Hygroscopic powders MCQs With Answer

Introduction: Hygroscopic Powders MCQs With Answer

Hygroscopic powders readily absorb moisture from the atmosphere, affecting flow, stability, caking, dissolution, and shelf-life. For B. Pharm students, understanding hygroscopicity, deliquescence, efflorescence, water activity, sorption isotherms, critical relative humidity (CRH), and controlled packaging is essential for preformulation, compounding, and industrial manufacturing. Key concepts include moisture uptake mechanisms (adsorption vs absorption), analytical methods (Karl Fischer, LOD, DVS), excipient selection (mannitol, lactose, colloidal silica), use of desiccants (silica gel, molecular sieves), and ICH stability conditions. Mastering mitigation strategies—dry granulation, hydrophobic coatings, glidants/anti-caking agents, and high-barrier packs (Alu-Alu)—ensures quality and performance. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What best defines a hygroscopic powder?

• A powder that loses water of crystallization to air at low humidity
• A powder that absorbs moisture from air but does not dissolve
• A powder that sublimes readily at room temperature
• A powder that dissolves spontaneously in any solvent

Correct Answer: A powder that absorbs moisture from air but does not dissolve

Q2. What distinguishes a deliquescent powder from a merely hygroscopic one?

• Deliquescent powders release water on standing
• Deliquescent powders absorb moisture until they form a solution
• Deliquescent powders are always crystalline hydrates
• Deliquescent powders do not change mass with humidity

Correct Answer: Deliquescent powders absorb moisture until they form a solution

Q3. Which term describes solids that lose water of crystallization to the atmosphere?

• Efflorescent
• Hygroscopic
• Deliquescent
• Desiccant

Correct Answer: Efflorescent

Q4. Moisture uptake by a hygroscopic powder is primarily driven by which gradient?

• Temperature gradient between powder and air
• Water activity gradient between material and environment
• Electrostatic potential difference
• Osmotic pressure of the powder bed

Correct Answer: Water activity gradient between material and environment

Q5. Which excipient is generally least hygroscopic and useful to dilute hygroscopic APIs?

• Sorbitol
• Lactose monohydrate
• Mannitol
• Sodium chloride

Correct Answer: Mannitol

Q6. Which salt is strongly deliquescent and often used as a drying agent?

• Calcium chloride
• Sodium chloride
• Potassium nitrate
• Magnesium sulfate heptahydrate

Correct Answer: Calcium chloride

Q7. Which method specifically quantifies water content (not other volatiles) in hygroscopic powders?

• Loss on drying (LOD) at 105 °C
• Karl Fischer titration
• Differential scanning calorimetry (DSC)
• Particle size analysis

Correct Answer: Karl Fischer titration

Q8. Which technique is best to generate moisture sorption/desorption isotherms and kinetics?

• Dynamic vapor sorption (DVS)
• Thin-layer chromatography (TLC)
• UV–Vis spectrophotometry
• Gas chromatography (GC)

Correct Answer: Dynamic vapor sorption (DVS)

Q9. As moisture content increases in a hygroscopic powder, which is most likely to occur?

• Improved flow and reduced caking
• No change in compressibility
• Increased caking and poorer flow
• Increased electrostatic charging

Correct Answer: Increased caking and poorer flow

Q10. How do angle of repose and Hausner ratio typically change as a powder absorbs moisture?

• Both decrease
• Angle decreases; Hausner increases
• Angle increases; Hausner increases
• Angle increases; Hausner decreases

Correct Answer: Angle increases; Hausner increases

Q11. Critical relative humidity (CRH) of a powder is best described as:

• RH below which the material burns
• RH above which rapid moisture uptake begins
• RH at which the material effloresces
• RH at which the material becomes amorphous

Correct Answer: RH above which rapid moisture uptake begins

Q12. Which packaging gives the highest moisture barrier for sensitive solid doses?

• PVC blister with paper lidding
• HDPE bottle with screw cap
• Alu-Alu blister
• Amber Type III soda-lime glass without desiccant

Correct Answer: Alu-Alu blister

Q13. Which desiccant is preferred when very low in-package RH (e.g., below 10%) is required?

• Silica gel
• Molecular sieve (zeolite)
• Montmorillonite clay
• Calcium sulfate (Drierite)

Correct Answer: Molecular sieve (zeolite)

Q14. Which desiccant is commonly used for general moisture control in bottles due to cost-effectiveness?

• Molecular sieve
• Silica gel
• Phosphorus pentoxide
• Sodium hydroxide pellets

Correct Answer: Silica gel

Q15. Adding colloidal silicon dioxide to a hygroscopic powder primarily helps by:

• Increasing compressibility and disintegration time
• Acting as a glidant and adsorbent to reduce caking
• Raising water activity to prevent condensation
• Converting the powder to a hydrate

Correct Answer: Acting as a glidant and adsorbent to reduce caking

Q16. Which statement about lactose forms is most accurate for moisture behavior?

• Anhydrous lactose is more hygroscopic than lactose monohydrate
• Lactose monohydrate is more hygroscopic than anhydrous lactose
• Both forms have identical hygroscopicity
• Neither form absorbs any moisture

Correct Answer: Anhydrous lactose is more hygroscopic than lactose monohydrate

Q17. Microbial growth is generally inhibited in dry powders when water activity (aw) is kept:

• Below 0.3
• Below 0.6
• Below 0.9
• Above 0.95

Correct Answer: Below 0.6

Q18. Which strategy best mitigates sticking and picking when tableting a hygroscopic API?

• Wet granulation with high-moisture binder
• Use dry granulation, low-moisture excipients, and a hydrophobic lubricant coating
• Increase compression speed without changing excipients
• Use sugar coating after compression only

Correct Answer: Use dry granulation, low-moisture excipients, and a hydrophobic lubricant coating

Q19. Deliquescence will occur when ambient RH:

• Is below the material’s critical relative humidity
• Exceeds the material’s deliquescence relative humidity (DRH)
• Is fixed at 25% regardless of material
• Is lower than 10%

Correct Answer: Exceeds the material’s deliquescence relative humidity (DRH)

Q20. Best practice for dispensing a hygroscopic bulk powder to a patient is to:

• Package in paper sachets without any insert
• Use a tight, moisture-resistant container with an appropriate desiccant
• Leave the cap slightly open to vent moisture
• Store in a refrigerator with the cap off

Correct Answer: Use a tight, moisture-resistant container with an appropriate desiccant

Q21. Efflorescent powders are best stored:

• In tightly closed containers to prevent loss of water of crystallization
• In open dishes to allow continuous drying
• With calcium chloride desiccant to drive off water
• At high humidity to encourage caking

Correct Answer: In tightly closed containers to prevent loss of water of crystallization

Q22. Which analytical result measures total mass loss on heating and may include water and other volatiles?

• Karl Fischer water content
• Loss on drying (LOD)
• BET surface area
• X-ray diffraction (XRD) peak area

Correct Answer: Loss on drying (LOD)

Q23. Moisture sorption in many pharmaceutical solids is modeled by which isotherm type?

• Linear Henry’s law isotherm
• Sigmoidal (Type II) GAB model
• Type I Langmuir only
• Type IV capillary with hysteresis only

Correct Answer: Sigmoidal (Type II) GAB model

Q24. Hygroscopic excipients mixed with effervescent systems primarily increase the risk of:

• Inertness of acids and bases
• Premature acid–base reaction and gas evolution
• Reduced dissolution rate in water
• Tablet lamination during coating

Correct Answer: Premature acid–base reaction and gas evolution

Q25. To reduce overall hygroscopicity of a blend, a common formulation change is to:

• Replace mannitol with sorbitol
• Replace sorbitol/lactose with mannitol
• Add sucrose to increase solubility
• Replace fillers with sodium chloride

Correct Answer: Replace sorbitol/lactose with mannitol

Q26. Lowering processing room RH during blending and filling of hygroscopic powders primarily reduces:

• Electrostatic discharge only
• Deliquescence and caking risk
• Tablet friability after compression
• Powder density variability due to vibration

Correct Answer: Deliquescence and caking risk

Q27. At high humidity, hard gelatin capsule shells most likely become:

• Brittle and prone to cracking
• Softer and sticky, risking sealing issues
• Completely impermeable to moisture
• Unaffected within any practical RH range

Correct Answer: Softer and sticky, risking sealing issues

Q28. Which pair correctly matches the excipient with its function for hygroscopic blends?

• Magnesium stearate — hydrophilic binder
• Colloidal silicon dioxide — glidant and moisture adsorbent
• PVP K30 — desiccant
• Microcrystalline cellulose — deliquescent agent

Correct Answer: Colloidal silicon dioxide — glidant and moisture adsorbent

Q29. Hysteresis between adsorption and desorption isotherms in a powder generally indicates:

• No structural changes during sorption
• Capillary condensation and different microstates on wetting/drying
• Purely chemisorptive binding without pores
• Instrumental error only

Correct Answer: Capillary condensation and different microstates on wetting/drying

Q30. Which ICH condition is a standard accelerated test stressing hygroscopicity risk for solid orals?

• 25 °C/40% RH
• 30 °C/65% RH
• 40 °C/75% RH
• 50 °C/20% RH

Correct Answer: 40 °C/75% RH

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