Conductometric titrations and their applications MCQs With Answer

Introduction:

Conductometric titrations are an essential analytical technique in pharmaceutical analysis that monitor changes in solution conductivity to determine titration end points. This method uses conductometry and conductivity cells to follow ionic mobility during acid-base, precipitation, complexation, and redox titrations. B. Pharm students will encounter applications in assay validation, impurity profiling, buffer evaluation, and pharmacopoeial methods where conductivity, cell constant, temperature control, and ionic strength influence results. Understanding titration curves, equivalence-point detection, and common interferences (e.g., background electrolytes, weak acids/bases) is crucial for accurate quantitation. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What physical quantity is directly measured in conductometric titrations?

• pH of the solution
• Electrical conductivity of the solution
• Optical absorbance of the solution
• Redox potential of the solution

Correct Answer: Electrical conductivity of the solution

Q2. Which electrode arrangement is typically used in conductometric measurements?

• Reference and indicator electrode
• Two platinum electrodes in a conductivity cell
• A glass electrode and silver/silver chloride electrode
• A mercury drop electrode

Correct Answer: Two platinum electrodes in a conductivity cell

Q3. The unit of specific conductance (conductivity) commonly used in pharmaceutical labs is:

• mol L−1
• Siemens per meter (S m−1)
• Ohm·cm
• pH units

Correct Answer: Siemens per meter (S m−1)

Q4. In a strong acid versus strong base conductometric titration, conductivity behavior before and after the equivalence point is:

• Constant throughout the titration
• Decreases then increases after equivalence point
• Increases then decreases after equivalence point
• Only increases throughout

Correct Answer: Decreases then increases after equivalence point

Q5. What causes the initial decrease in conductivity when titrating HCl with NaOH?

• Formation of nonionic water molecules
• Precipitation of a salt
• Increase in temperature
• Oxidation of chloride

Correct Answer: Formation of nonionic water molecules

Q6. For titration of a weak acid with a strong base, the conductometric curve typically shows:

• A single sharp decrease then increase at equivalence
• A gradual change with a less distinct equivalence point
• No change in conductivity
• Only an increase in conductivity

Correct Answer: A gradual change with a less distinct equivalence point

Q7. In precipitation titrations (e.g., AgNO3 titrating Cl−), conductance usually:

• Remains unchanged because precipitate is ionic
• Decreases as insoluble precipitate removes ions, then increases after excess titrant
• Continuously increases due to added ions
• Oscillates during the titration

Correct Answer: Decreases as insoluble precipitate removes ions, then increases after excess titrant

Q8. The cell constant in conductometry depends on:

• Concentration of titrant only
• Geometry of the conductivity cell (electrode distance and area)
• Type of analyte only
• Temperature only

Correct Answer: Geometry of the conductivity cell (electrode distance and area)

Q9. Which parameter must be controlled or compensated because conductivity is temperature dependent?

• pH
• Cell constant
• Temperature
• Viscosity

Correct Answer: Temperature

Q10. In conductometric titration, background conductivity from supporting electrolyte should be:

• Maximized to increase signal
• Ignored because it has no effect
• Minimized or subtracted to improve endpoint detection
• Only considered for nonaqueous titrations

Correct Answer: Minimized or subtracted to improve endpoint detection

Q11. Which pharmaceutical application commonly uses conductometric titration?

• Assay of nonionic surfactants without ionization
• Determination of chloride content in API or formulations
• Direct measurement of drug melting point
• Quantifying organic impurities by UV

Correct Answer: Determination of chloride content in API or formulations

Q12. Molar conductivity (Λm) is defined as:

• Conductivity multiplied by solution viscosity
• Conductivity divided by molar concentration of electrolyte
• pH times conductance
• Conductivity times cell constant

Correct Answer: Conductivity divided by molar concentration of electrolyte

Q13. Which ionic property most strongly affects conductivity in solution?

• Molar mass of the ion
• Mobility (ionic mobility) of the ion
• Optical activity of the ion
• Color of the ion

Correct Answer: Mobility (ionic mobility) of the ion

Q14. During conductometric titration, a very dilute titrand can lead to:

• Sharper endpoint with large conductance change
• Difficulty detecting endpoint due to low signal-to-noise
• No effect on titration quality
• Automatic precipitation of analyte

Correct Answer: Difficulty detecting endpoint due to low signal-to-noise

Q15. Which interference is most problematic for conductometric chloride determination?

• Nonionic impurities
• Other halides or ions that form similar precipitates (e.g., bromide)
• Solid excipients that do not dissolve
• Volatile organic solvents

Correct Answer: Other halides or ions that form similar precipitates (e.g., bromide)

Q16. Why is a supporting electrolyte sometimes added in conductometric titrations?

• To increase color for endpoint visualization
• To maintain constant ionic strength and reduce migration effects
• To precipitate the analyte before titration
• To change the pH drastically

Correct Answer: To maintain constant ionic strength and reduce migration effects

Q17. Which titration is least suitable for conductometric detection?

• Strong acid vs strong base
• Precipitation titrations giving insoluble salts
• Titration of nonionizing organic compounds without ionic products
• Complexation producing charged complexes

Correct Answer: Titration of nonionizing organic compounds without ionic products

Q18. During titration of acetic acid with NaOH, why is the equivalence point less distinct than for HCl?

• Acetic acid is a weak acid; acetate formation changes ionic mobility gradually
• NaOH does not ionize in water
• Acetic acid precipitates during titration
• Temperature drops dramatically

Correct Answer: Acetic acid is a weak acid; acetate formation changes ionic mobility gradually

Q19. How is the equivalence point determined from a conductometric titration curve?

• By finding the minimum or point of slope change in the conductivity vs volume plot
• By measuring the color change of the solution
• By mass loss during titration
• By extrapolating absorbance at 0 nm

Correct Answer: By finding the minimum or point of slope change in the conductivity vs volume plot

Q20. Which adjustment improves precision in conductometric titrations?

• Using very cold solutions without temperature control
• Calibrating cell constant and controlling temperature
• Adding excess analyte initially
• Agitating intermittently without mixing

Correct Answer: Calibrating cell constant and controlling temperature

Q21. In pharmaceutical QC, conductometric methods are advantageous because they are:

• Non-destructive, simple, fast, and require minimal reagents
• Always more selective than chromatography
• Insensitive to ionic interferences
• Only suitable for volatile compounds

Correct Answer: Non-destructive, simple, fast, and require minimal reagents

Q22. What is the effect of increasing titrant concentration on the titration curve sharpness?

• It generally sharpens the endpoint by larger conductivity change per addition
• It flattens the curve making endpoint invisible
• It changes solution color only
• It removes the need for electrodes

Correct Answer: It generally sharpens the endpoint by larger conductivity change per addition

Q23. Which of the following must be known to convert measured conductance to conductivity?

• Cell constant of the conductivity cell
• Molar mass of analyte
• pKa of analyte
• Volume of titrant only

Correct Answer: Cell constant of the conductivity cell

Q24. Non-aqueous conductometric titrations are used when:

• Analyte is only soluble or stable in nonaqueous solvents
• Water is the best solvent for the analyte
• Temperature control is impossible
• When pH measurements are required

Correct Answer: Analyte is only soluble or stable in nonaqueous solvents

Q25. A conductivity cell shows noisy readings; a likely cause is:

• Stable temperature and well-cleaned electrodes
• Poor electrical contacts, dirty electrodes, or insufficient mixing
• Correct cell constant calibration
• Appropriate ionic strength

Correct Answer: Poor electrical contacts, dirty electrodes, or insufficient mixing

Q26. Which ion typically has higher molar conductivity at infinite dilution?

• Large, heavy anions
• Small ions with high mobility like H+ and OH−
• Neutral organic molecules
• Colloidal particles

Correct Answer: Small ions with high mobility like H+ and OH−

Q27. Conductometric titration can be combined with which other technique to improve selectivity?

• Thermogravimetric analysis
• pH or potentiometric titration monitoring concurrently
• NMR spectroscopy during titration
• DSC analysis

Correct Answer: pH or potentiometric titration monitoring concurrently

Q28. What is the primary limitation of conductometric titrations in complex pharmaceutical matrices?

• They are too selective for multi-ion samples
• Multiple ionic species and excipients can mask the endpoint
• They always require radioactive tracers
• They cannot detect chloride

Correct Answer: Multiple ionic species and excipients can mask the endpoint

Q29. During validation of a conductometric method, which parameter is NOT typically assessed?

• Linearity and range
• Limit of detection and quantitation
• Endpoint color change reproducibility
• Precision and accuracy

Correct Answer: Endpoint color change reproducibility

Q30. Best practice before performing conductometric titration on a drug sample includes:

• Using undiluted sample solids directly in cell
• Proper sample dissolution, filtration of particulates, and temperature equilibration
• Ignoring ionic strength adjustments
• Adding arbitrary surfactants to improve mixing

Correct Answer: Proper sample dissolution, filtration of particulates, and temperature equilibration

G S Sachin

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