MCQ Quiz: Conductometry

Conductometry is an important electrochemical method of analysis that measures the electrical conductivity of a solution. For B.Pharm students, understanding conductometry is essential for applications like determining the endpoint of titrations, especially for colored or turbid solutions, and for assessing the purity of pharmaceutical-grade water. This quiz explores the principles of conductance, the components of a conductivity cell, and the interpretation of conductometric titration curves.

1. Conductometry is an analytical method based on the measurement of a solution’s:
   • Potential
   • Current
   • Resistance
   • Conductance
   Answer: Conductance
2. The ability of a solution to conduct an electric current is due to the presence of:
   • Electrons
   • Ions
   • Neutrons
   • Uncharged molecules
   Answer: Ions
3. The unit of electrical conductance is:
   • Ohm
   • Volt
   • Siemens
   • Ampere
   Answer: Siemens
4. A standard conductivity cell consists of two parallel electrodes made of:
   • Silver
   • Copper
   • Platinized platinum
   • Glass
   Answer: Platinized platinum
5. In a conductometric titration, the end point is determined by a sharp change in:
   • Color
   • Temperature
   • Conductance
   • pH
   Answer: Conductance
6. The cell constant of a conductivity cell is defined as:
   • The distance between the electrodes divided by their surface area
   • The surface area of the electrodes divided by the distance between them
   • The product of the distance and surface area of the electrodes
   • The conductance of a standard solution
   Answer: The distance between the electrodes divided by their surface area
7. The conductance of a solution generally ______ with an increase in temperature.
   • increases
   • decreases
   • remains constant
   • becomes zero
   Answer: increases
8. Which of the following ions has the highest ionic mobility in aqueous solution?
   • Na⁺
   • K⁺
   • H⁺
   • Cl⁻
   Answer: H⁺
9. In the titration of a strong acid (HCl) with a strong base (NaOH), what happens to the conductance before the equivalence point?
   • It increases rapidly.
   • It decreases.
   • It remains constant.
   • It increases slowly.
   Answer: It decreases.
10. The main advantage of conductometric titration is its suitability for:
    • Highly concentrated solutions only
    • Colored or turbid solutions
    • Non-aqueous solutions only
    • Gaseous samples
    Answer: Colored or turbid solutions
11. Specific conductance (conductivity) is the conductance of:
    • One equivalent of an electrolyte
    • One mole of an electrolyte
    • A 1 cm cube of the solution
    • The entire volume of the solution in the cell
    Answer: A 1 cm cube of the solution
12. The platinization of platinum electrodes in a conductivity cell is done to:
    • Increase the surface area and reduce polarization effects
    • Make the electrodes inert
    • Decrease the cell constant
    • Increase the distance between the electrodes
    Answer: Increase the surface area and reduce polarization effects
13. In the titration of a weak acid (CH₃COOH) with a strong base (NaOH), the initial conductance is low because:
    • The weak acid is only slightly ionized
    • The strong base is fully ionized
    • Water has a high conductance
    • The salt formed is insoluble
    Answer: The weak acid is only slightly ionized
14. After the equivalence point in the titration of HCl with NaOH, the conductance increases sharply due to the excess of:
    • H⁺ ions
    • OH⁻ ions
    • Na⁺ ions
    • Cl⁻ ions
    Answer: OH⁻ ions
15. Which instrument is used to measure the conductance of a solution?
    • Potentiometer
    • Polarimeter
    • Conductometer
    • Spectrophotometer
    Answer: Conductometer
16. Equivalent conductance is the specific conductance multiplied by the:
    • Volume of the solution containing one gram equivalent of the solute
    • Concentration in normality
    • Cell constant
    • Resistance of the solution
    Answer: Volume of the solution containing one gram equivalent of the solute
17. The shape of the conductometric titration curve for a strong acid versus a weak base is:
    • V-shaped
    • L-shaped
    • A straight horizontal line followed by an increasing line
    • A continuously increasing curve
    Answer: A straight horizontal line followed by an increasing line
18. Which of the following does NOT affect the conductance of a solution?
    • Nature of the ions
    • Concentration of the ions
    • Temperature of the solution
    • Color of the solution
    Answer: Color of the solution
19. Ohm’s law states that the current (I) is directly proportional to the:
    • Resistance (R)
    • Voltage (E)
    • Conductance (G)
    • Cell constant (K)
    Answer: Voltage (E)
20. Conductance is the reciprocal of:
    • Resistance
    • Voltage
    • Current
    • Specific conductance
    Answer: Resistance
21. In the titration of a weak acid with a strong base, the conductance ______ after the equivalence point.
    • decreases
    • remains constant
    • increases sharply
    • becomes zero
    Answer: increases sharply
22. The cell constant is determined by measuring the conductance of a standard solution of:
    • NaCl
    • KCl
    • HCl
    • NaOH
    Answer: KCl
23. Why is an AC current used in conductometric measurements instead of a DC current?
    • To prevent electrolysis and polarization of the electrodes
    • AC current is more stable
    • DC current cannot pass through the solution
    • AC current is easier to measure
    Answer: To prevent electrolysis and polarization of the electrodes
24. In a precipitation titration, such as AgNO₃ vs KCl, the conductance near the equivalence point:
    • Changes very sharply
    • Remains almost constant
    • Shows a rounded curve, making the end point less sharp
    • Decreases to zero
    Answer: Shows a rounded curve, making the end point less sharp
25. The mobility of an ion in solution is dependent on its:
    • Size and charge
    • Color
    • Molecular weight
    • Atomic number
    Answer: Size and charge
26. In the conductometric titration of a mixture of a strong acid and a weak acid with a strong base, how many end points are observed?
    • Zero
    • One
    • Two
    • Three
    Answer: Two
27. A major application of direct conductometry is:
    • Determining the pKa of a weak acid
    • Checking the purity of distilled or deionized water
    • Identifying an unknown substance
    • Measuring the concentration of a colored solution
    Answer: Checking the purity of distilled or deionized water
28. The unit of specific conductance (conductivity) is:
    • Siemens (S)
    • S cm⁻¹
    • S cm² eq⁻¹
    • Ohm cm
    Answer: S cm⁻¹
29. Which ion has the highest ionic mobility after H⁺?
    • Na⁺
    • K⁺
    • OH⁻
    • Cl⁻
    Answer: OH⁻
30. The titration curve in conductometry is a plot of conductance against:
    • pH
    • Time
    • Temperature
    • Volume of titrant added
    Answer: Volume of titrant added
31. The decrease in conductance when NaOH is added to HCl is due to the replacement of high-mobility H⁺ ions with:
    • Lower-mobility OH⁻ ions
    • Lower-mobility Na⁺ ions
    • Lower-mobility Cl⁻ ions
    • Water molecules
    Answer: Lower-mobility Na⁺ ions
32. Conductometric titrations are less accurate for:
    • Dilute solutions
    • Highly concentrated solutions where ionic interactions are significant
    • Weak acid titrations
    • Strong acid titrations
    Answer: Highly concentrated solutions where ionic interactions are significant
33. The equivalence point in a conductometric titration is found by:
    • Observing a color change
    • Reading a potential value
    • The intersection of two extrapolated straight lines
    • Measuring the temperature change
    Answer: The intersection of two extrapolated straight lines
34. Which principle is the basis of conductometry?
    • The absorption of light by the solution
    • The rotation of plane-polarized light
    • The movement of ions in an electric field
    • The potential difference between two electrodes
    Answer: The movement of ions in an electric field
35. The unit of cell constant is:
    • cm
    • cm⁻¹
    • cm²
    • S cm
    Answer: cm⁻¹
36. In the titration of silver nitrate with potassium chloride, the conductance of the solution before the equivalence point:
    • Increases
    • Decreases
    • Remains nearly constant
    • Decreases sharply
    Answer: Remains nearly constant
37. Which factor is carefully controlled in conductometric measurements because it has a significant effect on conductivity?
    • Pressure
    • Light
    • Temperature
    • Humidity
    Answer: Temperature
38. The term “equivalent conductance” increases with dilution because:
    • The speed of ions increases.
    • The degree of ionization increases for weak electrolytes.
    • The cell constant changes.
    • The viscosity of the solution decreases.
    Answer: The degree of ionization increases for weak electrolytes.
39. Which titration would result in a V-shaped curve?
    • Weak acid vs Strong base
    • Strong acid vs Weak base
    • Strong acid vs Strong base
    • Precipitation titration
    Answer: Strong acid vs Strong base
40. Conductometric titration is not suitable for reactions that produce:
    • A large change in conductance
    • A small change in conductance
    • A high concentration of electrolytes that mask the change
    • A precipitate
    Answer: A high concentration of electrolytes that mask the change
41. The apparatus used for conductometric measurements is a part of a(n):
    • Potentiometer circuit
    • Wheatstone bridge circuit
    • Ammeter circuit
    • Voltmeter circuit
    Answer: Wheatstone bridge circuit
42. In the titration of a weak acid (CH₃COOH) with a weak base (NH₄OH), the titration curve:
    • Is sharp and well-defined
    • Is not sharp and difficult to interpret
    • Is a perfect V-shape
    • Shows no change in conductance
    Answer: Is not sharp and difficult to interpret
43. Specific resistance (resistivity) is the reciprocal of:
    • Conductance
    • Resistance
    • Specific conductance (conductivity)
    • Molar conductance
    Answer: Specific conductance (conductivity)
44. The minimum conductance in a strong acid-strong base titration occurs:
    • At the start of the titration
    • At the equivalence point
    • After the equivalence point
    • At the half-equivalence point
    Answer: At the equivalence point
45. What is a major disadvantage of conductometry?
    • It is not very sensitive.
    • It cannot be used for dilute solutions.
    • It is a non-specific method.
    • It requires a visual indicator.
    Answer: It is a non-specific method.
46. In conductometric titrations, measurements are taken:
    • Only at the end point
    • Only at the start and end
    • Before and after the end point
    • Continuously throughout the titration
    Answer: Before and after the end point
47. The mobility of an ion is inversely proportional to the:
    • Temperature of the solution
    • Charge on the ion
    • Viscosity of the medium
    • Applied voltage
    Answer: Viscosity of the medium
48. In the titration of HCl with NH₄OH, the conductance after the equivalence point:
    • Increases sharply
    • Decreases
    • Remains almost constant
    • Increases slowly
    Answer: Remains almost constant
49. The purpose of using large, platinized electrodes is to:
    • Minimize the resistance of the cell
    • Maximize polarization effects
    • Ensure the cell constant remains at 1.0
    • Measure the pH of the solution
    Answer: Minimize the resistance of the cell
50. One of the key applications of conductometry in the pharmaceutical industry is the:
    • Determination of drug-protein binding
    • Assay of multi-vitamin tablets
    • Determination of the limit test for heavy metals
    • Measurement of total solids in “Water for Injection”
    Answer: Measurement of total solids in “Water for Injection”

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