Answer: Prepare amorphous dispersions by melting drug with polymer

Q17. Which statement about moisture sorption is correct for amorphous solids?

• Water always increases Tg
• Moisture can plasticize and lower Tg, promoting crystallization
• Amorphous solids are unaffected by humidity
• Moisture reduces molecular mobility

Correct Answer: Moisture can plasticize and lower Tg, promoting crystallization

Q18. Which parameter from DSC is used to estimate physical stability against crystallization?

• Onset of melting temperature only
• Glass transition temperature (Tg) and difference between storage temperature and Tg
• Boiling point
• Heat capacity of crystalline form only

Correct Answer: Glass transition temperature (Tg) and difference between storage temperature and Tg

Q19. The Kauzmann paradox concerns:

• Excess entropy of supercooled liquid approaching that of the crystal at low temperature
• The melting point of ionic salts
• Solubility limits in water
• Viscosity of molten metals

Correct Answer: Excess entropy of supercooled liquid approaching that of the crystal at low temperature

Q20. What is the effect of adding an antiplasticizer to an amorphous formulation?

• Lowering Tg and increasing mobility
• Increasing Tg and reducing molecular mobility
• Promoting hydration and plasticization
• Inducing immediate crystallization

Correct Answer: Increasing Tg and reducing molecular mobility

Q21. Which experimental observation indicates physical aging in an amorphous sample?

• Decrease in density with time at constant temperature
• Shift of Tg to higher temperatures and enthalpy relaxation
• Immediate recrystallization upon cooling
• Increase in solubility with storage

Correct Answer: Shift of Tg to higher temperatures and enthalpy relaxation

Q22. Which technique can monitor molecular mobility or relaxation times in amorphous solids?

• Nuclear Magnetic Resonance (NMR) relaxation studies
• UV-visible spectrophotometry
• Potentiometry
• Size-exclusion chromatography

Correct Answer: Nuclear Magnetic Resonance (NMR) relaxation studies

Q23. Co-amorphous systems are often designed to:

• Promote phase separation quickly
• Increase crystallization tendency
• Provide mutual stabilization between drug and co-former
• Reduce dissolution rates

Correct Answer: Provide mutual stabilization between drug and co-former

Q24. Which of the following best describes ‘recrystallization’ in amorphous pharmaceuticals?

• Transformation from amorphous to crystalline form, often reducing solubility
• Conversion of crystal to amorphous state
• Permanent chemical degradation of API
• Formation of amorphous hydrates only

Correct Answer: Transformation from amorphous to crystalline form, often reducing solubility

Q25. Which storage condition is generally recommended to minimize amorphous drug recrystallization?

• High temperature and high relative humidity
• Below Tg and low humidity
• Storage at Tg exactly
• Constant freeze-thaw cycles

Correct Answer: Below Tg and low humidity

Q26. The term “enthalpy relaxation” refers to:

• Immediate melting of crystalline impurities
• Slow structural relaxation of an amorphous material toward equilibrium, observable in DSC
• Rapid chemical degradation producing heat
• Loss of water from a hydrate

Correct Answer: Slow structural relaxation of an amorphous material toward equilibrium, observable in DSC

Q27. Which of the following favors glass formation during cooling of a melt?

• Slow cooling rate
• High molecular mobility and long time at nucleation-prone temperatures
• Rapid cooling (quenching) to avoid crystallization
• Presence of crystalline seeds

Correct Answer: Rapid cooling (quenching) to avoid crystallization

Q28. Which of these statements about amorphous salts is true?

• They always have lower solubility than their crystalline counterparts
• Salt formation cannot occur in amorphous form
• Amorphous salts can combine ionic interactions with high apparent solubility
• They are always chemically unstable

Correct Answer: Amorphous salts can combine ionic interactions with high apparent solubility

Q29. Which analytical method quantifies weight loss due to moisture or decomposition in amorphous samples?

• Thermogravimetric analysis (TGA)
• ATR-FTIR
• Dynamic Light Scattering (DLS)
• XRPD

Correct Answer: Thermogravimetric analysis (TGA)

Q30. Which phenomenon describes the increased molecular mobility near surfaces of amorphous particles?

• Surface crystallization resistance
• Enhanced surface mobility or surface relaxation
• Complete immobilization of chains at surface
• Surface polymerization

Correct Answer: Enhanced surface mobility or surface relaxation

Q31. In a ternary amorphous solid dispersion (drug, polymer, surfactant), surfactants typically:

• Always prevent recrystallization indefinitely
• May improve wettability and dissolution but can influence stability variably
• Reduce dissolution rate markedly
• Increase crystallization tendency only

Correct Answer: May improve wettability and dissolution but can influence stability variably

Q32. The term ‘glass forming ability’ (GFA) refers to:

• Probability that a compound will readily crystallize on cooling
• Capacity of a substance to form a glass upon cooling from the melt
• Solubility in water
• Chemical reactivity with polymers

Correct Answer: Capacity of a substance to form a glass upon cooling from the melt

Q33. Which of the following is an indicator of molecular level miscibility in amorphous dispersions?

• Presence of multiple distinct Tg values corresponding to each component
• Single, composition-dependent Tg indicating a homogeneous phase
• Immediate phase separation visible under light microscopy only
• Complete immiscibility at all temperatures

Correct Answer: Single, composition-dependent Tg indicating a homogeneous phase

Q34. Which process is most likely to produce residual solvent in an amorphous product?

• Spray drying with inadequate drying
• Complete melting under vacuum
• Dry milling under desiccation
• Storage in a dry inert atmosphere

Correct Answer: Spray drying with inadequate drying

Q35. Raman spectroscopy in amorphous solids is particularly useful to:

• Measure thermal weight loss
• Probe molecular conformations and detect crystalline signatures
• Directly measure Tg in bulk samples
• Determine bulk density

Correct Answer: Probe molecular conformations and detect crystalline signatures

Q36. Why are amorphous forms often considered metastable?

• They are at global thermodynamic minimum
• They have higher free energy than crystalline forms and may transform over time
• They cannot convert to any other solid form
• They are chemically inert

Correct Answer: They have higher free energy than crystalline forms and may transform over time

Q37. Which parameter is most directly related to the tendency of an amorphous drug to recrystallize during dissolution?

• The API’s melting point only
• The difference between the amorphous solubility and concentration achieved in solution (supersaturation level)
• Particle color
• API’s molecular weight only

Correct Answer: The difference between the amorphous solubility and concentration achieved in solution (supersaturation level)

Q38. Which of the following is a benefit of using polymeric carriers in amorphous solid dispersions?

• They guarantee chemical stability of API
• They can inhibit nucleation and crystal growth by intermolecular interactions
• They always decrease dissolution rate
• They transform polymers into crystalline state

Correct Answer: They can inhibit nucleation and crystal growth by intermolecular interactions

Q39. What is the main risk when scale-up spray drying for producing amorphous dispersions?

• Improved residual solvent removal at large scale
• Reproducibility of particle morphology, residual solvent, and amorphous content
• Guaranteed identical batch-to-batch Tg
• Elimination of crystallization risks

Correct Answer: Reproducibility of particle morphology, residual solvent, and amorphous content

Q40. Which of the following best describes “spinodal decomposition” in amorphous mixtures?

• Slow nucleation and growth of discrete crystals
• Spontaneous phase separation into compositionally different amorphous phases without nucleation barrier
• Immediate recrystallization into a single crystal
• Thermal degradation under inert atmosphere

Correct Answer: Spontaneous phase separation into compositionally different amorphous phases without nucleation barrier

Q41. Which of the following excipients is most commonly used as a hydrophilic polymeric stabilizer?

• Sodium chloride
• Polyvinylpyrrolidone (PVP)
• Calcium carbonate
• Magnesium stearate

Correct Answer: Polyvinylpyrrolidone (PVP)

Q42. Which term refers to the rate at which molecules rearrange in the amorphous state?

• Hydration rate
• Molecular mobility or relaxation time
• Crystalline growth constant only
• Diffusion coefficient in crystals only

Correct Answer: Molecular mobility or relaxation time

Q43. Which outcome is expected when an amorphous drug forms strong hydrogen bonds with a polymer?

• Increased tendency to crystallize
• Enhanced miscibility and potential stabilization against recrystallization
• Complete immiscibility and phase separation
• Immediate chemical reaction forming a new API

Correct Answer: Enhanced miscibility and potential stabilization against recrystallization

Q44. Which experimental condition would likely reduce the Tg of an amorphous formulation?

• Incorporation of an antiplasticizer
• Decreasing moisture content
• Exposure to humid environment increasing water content
• Blending with a high-Tg polymer

Correct Answer: Exposure to humid environment increasing water content

Q45. Why is monitoring residual crystallinity important in amorphous drug products?

• Residual crystals are irrelevant to performance
• Even small crystalline fractions can alter dissolution, stability, and bioavailability
• Crystallinity only affects color
• Crystals always improve solubility

Correct Answer: Even small crystalline fractions can alter dissolution, stability, and bioavailability

Q46. Which in vitro test helps predict in vivo supersaturation and precipitation behavior of an amorphous formulation?

• Compendial disintegration test only
• Dissolution testing under biorelevant conditions with supersaturation monitoring
• Melting point determination only
• pH titration without dissolution

Correct Answer: Dissolution testing under biorelevant conditions with supersaturation monitoring

Q47. UV-visible spectroscopy is useful in amorphous studies primarily to:

• Characterize crystallinity patterns
• Monitor solution concentration during dissolution and precipitation studies
• Measure Tg directly
• Determine residual solvent content

Correct Answer: Monitor solution concentration during dissolution and precipitation studies

Q48. Which approach can be used to deliberately reduce molecular mobility and improve stability?

• Increase storage temperature above Tg
• Add polymeric or low molecular weight antiplasticizers to raise Tg
• Introduce moisture to plasticize the system
• Maintain prolonged exposure to light

Correct Answer: Add polymeric or low molecular weight antiplasticizers to raise Tg

Q49. Which is a potential drawback of amorphous formulations despite improved solubility?

• Guaranteed chemical stability
• Increased risk of physical instability and recrystallization during storage or upon dissolution
• Lower bioavailability always
• No need for stabilization strategies

Correct Answer: Increased risk of physical instability and recrystallization during storage or upon dissolution

Q50. Which characterization technique can spatially map crystalline domains within an otherwise amorphous particle?

• Bulk DSC only
• Confocal Raman or mapping XRPD techniques
• Simple visual inspection
• UV spectroscopy without microscopy

Correct Answer: Confocal Raman or mapping XRPD techniques

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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