Evaporation is a core unit operation in pharmaceutical manufacturing, covering concentration, solvent removal, drying, crystallization and formulation processing. B.Pharm students should learn practical applications of evaporation, including rotary evaporators for lab-scale solvent recovery, falling- and rising-film and multiple-effect evaporators for large-scale concentration, vacuum evaporation for heat-sensitive APIs, and vapor recompression for energy efficiency. Key concepts include mass and heat transfer, steam economy, fouling, residual solvent control and scale-up challenges to preserve product quality and comply with regulatory requirements. Understanding these topics helps optimize yield, reduce degradation and select appropriate equipment and parameters for drug development and production. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary pharmaceutical application of evaporation?
- Particle size reduction
- Solvent removal and concentration of drug solutions
- Sterile filtration
- Granulation
Correct Answer: Solvent removal and concentration of drug solutions
Q2. Which evaporator is commonly used in labs for gentle solvent removal from small volumes?
- Multiple-effect evaporator
- Rotary evaporator
- Falling film evaporator
- Forced circulation evaporator
Correct Answer: Rotary evaporator
Q3. Why is vacuum evaporation preferred for heat-sensitive APIs?
- It increases boiling point of solvents
- It allows evaporation at lower temperatures
- It eliminates the need for condensers
- It enhances solvent polarity
Correct Answer: It allows evaporation at lower temperatures
Q4. Which parameter directly lowers the boiling point of a liquid during evaporation?
- Increase in pressure
- Decrease in pressure (vacuum)
- Increase in solute concentration
- Adding nonvolatile solute
Correct Answer: Decrease in pressure (vacuum)
Q5. What does steam economy in a multiple-effect evaporator indicate?
- Amount of steam used per kg of vapor produced
- Number of effects in series
- Energy recovered from condensate
- Amount of heat lost to environment
Correct Answer: Amount of steam used per kg of vapor produced
Q6. In pharmaceutical evaporation, fouling primarily affects which aspect?
- Color of the product
- Heat transfer efficiency
- pH of the solution
- Viscosity of the vapor
Correct Answer: Heat transfer efficiency
Q7. Which evaporator type is most suitable for highly viscous pharmaceutical feeds?
- Falling film evaporator
- Rising film evaporator
- Forced circulation evaporator
- Rotary evaporator
Correct Answer: Forced circulation evaporator
Q8. Vapor recompression in evaporation is used to:
- Increase solvent volatility
- Improve energy efficiency by recycling vapor heat
- Sterilize the feed
- Reduce feed viscosity
Correct Answer: Improve energy efficiency by recycling vapor heat
Q9. Which quality concern is critical when evaporating solvents from APIs?
- Particle color only
- Residual solvent levels and degradation products
- Electrical conductivity of vapor
- Amount of dissolved gases
Correct Answer: Residual solvent levels and degradation products
Q10. Multiple-effect evaporators are advantageous because they:
- Use more steam than single-effect units
- Improve steam economy by using vapor from one effect to heat the next
- Require no condensers
- Operate only at atmospheric pressure
Correct Answer: Improve steam economy by using vapor from one effect to heat the next
Q11. Which factor does NOT significantly influence evaporation rate?
- Surface area for evaporation
- Temperature difference (driving force)
- Molecular weight of nonvolatile solute
- Air or vapor velocity above the surface
Correct Answer: Molecular weight of nonvolatile solute
Q12. Boiling point elevation due to a nonvolatile solute affects evaporation by:
- Lowering the boiling point
- Raising the boiling point and reducing vapor pressure
- Changing solvent polarity
- Increasing vapor density but not temperature
Correct Answer: Raising the boiling point and reducing vapor pressure
Q13. In pharmaceutical practice, evaporation is often used prior to which downstream process?
- Tablet coating
- Crystallization and drying
- Capsule filling only
- Lyophilization exclusively
Correct Answer: Crystallization and drying
Q14. Which evaporator design minimizes residence time to reduce thermal degradation?
- Batch pan evaporator
- Falling film evaporator
- Agitated thin film evaporator
- Tray dryer
Correct Answer: Agitated thin film evaporator
Q15. For concentrating a heat-sensitive aqueous drug solution, best choice is:
- Open kettle evaporation at high temperature
- Vacuum evaporation with low temperature
- Direct steam injection
- Freeze-thaw concentration
Correct Answer: Vacuum evaporation with low temperature
Q16. Which is a regulatory guideline relevant to solvent removal by evaporation?
- ICH Q3C residual solvents guideline
- ICH Q6A dissolution testing only
- USP heavy metals chapter only
- WHO cold chain guideline
Correct Answer: ICH Q3C residual solvents guideline
Q17. Evaporative crystallization is useful because:
- It always yields amorphous solids
- It concentrates solute to supersaturation to induce crystal formation
- It removes impurities by filtration rather than solubility changes
- It reduces the need for solvents
Correct Answer: It concentrates solute to supersaturation to induce crystal formation
Q18. Which parameter is critical to control to avoid bumping during evaporation?
- pH of solution
- Agitation and boiling surface disturbance
- Color of the container
- Ambient humidity
Correct Answer: Agitation and boiling surface disturbance
Q19. In a falling film evaporator, the liquid travels:
- Horizontally along tubes
- As a thin film down the inner surface of tubes
- Upward inside tubes due to vapor lift
- As droplets in a spray chamber only
Correct Answer: As a thin film down the inner surface of tubes
Q20. Which advantage does a thin film evaporator offer for pharmaceutical concentrates?
- High residence time and low shear
- Low heat transfer coefficient
- Short residence time and efficient heat transfer for viscous or heat-sensitive feeds
- Elimination of condensers
Correct Answer: Short residence time and efficient heat transfer for viscous or heat-sensitive feeds
Q21. During solvent evaporation, loss of volatile impurities is minimized by:
- Operating at very high temperatures
- Using vacuum evaporation and controlled temperature
- Eliminating condensers
- Adding volatile co-solvents
Correct Answer: Using vacuum evaporation and controlled temperature
Q22. Which evaporator is most energy efficient for large-scale sugar or syrup concentration used in pharma excipients?
- Single-effect evaporator
- Multiple-effect evaporator
- Open pan
- Rotary evaporator
Correct Answer: Multiple-effect evaporator
Q23. What does ‘steam stripping’ during evaporation help remove?
- Nonvolatile solutes
- Volatile impurities and residual solvents
- Microbial contaminants only
- Solid particles
Correct Answer: Volatile impurities and residual solvents
Q24. Which calculation concept is essential for designing evaporator heat transfer area?
- Mass spectrometry
- Heat transfer coefficient and log mean temperature difference
- Refractive index of solution
- pKa of drug
Correct Answer: Heat transfer coefficient and log mean temperature difference
Q25. What is a common indicator of scale formation in evaporators?
- Increased heat transfer coefficient
- Reduced heat transfer and increased surface temperature
- Lower feed viscosity
- Improved vacuum level
Correct Answer: Reduced heat transfer and increased surface temperature
Q26. Which method is typically used to recover solvent after evaporation in a pharma plant?
- Direct vent to atmosphere
- Condensation and solvent recovery system
- Discarding vapor as waste
- Absorption into solid adsorbents only
Correct Answer: Condensation and solvent recovery system
Q27. In rotary evaporators, what is the role of reduced pressure?
- Increase solvent boiling point
- Allow solvent to boil at lower temperatures for gentle evaporation
- Disable condensation
- Prevent rotation of the flask
Correct Answer: Allow solvent to boil at lower temperatures for gentle evaporation
Q28. Evaporation followed by crystallization affects polymorphism because:
- Supersaturation and kinetics influence crystal form
- Evaporation always yields the same polymorph
- Polymorphism is independent of solvent removal method
- Only cooling affects polymorphs
Correct Answer: Supersaturation and kinetics influence crystal form
Q29. Which solvent property most strongly influences evaporation rate under identical conditions?
- Surface tension only
- Vapor pressure
- Color
- Optical rotation
Correct Answer: Vapor pressure
Q30. What is a major safety concern in solvent evaporation operations?
- Formation of nonflammable vapors
- Fire and explosion due to flammable solvent vapors
- Excessive cooling of equipment
- Over-sterilization of product
Correct Answer: Fire and explosion due to flammable solvent vapors
Q31. Spray drying differs from evaporation in that spray drying:
- Is a phase change from liquid to solid by rapid solvent evaporation of droplets
- Concentrates solutions by boiling under vacuum
- Is identical to falling film evaporation
- Always yields crystalline solids
Correct Answer: Is a phase change from liquid to solid by rapid solvent evaporation of droplets
Q32. When concentrating sterile parenteral solutions, which evaporative approach is preferred?
- Open pan evaporation with no control
- Closed system under controlled aseptic conditions and validated sterilization
- Outdoor evaporation to speed up process
- Use of non-validated home equipment
Correct Answer: Closed system under controlled aseptic conditions and validated sterilization
Q33. Which control variable is most important to maintain product quality during evaporation?
- Ambient light intensity
- Temperature and pressure (vacuum) control
- Color of feed tank
- Type of flooring in plant
Correct Answer: Temperature and pressure (vacuum) control
Q34. Azeotropic behavior during evaporation can cause:
- Simple removal of one component only
- Co-evaporation of solvent and solute or constant boiling mixtures complicating separation
- No change in composition of vapor
- Always easier solvent recovery
Correct Answer: Co-evaporation of solvent and solute or constant boiling mixtures complicating separation
Q35. Which analysis is commonly used to confirm residual solvent levels after evaporation?
- High performance liquid chromatography (HPLC) only
- Gas chromatography (GC) with suitable detectors
- Microscopy
- Karl Fischer titration only
Correct Answer: Gas chromatography (GC) with suitable detectors
Q36. In scale-up of evaporation processes, what is a typical challenge?
- Maintaining identical color
- Matching heat transfer coefficients and residence times to avoid degradation or incomplete concentration
- Reducing facility size
- Eliminating need for condensers
Correct Answer: Matching heat transfer coefficients and residence times to avoid degradation or incomplete concentration
Q37. Which evaporator is often used for concentrating heat-stable, low-viscosity feeds?
- Falling film evaporator
- Agitated thin film evaporator
- Freeze dryer
- Rotary spray dryer
Correct Answer: Falling film evaporator
Q38. What role does the condenser play in an evaporator system?
- Generates steam for heating
- Condenses vapor to recover solvent and control vacuum
- Removes solids only
- Increases vapor pressure
Correct Answer: Condenses vapor to recover solvent and control vacuum
Q39. Which practice reduces fouling in evaporators processing pharmaceutical feeds?
- Operating at excessively high surface temperatures
- Periodic cleaning and controlling feed concentration and temperature
- Ignoring pH control
- Running without condensers
Correct Answer: Periodic cleaning and controlling feed concentration and temperature
Q40. For solvent recovery of flammable organic solvents, which safety measure is essential?
- Use of open flames nearby to speed evaporation
- Inerting with nitrogen and explosion-proof equipment
- Removal of all condensers
- High-speed fans to vent vapors outdoors
Correct Answer: Inerting with nitrogen and explosion-proof equipment
Q41. What is the significance of residence time in evaporative crystallization?
- It determines color only
- It influences nucleation and crystal growth, affecting crystal size and form
- It is irrelevant to crystal properties
- It only affects pH
Correct Answer: It influences nucleation and crystal growth, affecting crystal size and form
Q42. Which is a typical reason to choose a rising film evaporator over falling film?
- For very viscous fluids
- When vapor flow assists liquid motion at higher heat fluxes for low-viscosity feeds
- To maximize fouling
- For high solid content feeds only
Correct Answer: When vapor flow assists liquid motion at higher heat fluxes for low-viscosity feeds
Q43. How does dissolved nonvolatile solute concentration change vapor pressure of the solvent?
- It increases vapor pressure
- It reduces vapor pressure according to Raoult’s law for ideal solutions
- It does not change vapor pressure
- It doubles vapor pressure always
Correct Answer: It reduces vapor pressure according to Raoult’s law for ideal solutions
Q44. Which maintenance activity extends life and performance of evaporators?
- Neglecting seals
- Regular inspection, cleaning, and replacement of heat transfer surfaces and seals
- Running at maximum temperature always
- Bypassing condensers regularly
Correct Answer: Regular inspection, cleaning, and replacement of heat transfer surfaces and seals
Q45. In pharmaceutical concentration of a syrup, what is an unwanted effect of overheating?
- Sterilization
- Caramelization, API degradation, and color changes
- Lower viscosity
- Improved solubility of API always
Correct Answer: Caramelization, API degradation, and color changes
Q46. Which parameter helps estimate energy requirement for evaporation per kg of solvent removed?
- Latent heat of vaporization of the solvent
- Melting point of solute
- Viscosity of solid impurities
- Dielectric constant
Correct Answer: Latent heat of vaporization of the solvent
Q47. What is the main advantage of using a condenser with solvent recovery during evaporation?
- Increases environmental release of solvents
- Allows recycling of solvent and reduces emissions and costs
- Makes system more flammable
- Reduces product quality only
Correct Answer: Allows recycling of solvent and reduces emissions and costs
Q48. Which evaporation technique is most appropriate for removing trace organic solvents from finished dosage forms?
- High temperature open evaporation
- Vacuum drying or controlled vacuum evaporation at low temperature
- Use of acids to neutralize solvents
- Direct sunlight exposure
Correct Answer: Vacuum drying or controlled vacuum evaporation at low temperature
Q49. Which monitoring parameter indicates efficient evaporation in an industrial evaporator?
- Stable vacuum and expected distillate flow rate
- Increasing feed volume without change in distillate
- Constant high temperature of heating medium with no vapor
- Rising pressure in condenser only
Correct Answer: Stable vacuum and expected distillate flow rate
Q50. When selecting an evaporator for scale-up, which multidisciplinary knowledge is most useful?
- Only organic chemistry
- Heat and mass transfer, process engineering, solvent chemistry and regulatory considerations
- Only packaging design
- Only marketing strategies
Correct Answer: Heat and mass transfer, process engineering, solvent chemistry and regulatory considerations
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.
Mail- Sachin@pharmacyfreak.com