Efflorescent powders MCQs With Answer

Introduction

Efflorescent powders are crystalline hydrates that lose water of crystallization when exposed to air, leading to friability, weight loss, and potential potency variation. Understanding efflorescence is vital in pharmacy compounding, powder technology, and stability studies for B. Pharm students. Key concepts include equilibrium relative humidity (ERH), water activity, vapor pressure driving force, and differences from hygroscopic and deliquescent materials. Common efflorescent substances include sodium carbonate decahydrate, borax, sodium sulfate decahydrate, and copper sulfate pentahydrate. Risk mitigation involves anhydrous substitutions, use of adsorbents, desiccants, moisture-barrier packaging, and controlled humidity storage. Analytical tools like Karl Fischer titration, loss on drying, and TGA help quantify water. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What best defines an efflorescent powder in pharmaceutics?

• A powder that absorbs sufficient moisture to liquefy
• A crystalline hydrate that loses water of crystallization to the atmosphere
• A substance that readily sublimes at room temperature
• A material that undergoes polymorphic conversion upon compression

Correct Answer: A crystalline hydrate that loses water of crystallization to the atmosphere

Q2. The primary thermodynamic driver for efflorescence is when:

• The vapor pressure of water in the hydrate exceeds the ambient water vapor partial pressure
• Ambient temperature is below the glass transition temperature
• The particle size is below 10 micrometers
• There is exposure to light in the near-UV range

Correct Answer: The vapor pressure of water in the hydrate exceeds the ambient water vapor partial pressure

Q3. Which substance is a classic example of an efflorescent material?

• Sucrose
• Calcium chloride dihydrate
• Sodium carbonate decahydrate
• Menthol

Correct Answer: Sodium carbonate decahydrate

Q4. In pharmacy compounding, a key risk with efflorescent powders is:

• Weight loss leading to content variability over time
• Improved flow that enhances dose uniformity
• Increased microbial growth due to higher water activity
• Enhanced lubricity that reduces sticking

Correct Answer: Weight loss leading to content variability over time

Q5. How do efflorescent and deliquescent substances differ?

• Both absorb moisture but only deliquescent substances liquefy
• Efflorescent substances lose water; deliquescent substances absorb moisture and may dissolve
• Efflorescent substances sublime; deliquescent substances polymerize
• There is no practical difference in pharmacy

Correct Answer: Efflorescent substances lose water; deliquescent substances absorb moisture and may dissolve

Q6. The most suitable packaging to minimize efflorescence is:

• Paper sachets with pinholes for ventilation
• Amber glass bottle with a loose cap
• High-barrier container (glass or HDPE) with a tight closure and a desiccant
• Permeable polyethylene bag without insert

Correct Answer: High-barrier container (glass or HDPE) with a tight closure and a desiccant

Q7. A practical compounding strategy for efflorescent powders is to:

• Use glycerin as a humectant to retain water
• Replace the hydrate with the anhydrous equivalent and/or include an adsorbent
• Increase ambient temperature to speed processing
• Granulate with aqueous binder systems

Correct Answer: Replace the hydrate with the anhydrous equivalent and/or include an adsorbent

Q8. Equilibrium relative humidity (ERH) of a hydrate is best described as the:

• Relative humidity at which the hydrate neither gains nor loses water to the air
• Humidity at which dissolution begins
• Humidity at which the substance sublimes
• Temperature at which water activity equals zero

Correct Answer: Relative humidity at which the hydrate neither gains nor loses water to the air

Q9. Which analytical method directly quantifies water content including water of crystallization?

• Karl Fischer titration
• Infrared spectroscopy
• Polarimetry
• Refractive index measurement

Correct Answer: Karl Fischer titration

Q10. To study dehydration steps and kinetics of efflorescence, the most informative technique is:

• Thin-layer chromatography
• Thermogravimetric analysis
• Polarography
• Viscosity measurement

Correct Answer: Thermogravimetric analysis

Q11. In pharmacopeial storage terms, efflorescent powders should generally be stored in a:

• Well-closed container with vents
• Light-resistant container only
• Tight, moisture-resistant container
• Open bin for easy access

Correct Answer: Tight, moisture-resistant container

Q12. Which hydrate is prone to efflorescence under dry air?

• Sodium sulfate decahydrate
• Magnesium stearate
• Lactose monohydrate
• Silica gel

Correct Answer: Sodium sulfate decahydrate

Q13. Which excipient is commonly used to adsorb liberated water in efflorescent powder blends?

• Light magnesium oxide
• Sorbitol
• Sodium lauryl sulfate
• Talc only

Correct Answer: Light magnesium oxide

Q14. What may happen if an efflorescent drug is mixed with a deliquescent excipient?

• No interaction; they are independent
• Mutual absorption leads to improved flow
• Liberated water is absorbed, causing caking or localized liquefaction
• Immediate crystallization of both components

Correct Answer: Liberated water is absorbed, causing caking or localized liquefaction

Q15. During dispensing, to minimize efflorescence the pharmacist should:

• Weigh slowly in a warm environment
• Weigh and transfer rapidly in low-humidity conditions
• Use open boats to encourage airflow
• Pre-wet the powder with ethanol

Correct Answer: Weigh and transfer rapidly in low-humidity conditions

Q16. If a hydrate effloresces before assay and the calculation is on an as-is mass basis, the apparent potency will:

• Decrease
• Increase
• Remain unchanged
• Become unpredictable and immeasurable

Correct Answer: Increase

Q17. Which statement about degree of hydration and efflorescence is most accurate?

• Higher hydrates tend to be more prone to efflorescence at low humidity
• Monohydrates are always more efflorescent
• Hydration state has no effect
• Anhydrous forms effloresce most

Correct Answer: Higher hydrates tend to be more prone to efflorescence at low humidity

Q18. A formulation approach to reduce efflorescence during storage is:

• Microencapsulation with a moisture-barrier polymer
• Exposure to vacuum without protection
• Use of hygroscopic plasticizers
• Addition of high water activity sugars

Correct Answer: Microencapsulation with a moisture-barrier polymer

Q19. To standardize dosing with hydrates, calculations are best performed on which basis?

• Volume basis
• As-is mass basis only
• Anhydrous equivalent basis
• Bulk density basis

Correct Answer: Anhydrous equivalent basis

Q20. Which parameter best predicts the direction of moisture migration in powder blends?

• Bulk density
• Water activity
• Glass transition temperature
• Angle of repose

Correct Answer: Water activity

Q21. Appropriate patient counseling for an efflorescent powder includes:

• Keep the container tightly closed with the desiccant inside; minimize opening time
• Transfer to a paper envelope for breathability
• Store in the bathroom for higher humidity
• Remove the desiccant to avoid contamination

Correct Answer: Keep the container tightly closed with the desiccant inside; minimize opening time

Q22. Which is least likely to be efflorescent?

• Borax (sodium borate decahydrate)
• Calcium chloride dihydrate
• Sodium carbonate decahydrate
• Copper sulfate pentahydrate

Correct Answer: Calcium chloride dihydrate

Q23. A common physical change seen after efflorescence in bulk powders is:

• Reduced dusting
• Increased friability and surface chalking
• Immediate liquefaction
• Formation of a viscous gel

Correct Answer: Increased friability and surface chalking

Q24. Which statement about efflorescence and temperature is correct?

• Higher temperature generally increases the rate of efflorescence by raising water vapor pressure
• Efflorescence only occurs below 0 degrees Celsius
• Temperature has no effect on efflorescence
• Efflorescence ceases at room temperature

Correct Answer: Higher temperature generally increases the rate of efflorescence by raising water vapor pressure

Q25. To create very low relative humidity for efflorescence studies, which desiccant setup is preferred?

• Saturated sodium chloride solution (about 75% RH)
• Phosphorus pentoxide in a desiccator
• Saturated potassium nitrate solution (about 93% RH)
• Saturated magnesium nitrate solution (about 54% RH)

Correct Answer: Phosphorus pentoxide in a desiccator

Q26. In an extemporaneous sachet containing sodium carbonate decahydrate, a prudent approach is to:

• Substitute the anhydrous form with equivalent base and add an inert diluent
• Add water to stabilize the hydrate
• Use paper wraps to allow the powder to breathe
• Increase milling time to generate heat

Correct Answer: Substitute the anhydrous form with equivalent base and add an inert diluent

Q27. During manufacturing, which step most likely induces efflorescence?

• Coating with moisture-barrier polymers
• Vacuum drying at mild heat
• Storage in sealed foil pouches
• Wet granulation with minimal solvent

Correct Answer: Vacuum drying at mild heat

Q28. Which hydrate is both prone to efflorescence and oxidative instability on air exposure?

• Ferrous sulfate heptahydrate
• Magnesium sulfate heptahydrate
• Sodium chloride
• Calcium carbonate

Correct Answer: Ferrous sulfate heptahydrate

Q29. Which packaging choice is least suitable for an efflorescent bulk powder?

• Foil-laminate sachet with heat seal
• Amber glass bottle with tight cap and desiccant
• Paper envelope sealed with tape
• High-density polyethylene bottle with induction seal

Correct Answer: Paper envelope sealed with tape

Q30. Identify the correct classification pairing:

• Efflorescent: sodium sulfate decahydrate; Deliquescent: calcium chloride; Volatile: camphor
• Efflorescent: calcium chloride; Deliquescent: borax; Volatile: lactose
• Efflorescent: sucrose; Deliquescent: talc; Volatile: sodium bicarbonate
• Efflorescent: menthol; Deliquescent: sodium carbonate decahydrate; Volatile: copper sulfate

Correct Answer: Efflorescent: sodium sulfate decahydrate; Deliquescent: calcium chloride; Volatile: camphor

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