Capillary viscometer MCQs With Answer

Capillary viscometer MCQs With Answer

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Capillary viscometer MCQs With Answer is a focused review designed for B. Pharm students preparing for exams and practicals in pharmaceutics and physical pharmacy. This concise guide covers capillary viscometer principles, types (Ostwald, Ubbelohde, Cannon-Fenske), Poiseuille’s law, kinematic and dynamic viscosity, calibration constants, temperature control, and data analysis including relative, specific and intrinsic viscosity. Emphasis is placed on experimental technique, error sources, Reynolds number criteria, and viscosity–temperature relationships relevant to drug formulations, polymer solutions and rheological evaluation. Practice through targeted questions boosts conceptual understanding and lab competence. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What fundamental law describes flow through a capillary viscometer under laminar conditions?

  • Bernoulli’s principle
  • Poiseuille’s law
  • Newton’s cooling law
  • Hooke’s law

Correct Answer: Poiseuille’s law

Q2. Which viscometer is specifically designed to eliminate hydrostatic head effects by having a suspended capillary bulb?

  • Ostwald viscometer
  • Ubbelohde viscometer
  • Cannon-Fenske viscometer
  • Falling-sphere viscometer

Correct Answer: Ubbelohde viscometer

Q3. Kinematic viscosity is defined as:

  • Dynamic viscosity divided by density
  • Density divided by dynamic viscosity
  • Shear stress divided by shear rate
  • Flow time multiplied by capillary constant

Correct Answer: Dynamic viscosity divided by density

Q4. Which unit is commonly used for kinematic viscosity in pharmacy labs?

  • Pascal-second (Pa·s)
  • Centipoise (cP)
  • Centistokes (cSt)
  • Newton (N)

Correct Answer: Centistokes (cSt)

Q5. The viscometer constant (K) in Ostwald viscometry relates viscosity to which measurable quantity?

  • Flow time squared
  • Flow time
  • Pressure drop
  • Capillary radius only

Correct Answer: Flow time

Q6. Relative viscosity (ηr) is defined as:

  • Viscosity of solvent divided by viscosity of solution
  • Viscosity of solution divided by viscosity of solvent
  • Difference between solution and solvent viscosity
  • Ratio of dynamic to kinematic viscosity

Correct Answer: Viscosity of solution divided by viscosity of solvent

Q7. Specific viscosity (ηsp) equals:

  • ηr − 1
  • ln(ηr)
  • ηr × density
  • ηr + 1

Correct Answer: ηr − 1

Q8. Intrinsic viscosity [η] is obtained experimentally by extrapolating which function to zero concentration?

  • Specific viscosity vs. concentration
  • Reduced viscosity vs. concentration
  • Flow time vs. capillary constant
  • Relative viscosity vs. temperature

Correct Answer: Reduced viscosity vs. concentration

Q9. Which equation relates reduced viscosity to intrinsic viscosity and a concentration-dependent term (Huggins constant)?

  • Arrhenius equation
  • Huggins equation
  • Kraemer equation
  • Einstein relation

Correct Answer: Huggins equation

Q10. For accurate capillary viscometry, flow must be laminar. Which criterion quantifies laminar flow?

  • High Reynolds number (>4000)
  • Low Reynolds number (<2000)
  • Shear rate must be zero
  • Reynolds number between 2000–4000

Correct Answer: Low Reynolds number (<2000)

Q11. Which temperature effect is most critical when measuring viscosity of pharmaceutical solutions?

  • Viscosity typically increases with temperature
  • Viscosity typically decreases with temperature
  • Viscosity is independent of temperature
  • Viscosity oscillates with temperature

Correct Answer: Viscosity typically decreases with temperature

Q12. The activation energy for viscous flow can be estimated using which relationship?

  • Van’t Hoff equation
  • Arrhenius-type equation
  • Henderson-Hasselbalch equation
  • Poiseuille’s linear form

Correct Answer: Arrhenius-type equation

Q13. When using an Ostwald viscometer, which reading method is standard for flow time?

  • Measure mass loss over time
  • Use upper and lower meniscus passage between marks
  • Observe color change at capillary exit
  • Measure pressure at the reservoir

Correct Answer: Use upper and lower meniscus passage between marks

Q14. Which property must be known to convert kinematic viscosity to dynamic viscosity?

  • Surface tension
  • Density of the fluid
  • Viscometer constant only
  • Capillary length

Correct Answer: Density of the fluid

Q15. In capillary viscometry, what is the effect of air bubbles in the sample?

  • Decrease measured flow time slightly
  • No effect on measurement
  • Cause large errors by interrupting flow and altering time
  • Stabilize flow and improve accuracy

Correct Answer: Cause large errors by interrupting flow and altering time

Q16. Which of the following is a primary source of systematic error in viscometry?

  • Operator eye color
  • Inaccurate timing and temperature control
  • Using distilled water as solvent
  • Excess sample volume

Correct Answer: Inaccurate timing and temperature control

Q17. The Cannon-Fenske viscometer is particularly suitable for measuring:

  • Very low-viscosity gases
  • Non-Newtonian suspensions only
  • Liquids of known density to determine kinematic viscosity
  • High-pressure polymer melts

Correct Answer: Liquids of known density to determine kinematic viscosity

Q18. The Huggins constant gives information about:

  • Solvent vapor pressure
  • Polymer–polymer and polymer–solvent interactions
  • Electrical conductivity of solution
  • Capillary diameter changes

Correct Answer: Polymer–polymer and polymer–solvent interactions

Q19. Which correction must be applied when using a viscometer at different temperatures than calibration?

  • Capillary color correction
  • Temperature correction for viscometer constant or viscosity values
  • No correction necessary
  • pH correction

Correct Answer: Temperature correction for viscometer constant or viscosity values

Q20. Specific viscosity is useful for dilute polymer solutions because it is proportional to:

  • Polymer concentration at low concentrations
  • Shear stress squared
  • Capillary length
  • Solvent molar mass

Correct Answer: Polymer concentration at low concentrations

Q21. Which method is used to obtain intrinsic viscosity from Huggins and Kraemer plots?

  • Average the intercepts of ln(ηr) vs concentration
  • Extrapolate reduced and inherent viscosity plots to zero concentration and average
  • Use only the highest concentration reading
  • Measure viscosity at boiling point

Correct Answer: Extrapolate reduced and inherent viscosity plots to zero concentration and average

Q22. In Ostwald viscometry, the viscometer constant K depends on:

  • Fluid color and refractive index
  • Capillary dimensions and geometry
  • Ambient air pressure only
  • Solution ionic strength

Correct Answer: Capillary dimensions and geometry

Q23. Which viscosity measurement is independent of fluid density?

  • Dynamic viscosity
  • Kinematic viscosity
  • Relative viscosity
  • Density viscosity

Correct Answer: Dynamic viscosity

Q24. For polymer molecular weight estimation using intrinsic viscosity, which Mark–Houwink relationship form is used?

  • [η] = K·M^a (Mark–Houwink equation)
  • [η] = ln(M)/K
  • [η] = M/K^a
  • [η] = K + a·M

Correct Answer: [η] = K·M^a (Mark–Houwink equation)

Q25. Reynolds number in a capillary depends on which parameters?

  • Velocity, characteristic dimension, and fluid viscosity/density
  • Only fluid color and temperature
  • Capillary manufacturer and age
  • Operator’s timing skill

Correct Answer: Velocity, characteristic dimension, and fluid viscosity/density

Q26. What is reduced viscosity (ηred)?

  • Specific viscosity divided by concentration
  • Relative viscosity times concentration
  • Logarithm of flow time
  • Density divided by viscosity

Correct Answer: Specific viscosity divided by concentration

Q27. Which solvent property can significantly change measured viscosity and must be controlled?

  • pH only
  • Temperature and solvent composition
  • Capillary wall color
  • Ambient light intensity

Correct Answer: Temperature and solvent composition

Q28. Why is cleaning of glass capillary viscometers critical between measurements?

  • Residual film changes capillary diameter and wetting, causing errors
  • Cleaning makes them look nicer only
  • To alter the viscometer constant intentionally
  • Cleaning is unnecessary for aqueous samples

Correct Answer: Residual film changes capillary diameter and wetting, causing errors

Q29. Which sample behavior invalidates simple capillary viscometry assumptions?

  • Newtonian fluid behavior
  • Non-Newtonian (shear-thinning or thixotropic) behavior
  • Constant density with temperature
  • Transparent solutions

Correct Answer: Non-Newtonian (shear-thinning or thixotropic) behavior

Q30. The Kraemer equation relates ln(ηr)/c to concentration and is used together with Huggins to determine:

  • Solvent vapor pressure
  • Intrinsic viscosity and Huggins constant
  • Capillary length
  • Absolute molecular weight directly

Correct Answer: Intrinsic viscosity and Huggins constant

Q31. If the measured flow time of solvent is 100 s and solution is 150 s, what is the relative viscosity?

  • 0.67
  • 1.5
  • 250
  • 50

Correct Answer: 1.5

Q32. Which practice improves precision when timing viscometer flow?

  • Use multiple replicate timings and average them
  • Time only once per sample
  • Change meniscus marks between runs
  • Allow large temperature swings during runs

Correct Answer: Use multiple replicate timings and average them

Q33. What is the effect of increasing capillary radius on flow time for a given fluid under laminar flow?

  • Flow time increases
  • Flow time decreases
  • Flow time remains the same
  • Flow stops completely

Correct Answer: Flow time decreases

Q34. Which of the following is a reason to use Ubbelohde over Ostwald viscometer?

  • Ubbelohde is cheaper
  • Ubbelohde eliminates hydrostatic head and allows accurate timing independent of filling level
  • Ostwald cannot measure any liquids
  • Ubbelohde measures dynamic viscosity directly without density

Correct Answer: Ubbelohde eliminates hydrostatic head and allows accurate timing independent of filling level

Q35. For very low-viscosity fluids, which precaution helps reduce timing error?

  • Increase capillary temperature dramatically
  • Use viscometers with smaller capillaries or shorter flow paths
  • Use colored dyes only
  • Measure only one replicate

Correct Answer: Use viscometers with smaller capillaries or shorter flow paths

Q36. Which parameter is directly proportional to the flow rate in Poiseuille’s law for a cylindrical capillary?

  • Capillary length
  • Pressure difference across the capillary
  • Fluid viscosity
  • Fluid density squared

Correct Answer: Pressure difference across the capillary

Q37. A typical lab reports dynamic viscosity in mPa·s. What is 1 mPa·s equivalent to?

  • 1 Pa·s
  • 0.001 Pa·s
  • 1000 Pa·s
  • 1 cSt

Correct Answer: 0.001 Pa·s

Q38. When determining intrinsic viscosity for polymer solutions, why keep concentrations low?

  • To avoid polymer–polymer interactions that deviate from ideal dilute behavior
  • Low concentrations speed up flow time exclusively
  • High concentrations are more accurate
  • Low concentration prevents temperature changes

Correct Answer: To avoid polymer–polymer interactions that deviate from ideal dilute behavior

Q39. Which experimental factor affects both kinematic viscosity measurement and density measurement when converting to dynamic viscosity?

  • Ambient light level
  • Accuracy of temperature control
  • Capillary brand label
  • Operator’s clothing

Correct Answer: Accuracy of temperature control

Q40. In viscometric data analysis, plotting ln(ηr) vs. concentration gives a line used in which equation?

  • Kraemer equation
  • Huggins equation
  • Arrhenius equation
  • Poiseuille’s law

Correct Answer: Kraemer equation

Q41. Which of the following samples is most likely to show non-Newtonian behavior affecting capillary viscometry?

  • Dilute aqueous glucose solution
  • Suspension of polymeric microspheres or concentrated gel
  • Pure ethanol
  • Distilled water

Correct Answer: Suspension of polymeric microspheres or concentrated gel

Q42. What is the main advantage of capillary viscometers in pharmaceutical labs?

  • They measure viscosity of solids
  • They provide accurate, reproducible kinematic viscosity for low to moderate viscosities with small sample volumes
  • They are unaffected by temperature
  • They directly measure molecular weight

Correct Answer: They provide accurate, reproducible kinematic viscosity for low to moderate viscosities with small sample volumes

Q43. When calculating intrinsic viscosity, which constant describes solvent quality and polymer interactions in Mark–Houwink?

  • K (Mark–Houwink constant)
  • Avogadro’s number
  • Planck’s constant
  • Reynolds constant

Correct Answer: K (Mark–Houwink constant)

Q44. If a viscometer is calibrated with water at 20 °C, what must be done to measure viscosity at 25 °C?

  • Use the same calibration constant without change
  • Apply temperature correction or recalibrate at 25 °C
  • Ignore temperature because water is inert
  • Change capillary to a different brand

Correct Answer: Apply temperature correction or recalibrate at 25 °C

Q45. Which of the following best describes dynamic viscosity (η)?

  • Resistance to flow under gravity per unit density
  • Shear stress divided by shear rate (fluid’s internal resistance to flow)
  • Only relevant for gases
  • Always equal to kinematic viscosity

Correct Answer: Shear stress divided by shear rate (fluid’s internal resistance to flow)

Q46. In practical lab technique, why is it important to pre-equilibrate the viscometer and sample at the measurement temperature?

  • To allow meniscus to change color
  • To ensure stable temperature and avoid viscosity drift during timing
  • Pre-equilibration is unnecessary
  • To change the viscometer constant automatically

Correct Answer: To ensure stable temperature and avoid viscosity drift during timing

Q47. Which correction accounts for the kinetic energy of flowing liquid for very short flow times (e.g., less than ~100 s)?

  • Stefan correction
  • Kinetic energy or inertia correction (Weissenberg–Rabinowitsch type adjustments)
  • pH correction
  • Colorimetric correction

Correct Answer: Kinetic energy or inertia correction (Weissenberg–Rabinowitsch type adjustments)

Q48. For a dilute polymer solution, intrinsic viscosity is most informative about:

  • Ionization constant of solvent
  • Polymer molecular size and conformation in that solvent
  • Color of polymer
  • pH of solution only

Correct Answer: Polymer molecular size and conformation in that solvent

Q49. Which practice reduces surface tension effects when filling a capillary viscometer?

  • Use a very high filling head each time
  • Rinse and wet the capillary thoroughly and avoid trapped bubbles
  • Introduce air bubbles intentionally
  • Use inconsistent filling volumes

Correct Answer: Rinse and wet the capillary thoroughly and avoid trapped bubbles

Q50. When reporting viscometric data for publication, which details are essential?

  • Only the final viscosity value
  • Temperature, viscometer type, calibration constant, solvent density, concentration and method of averaging
  • Only the brand of viscometer
  • Ambient music played during the experiment

Correct Answer: Temperature, viscometer type, calibration constant, solvent density, concentration and method of averaging

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