Sublimation MCQs With Answer

Sublimation MCQs With Answer provide B.Pharm students a focused review of the solid-to-vapor transition, its thermodynamics, practical applications and analytical detection in pharmaceutics. This introduction covers key concepts such as direct solid-vapor conversion, triple point, vapor pressure, Clausius–Clapeyron relations, enthalpy of sublimation, vacuum sublimation and primary drying in lyophilization. Relevant pharmaceutical examples (camphor, menthol, naphthalene, iodine) and process controls for drug purification, drying and stability are emphasized. Mastery of these topics improves formulation design, packaging strategies and manufacturing troubleshooting. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is sublimation in the context of pharmaceutical solids?

• Transition from liquid to vapor
• Transition from solid directly to vapor without passing through liquid
• Transition from vapor to liquid
• Transition from liquid to solid

Correct Answer: Transition from solid directly to vapor without passing through liquid

Q2. Which of the following substances commonly shows sublimation at room temperature?

• Table salt (NaCl)
• Camphor
• Calcium carbonate
• Sucrose

Correct Answer: Camphor

Q3. The condition at which sublimation can occur is related to which property of the solid?

• Melting point only
• Vapor pressure of the solid
• Optical rotation
• Bulk density

Correct Answer: Vapor pressure of the solid

Q4. Which thermodynamic curve point marks the boundary where solid, liquid and gas coexist, relevant to sublimation behaviour?

• Critical point
• Triple point
• Melting point
• Boiling point

Correct Answer: Triple point

Q5. Which equation relates vapor pressure and temperature for sublimation processes?

• Nernst equation
• Clausius–Clapeyron equation
• Van’t Hoff equation
• Henderson–Hasselbalch equation

Correct Answer: Clausius–Clapeyron equation

Q6. Enthalpy of sublimation is best described as:

• Energy released when vapor becomes liquid
• Energy required to convert a solid directly into a vapor
• Energy required to melt a solid
• Energy released during crystallization

Correct Answer: Energy required to convert a solid directly into a vapor

Q7. In freeze-drying (lyophilization), the primary drying phase removes solvent by which mechanism?

• Evaporation of liquid water
• Sublimation of ice
• Condensation of vapor
• Melting of solutes

Correct Answer: Sublimation of ice

Q8. Which analytical technique directly measures mass loss due to sublimation with temperature?

• UV-Vis spectroscopy
• Thermogravimetric analysis (TGA)
• HPLC
• X-ray diffraction

Correct Answer: Thermogravimetric analysis (TGA)

Q9. Which of the following is NOT typically a factor that increases the sublimation rate of a pharmaceutical solid?

• Increased surface area
• Lower ambient pressure
• Higher temperature
• Applying a protective polymer coating

Correct Answer: Applying a protective polymer coating

Q10. Vacuum sublimation in pharmaceutical processing is mainly used to:

• Increase melting point
• Facilitate sublimation at lower temperatures for purification
• Cause crystallization from solution
• Increase solubility of drugs

Correct Answer: Facilitate sublimation at lower temperatures for purification

Q11. Which pharmaceutical compound is known for sublimation and is used as an example in formulations?

• Acetaminophen
• Iodine
• Aspirin
• Lactose

Correct Answer: Iodine

Q12. Sublimation can cause stability issues in stored solid dosage forms primarily because:

• It increases tablet hardness
• Active ingredients may be lost as vapor leading to potency loss
• It always causes chemical degradation
• It increases moisture uptake

Correct Answer: Active ingredients may be lost as vapor leading to potency loss

Q13. Which packaging strategy can reduce sublimation losses during storage?

• High-permeability packaging
• Using desiccants only
• Hermetic or barrier packaging with low vapor transmission
• Thin paper wraps

Correct Answer: Hermetic or barrier packaging with low vapor transmission

Q14. Deposition is the reverse process of sublimation and involves:

• Liquid turning into solid
• Vapor directly becoming solid
• Solid melting into liquid
• Liquid evaporating into gas

Correct Answer: Vapor directly becoming solid

Q15. Which physical parameter must equal ambient pressure for a solid to sublime at a given temperature?

• Solid density
• Vapor pressure of the solid
• Surface tension
• Dielectric constant

Correct Answer: Vapor pressure of the solid

Q16. How does particle size affect the sublimation rate of a drug powder?

• Larger particles sublimate faster due to mass
• Smaller particles sublimate faster due to higher surface area
• Particle size has no effect
• Only particle shape matters

Correct Answer: Smaller particles sublimate faster due to higher surface area

Q17. Which instrument can detect sublimated material deposits during a sublimation experiment?

• Cold trap followed by gravimetric analysis
• pH meter
• Conductivity meter
• Refractometer

Correct Answer: Cold trap followed by gravimetric analysis

Q18. The term “sublimation trap” in pharmaceutical labs refers to:

• A device to increase sublimation rate
• A condenser/cold surface to collect vapors
• A solvent reservoir
• A dissolution vessel

Correct Answer: A condenser/cold surface to collect vapors

Q19. Which of the following best describes why lowering pressure facilitates sublimation?

• It decreases molecular weight of solids
• It reduces the external pressure resisting vapor formation, allowing sublimation at lower temperatures
• It increases heat capacity
• It neutralizes surface charge

Correct Answer: It reduces the external pressure resisting vapor formation, allowing sublimation at lower temperatures

Q20. Which pharmaceutical process uses controlled sublimation to purify volatile solids?

• Recrystallization from solvent
• Vacuum sublimation
• Spray drying
• Granulation

Correct Answer: Vacuum sublimation

Q21. In Clausius–Clapeyron form, a plot of ln(pressure) versus 1/T yields a slope proportional to:

• Heat capacity
• Enthalpy of sublimation divided by R
• Viscosity
• Entropy of mixing

Correct Answer: Enthalpy of sublimation divided by R

Q22. Which statement about dry ice (solid CO2) is correct?

• It melts to liquid CO2 at atmospheric pressure
• It sublimates at atmospheric pressure
• It dissolves in water only
• It has a high boiling point

Correct Answer: It sublimates at atmospheric pressure

Q23. Which of these is a consequence of sublimation during tablet manufacturing?

• Improved dissolution uniformly
• Formation of voids or pores in tablets when volatile fillers sublimate
• Increased tablet mass
• Complete prevention of moisture uptake

Correct Answer: Formation of voids or pores in tablets when volatile fillers sublimate

Q24. Which compound used as a moth repellent is a classic example of sublimation?

• Naphthalene
• Ibuprofen
• Magnesium stearate
• Cellulose

Correct Answer: Naphthalene

Q25. Which parameter is most directly measured by Differential Scanning Calorimetry (DSC) that can relate to sublimation?

• Mass loss with temperature
• Heat flow associated with phase transitions
• Particle size distribution
• Surface area

Correct Answer: Heat flow associated with phase transitions

Q26. What role does protective coating play for a sublimating active ingredient in a solid dosage form?

• Increase sublimation rate
• Act as a barrier to reduce vapor loss
• Change the melting point dramatically
• Convert the solid into a gas

Correct Answer: Act as a barrier to reduce vapor loss

Q27. Which kinetic model is commonly considered when describing sublimation mass loss over time?

• Zero-order kinetics only
• Surface area dependent kinetics (often first-order or diffusion-controlled)
• Michaelis–Menten kinetics
• Langmuir adsorption kinetics exclusively

Correct Answer: Surface area dependent kinetics (often first-order or diffusion-controlled)

Q28. In an industrial vacuum sublimation setup, increasing the cold trap efficiency primarily does what?

• Raises processing temperature
• Improves recovery of sublimed material and protects vacuum pump
• Increases solution viscosity
• Destroys volatile compounds

Correct Answer: Improves recovery of sublimed material and protects vacuum pump

Q29. Which gas property influences the sublimation rate of a solid in a closed container?

• Color of the gas
• Partial pressure of the solid’s vapor in the headspace
• Electrical conductivity of the gas
• Solid’s refractive index

Correct Answer: Partial pressure of the solid’s vapor in the headspace

Q30. Which approach is effective to experimentally determine the enthalpy of sublimation?

• Measuring viscosity at one temperature
• Applying Clausius–Clapeyron to vapor pressure vs temperature data
• Using pH titration
• Colorimetric assay

Correct Answer: Applying Clausius–Clapeyron to vapor pressure vs temperature data

Q31. Why might a formulator prefer vacuum sublimation for purification over recrystallization for a volatile impurity?

• Vacuum sublimation works at higher temperatures than recrystallization
• It avoids solvents and can selectively remove volatile impurities
• It always yields larger crystals
• It increases solubility of impurities

Correct Answer: It avoids solvents and can selectively remove volatile impurities

Q32. Which of the following is a potential hazard when handling sublimating pharmaceutical solids?

• Formation of explosive peroxides
• Inhalation exposure to volatile active vapors
• Instant combustion upon handling
• Permanent magnetic contamination

Correct Answer: Inhalation exposure to volatile active vapors

Q33. In a sublimation purification, deposition occurs on a cooler surface because:

• Cooler surface increases vapor pressure
• Vapor molecules lose kinetic energy and deposit as solid
• Cooler surface chemically reacts with vapor
• Deposition is independent of temperature

Correct Answer: Vapor molecules lose kinetic energy and deposit as solid

Q34. Which formulation excipient might be chosen to reduce sublimation of a volatile drug by forming a solid dispersion?

• Volatile solvent
• Hydrophilic polymer like PVP
• Low-melting wax
• High-vapor-pressure salt

Correct Answer: Hydrophilic polymer like PVP

Q35. The sublimation point of a solid is best defined as the temperature at which:

• Solid and liquid coexist
• Vapor pressure of the solid equals the ambient pressure
• Solid becomes electrically conductive
• Molecular weight changes

Correct Answer: Vapor pressure of the solid equals the ambient pressure

Q36. What happens to the sublimation rate when a volatile solid is stored in a sealed container until equilibrium is reached?

• It accelerates indefinitely
• It decreases as the headspace vapor pressure builds and approaches equilibrium
• It becomes independent of temperature
• It causes immediate decomposition

Correct Answer: It decreases as the headspace vapor pressure builds and approaches equilibrium

Q37. Which of the following is a sign that sublimation has occurred on a solid dosage form during storage?

• Increase in tablet weight
• Visible deposition or crystalline patching on interior packaging faces
• Lower dissolution rate due to swelling
• Complete dissolution

Correct Answer: Visible deposition or crystalline patching on interior packaging faces

Q38. Which method can be used to quantify the amount of active lost to sublimation from a sample?

• Chromatographic analysis of the cold-trap wash
• Visual inspection only
• Measuring pH change in the container
• Counting particles by microscopy

Correct Answer: Chromatographic analysis of the cold-trap wash

Q39. During lyophilization, rapid primary drying by excessive heat can cause which undesirable effect related to sublimation?

• Improved product stability always
• Collapse or melting of the frozen matrix due to exceeding collapse temperature
• Complete prevention of microbial growth
• Instant chemical sterilization

Correct Answer: Collapse or melting of the frozen matrix due to exceeding collapse temperature

Q40. Which physical change indicates a high vapor pressure solid that may sublime readily?

• Very high molecular weight
• Low melting point and observable vapor at moderate temperatures
• Complete insolubility in organic solvents
• Extremely high crystallinity only

Correct Answer: Low melting point and observable vapor at moderate temperatures

Q41. Which property of a volatile drug determines how readily it will sublimate at a given temperature?

• Partition coefficient only
• Its vapor pressure at that temperature
• Optical activity
• Atomic number

Correct Answer: Its vapor pressure at that temperature

Q42. Which of the following is an industrial application of sublimation in pharmaceuticals?

• Tablet coating by melting
• Purification of small volatile organic compounds by vacuum sublimation
• Encapsulation by spray congealing
• Solvent-mediated polymorph screening only

Correct Answer: Purification of small volatile organic compounds by vacuum sublimation

Q43. The presence of non-volatile impurities in a sample undergoing sublimation typically results in:

• All impurities sublimating together
• Residue remaining at the original sample site after sublimation
• Instant vaporization of impurities
• Complete conversion to gas

Correct Answer: Residue remaining at the original sample site after sublimation

Q44. How can the shelf-life prediction account for sublimation loss of a volatile active?

• Ignore vapor pressure entirely
• Incorporate headspace vapor pressure, packaging permeability and temperature dependence into stability models
• Assume linear degradation only
• Only measure moisture content

Correct Answer: Incorporate headspace vapor pressure, packaging permeability and temperature dependence into stability models

Q45. Which factor is LEAST likely to influence the sublimation behaviour of a crystalline drug?

• Crystal habit and defects
• Ambient atmospheric composition
• Color of the crystal when powdered
• Presence of adsorbed moisture

Correct Answer: Color of the crystal when powdered

Q46. In sublimation studies, a linear Clausius–Clapeyron plot indicates:

• Constant enthalpy of sublimation over the tested temperature range
• Variable molar mass
• Non-ideal mixing
• Presence of multiple decomposition reactions

Correct Answer: Constant enthalpy of sublimation over the tested temperature range

Q47. What is a common laboratory precaution to minimize sublimation losses during weighing of a volatile solid?

• Weighing at elevated room temperature
• Use of sealed weigh boats or a desiccator and minimize exposure time
• Expose to direct sunlight
• Grinding the sample aggressively

Correct Answer: Use of sealed weigh boats or a desiccator and minimize exposure time

Q48. Which chemical characteristic tends to correlate with a higher propensity to sublime?

• Very high polarity and ionic bonding
• Low molecular weight with relatively weak intermolecular forces
• High polymeric chain length
• Strong ionic lattice energy

Correct Answer: Low molecular weight with relatively weak intermolecular forces

Q49. What is a likely effect when a volatile active sublimes from a cream or ointment base?

• Increased viscosity of the base
• Loss of fragrance or therapeutic activity and possible change in appearance
• Immediate sterilization of the base
• Conversion of the base to a gel

Correct Answer: Loss of fragrance or therapeutic activity and possible change in appearance

Q50. Which control strategy is appropriate during lyophilization to prevent collapse due to excessive sublimation rate?

• Increase shelf temperature above collapse temperature
• Maintain product temperature below collapse temperature and control chamber pressure
• Remove cooling system
• Allow uncontrolled pressure rise

Correct Answer: Maintain product temperature below collapse temperature and control chamber pressure

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