Introduction: Kinematic viscosity MCQs With Answer are essential for B. Pharm students studying fluid flow, formulation science, and quality control. Kinematic viscosity—measured in stokes or centistokes—relates a fluid’s internal resistance to flow to its density and is distinct from dynamic viscosity. Understanding measurement techniques (capillary/Ostwald, Ubbelohde, Saybolt), temperature dependence, unit conversions, and practical implications in syrups, suspensions, emulsions, and coatings helps in formulation design and stability assessment. These focused MCQs cover calculations, instruments, standards (USP/ASTM), and typical pharmaceutical scenarios to strengthen conceptual and analytical skills. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the SI unit of kinematic viscosity?
- Pascal-second (Pa·s)
- Newton-second (N·s)
- Square meter per second (m²/s)
- Centipoise (cP)
Correct Answer: Square meter per second (m²/s)
Q2. Kinematic viscosity (ν) is related to dynamic viscosity (μ) and density (ρ) by which formula?
- ν = μ × ρ
- ν = μ / ρ
- ν = ρ / μ
- ν = μ + ρ
Correct Answer: ν = μ / ρ
Q3. Which instrument is commonly used to measure kinematic viscosity in the laboratory?
- Brookfield viscometer
- Ostwald (capillary) viscometer
- Ubbelohde spectrophotometer
- Tensiometer
Correct Answer: Ostwald (capillary) viscometer
Q4. Kinematic viscosity is often reported in centistokes. 1 cSt equals:
- 1 × 10^-6 m²/s
- 1 × 10^-4 m²/s
- 1 × 10^-3 m²/s
- 1 × 10^-2 m²/s
Correct Answer: 1 × 10^-6 m²/s
Q5. Which statement best describes kinematic viscosity?
- It measures the fluid’s mass per unit volume.
- It measures internal resistance to shear independent of density.
- It measures internal resistance to flow normalized by density.
- It measures surface tension effects in liquids.
Correct Answer: It measures internal resistance to flow normalized by density.
Q6. For Newtonian fluids, how does kinematic viscosity vary with shear rate?
- It decreases with increasing shear rate.
- It increases with increasing shear rate.
- It remains constant regardless of shear rate.
- It fluctuates unpredictably.
Correct Answer: It remains constant regardless of shear rate.
Q7. Which of the following viscometers measures kinematic viscosity by timing fluid flow through a capillary under gravity?
- Rotational viscometer
- Falling-ball viscometer
- Capillary (Ostwald/Ubbelohde) viscometer
- Vibrational viscometer
Correct Answer: Capillary (Ostwald/Ubbelohde) viscometer
Q8. Why is temperature control critical when measuring kinematic viscosity?
- Temperature affects only the density, not viscosity.
- Viscosity and density both change with temperature, altering kinematic viscosity significantly.
- Temperature has negligible effect on kinematic viscosity in pharmaceuticals.
- Temperature affects only color and odor, not viscosity.
Correct Answer: Viscosity and density both change with temperature, altering kinematic viscosity significantly.
Q9. Which equation commonly models the temperature dependence of viscosity?
- Arrhenius or Andrade equation
- Newton’s law of cooling
- Van ’t Hoff equation
- Gibbs free energy equation
Correct Answer: Arrhenius or Andrade equation
Q10. In pharmaceutical syrup formulation, why is kinematic viscosity important?
- It determines only the drug’s solubility.
- It affects pourability, mouthfeel, and suspended particle settling rate.
- It controls only the color stability of the syrup.
- It is irrelevant for oral liquid formulations.
Correct Answer: It affects pourability, mouthfeel, and suspended particle settling rate.
Q11. Which unit is used for dynamic viscosity in the CGS system that is often converted in calculations?
- Pascal-second (Pa·s)
- Poise (P)
- Kelvin (K)
- Stokes (St)
Correct Answer: Poise (P)
Q12. Relationship between stokes and centistokes is:
- 1 St = 100 cSt
- 1 St = 10 cSt
- 1 St = 1000 cSt
- 1 St = 0.01 cSt
Correct Answer: 1 St = 100 cSt
Q13. The Reynolds number using kinematic viscosity is defined as:
- Re = ρ v L / μ
- Re = v L / ν
- Re = μ / (ρ v L)
- Re = ν / (v L)
Correct Answer: Re = v L / ν
Q14. Which USP or ASTM practice is relevant for kinematic viscosity measurement?
- USP chapters on dissolution testing
- ASTM D445 for kinematic viscosity of transparent and opaque liquids
- USP monographs on microbial limits
- ASTM methods for particle size only
Correct Answer: ASTM D445 for kinematic viscosity of transparent and opaque liquids
Q15. If a liquid has dynamic viscosity 1.2 mPa·s and density 1.0 g/cm³, its kinematic viscosity in cSt is approximately:
- 0.12 cSt
- 1.2 cSt
- 12 cSt
- 120 cSt
Correct Answer: 1.2 cSt
Q16. Which phenomenon is directly influenced by kinematic viscosity in suspensions?
- Drug degradation kinetics
- Rate of particle sedimentation
- pH stability
- Microbial growth
Correct Answer: Rate of particle sedimentation
Q17. Which viscosity term is independent of density?
- Kinematic viscosity
- Dynamic viscosity
- Specific viscosity
- Relative density
Correct Answer: Dynamic viscosity
Q18. Which viscometer type is preferred for non-Newtonian formulations like gels?
- Capillary viscometer
- Rotational (Brookfield) viscometer
- U-tube manometer
- Mercury viscometer
Correct Answer: Rotational (Brookfield) viscometer
Q19. The Andrade equation relates viscosity to temperature using which functional form?
- Linear increase with temperature
- Arrhenius-type exponential relationship
- Logarithmic decrease independent of activation energy
- Quadratic dependency
Correct Answer: Arrhenius-type exponential relationship
Q20. Which sample preparation step is critical before measuring kinematic viscosity?
- Diluting to extreme concentrations always
- Removing air bubbles and equilibrating to measurement temperature
- Adding preservative agents
- Heating to boiling point
Correct Answer: Removing air bubbles and equilibrating to measurement temperature
Q21. In capillary viscometry, the flow time is proportional to:
- Density only
- Dynamic viscosity divided by density (kinematic viscosity)
- Surface tension only
- Concentration of solute only
Correct Answer: Dynamic viscosity divided by density (kinematic viscosity)
Q22. Which factor does NOT typically affect kinematic viscosity of a pharmaceutical liquid?
- Temperature
- Concentration of solutes
- Applied magnetic field (normal conditions)
- Presence of suspended particles
Correct Answer: Applied magnetic field (normal conditions)
Q23. Saybolt viscometer reports which viscosity units often used in industry?
- Seconds (Saybolt Universal Seconds)
- Centistokes
- Pascal-seconds
- Stokes
Correct Answer: Seconds (Saybolt Universal Seconds)
Q24. Which conversion is correct: 1 mPa·s equals how many cP?
- 1 mPa·s = 10 cP
- 1 mPa·s = 1 cP
- 1 mPa·s = 0.1 cP
- 1 mPa·s = 100 cP
Correct Answer: 1 mPa·s = 1 cP
Q25. Kinematic viscosity of water at 20°C is approximately:
- 1 cSt
- 10 cSt
- 0.1 cSt
- 100 cSt
Correct Answer: 1 cSt
Q26. Which of the following describes viscosity index (VI)?
- A measure of fluid’s color stability
- A measure of how viscosity changes with temperature
- A measure of density variation with pressure
- A measure of pH sensitivity
Correct Answer: A measure of how viscosity changes with temperature
Q27. In fluid dynamics, lower kinematic viscosity typically promotes:
- Lamination and lower tendency to turbulence at given velocity and dimension
- Turbulence more easily at given velocity and dimension
- Higher drag always
- Instant solidification
Correct Answer: Turbulence more easily at given velocity and dimension
Q28. For an emulsion, an increase in kinematic viscosity generally will:
- Increase creaming and phase separation rate
- Reduce droplet coalescence by improving physical stability
- Increase drug degradation rate exclusively
- Convert the emulsion to a gas
Correct Answer: Reduce droplet coalescence by improving physical stability
Q29. Which liquid would likely have the highest kinematic viscosity at room temperature?
- Water
- Glycerin
- Ethanol
- Hexane
Correct Answer: Glycerin
Q30. When converting dynamic viscosity (mPa·s) to kinematic viscosity (cSt) for aqueous solutions, you typically divide by:
- Density in g/cm³
- Viscosity index
- Temperature in °C
- Concentration percentage
Correct Answer: Density in g/cm³
Q31. Which error source is common in capillary viscometry?
- Neglecting gravitational acceleration changes
- Timing errors and incorrect temperature control
- Magnetic interference
- Viscosity index miscalculation only
Correct Answer: Timing errors and incorrect temperature control
Q32. In quality control, reporting kinematic viscosity at a specified temperature (e.g., 40°C) ensures:
- Comparability between batches and instruments
- That density is constant across samples
- pH remains unchanged
- Microbial growth is prevented
Correct Answer: Comparability between batches and instruments
Q33. The presence of high molecular weight polymers in a solution typically causes:
- Decrease in kinematic viscosity
- Increase in kinematic viscosity and potential non-Newtonian behavior
- No change in viscosity
- Evaporation of the solvent
Correct Answer: Increase in kinematic viscosity and potential non-Newtonian behavior
Q34. Which is true about kinematic viscosity measurement for opaque or particulate-laden liquids?
- Capillary viscometers cannot be used; use methods like rotational viscometry or calibrated relative methods.
- Capillary viscometers always work irrespective of opacity.
- Opacity affects only density measurements.
- Opaque liquids have zero kinematic viscosity.
Correct Answer: Capillary viscometers cannot be used; use methods like rotational viscometry or calibrated relative methods.
Q35. The term “centistokes” is most closely associated with which physical quantity?
- Dynamic viscosity
- Kinematic viscosity
- Density
- Surface tension
Correct Answer: Kinematic viscosity
Q36. When validating a viscometer, one should:
- Ignore calibration fluids and proceed directly to samples
- Use certified viscosity standards at the same temperature range as samples
- Use any liquid and assume instrument is accurate
- Calibrate only once when purchased
Correct Answer: Use certified viscosity standards at the same temperature range as samples
Q37. In laminar flow through a pipe, an increase in kinematic viscosity will generally:
- Decrease the pressure drop for a given flow rate
- Increase the pressure drop for a given flow rate
- Not affect flow resistance
- Instantly cause turbulent flow
Correct Answer: Increase the pressure drop for a given flow rate
Q38. Which pharmaceutical process requires precise knowledge of kinematic viscosity for spray formation?
- Tablet compression
- Aerosol and spray nozzle atomization
- Lyophilization
- Sterility testing
Correct Answer: Aerosol and spray nozzle atomization
Q39. How does dissolved solids concentration typically affect kinematic viscosity of aqueous solutions?
- Increased concentration usually increases kinematic viscosity
- Increased concentration always decreases kinematic viscosity
- Concentration has no effect
- It only affects color, not viscosity
Correct Answer: Increased concentration usually increases kinematic viscosity
Q40. Which term describes a fluid whose viscosity decreases with increasing shear rate?
- Newtonian
- Dilatant (shear-thickening)
- Pseudoplastic (shear-thinning)
- Bingham plastic exclusively
Correct Answer: Pseudoplastic (shear-thinning)
Q41. Kinematic viscosity plays a role in which aspect of topical ointment performance?
- Drug chemical structure only
- Spreadability and residence time on skin
- Color fastness only
- Sterility of ointment
Correct Answer: Spreadability and residence time on skin
Q42. Which of the following is a direct method to measure kinematic viscosity?
- Measuring torque on a spindle
- Timing flow through a calibrated capillary at constant temperature
- Measuring electrical conductivity
- Determining refractive index
Correct Answer: Timing flow through a calibrated capillary at constant temperature
Q43. When reporting kinematic viscosity in a lab notebook, you should always include:
- Only the value and nothing else
- Value, temperature, instrument type, and calibration status
- Only the instrument brand
- The room color and humidity only
Correct Answer: Value, temperature, instrument type, and calibration status
Q44. In a falling-sphere viscometer, what additional property is needed along with fall time to calculate kinematic viscosity?
- Sphere’s color
- Sphere size and density, and liquid density
- pH of the liquid only
- Magnetic susceptibility
Correct Answer: Sphere size and density, and liquid density
Q45. Which practice helps reduce systematic error in viscosity measurement?
- Varying temperature during measurement
- Using unclean viscometer tubes
- Ensuring temperature equilibration and using clean, calibrated equipment
- Measuring without calibration standards
Correct Answer: Ensuring temperature equilibration and using clean, calibrated equipment
Q46. For high-viscosity ointment bases, which method is most useful to assess flow behavior?
- Capillary viscometer at low shear
- Rotational rheometer or rotational viscometer at controlled shear
- Conductivity meter
- UV spectrophotometry
Correct Answer: Rotational rheometer or rotational viscometer at controlled shear
Q47. A formulation scientist wants to reduce sedimentation in a suspension; they should:
- Reduce the kinematic viscosity of the medium
- Increase kinematic viscosity moderately to slow particle settling
- Remove all viscosity modifiers
- Increase temperature to boiling
Correct Answer: Increase kinematic viscosity moderately to slow particle settling
Q48. Which relationship helps convert dynamic viscosity (μ in Pa·s) to kinematic viscosity (ν in m²/s)?
- ν = μ × ρ
- ν = μ / ρ
- ν = μ + ρ
- ν = ρ / μ
Correct Answer: ν = μ / ρ
Q49. During formulation scale-up, why monitor kinematic viscosity?
- To ensure sensory properties and processability remain consistent at larger scale
- It is unnecessary during scale-up
- Only color changes matter during scale-up
- To increase microbial contamination intentionally
Correct Answer: To ensure sensory properties and processability remain consistent at larger scale
Q50. Which statement is true about kinematic viscosity and drug delivery performance?
- Kinematic viscosity has no impact on drug release from topical or liquid dosage forms.
- Appropriate kinematic viscosity influences release rate, spreadability, and stability of dosage forms.
- Only chemical additives control drug release; viscosity is irrelevant.
- Higher kinematic viscosity always improves drug bioavailability.
Correct Answer: Appropriate kinematic viscosity influences release rate, spreadability, and stability of dosage forms.
