Potentiometry is an electroanalytical technique used to determine ion concentrations by measuring the voltage of an electrochemical cell. It plays a crucial role in analytical chemistry, especially in pH determination and titration. Mastering potentiometry is essential for the PPSC Analytical Chemist exam, as it is widely used in laboratory analysis and quality control.

1. What is potentiometry?
   a) Measurement of current under no potential
   b) Measurement of potential under no current flow
   c) Measurement of resistance in a solution
   d) Measurement of pH using a color indicator
   Answer: b
2. The principle of potentiometry involves:
   a) Current flow between electrodes
   b) Potential difference between two electrodes in a solution
   c) Measurement of solution conductivity
   d) Redox reactions only
   Answer: b
3. Which equation is central to potentiometry?
   a) Beer-Lambert Law
   b) Nernst Equation
   c) Henderson-Hasselbalch Equation
   d) Arrhenius Equation
   Answer: b
4. A reference electrode has:
   a) Variable potential
   b) Zero potential
   c) Known, constant potential
   d) No potential
   Answer: c
5. Example of a reference electrode:
   a) Glass electrode
   b) Standard Hydrogen Electrode (SHE)
   c) Fluoride electrode
   d) Antimony electrode
   Answer: b
6. The indicator electrode’s potential is proportional to:
   a) Temperature of the solution
   b) Concentration of the analyte
   c) Volume of the solution
   d) Pressure of the system
   Answer: b
7. Salt bridge functions to:
   a) Increase current flow
   b) Complete the circuit and maintain neutrality
   c) Measure pH
   d) Reduce potential difference
   Answer: b
8. Which salt is NOT used in a salt bridge?
   a) KCl
   b) NaCl
   c) AgNO₃
   d) KNO₃
   Answer: c
9. In the Nernst equation, “n” represents:
   a) Gas constant
   b) Valency of ions
   c) Faraday’s constant
   d) Temperature
   Answer: b
10. The potential of Standard Hydrogen Electrode (SHE) is:
    a) +0.242 V
    b) 0 V
    c) -0.242 V
    d) 1 V
    Answer: b
11. Saturated Calomel Electrode (SCE) has a potential of:
    a) 0 V
    b) +0.242 V
    c) -0.242 V
    d) 1 V
    Answer: b
12. Which electrode is used for pH measurement?
    a) Fluoride electrode
    b) Glass electrode
    c) Antimony electrode
    d) Platinum electrode
    Answer: b
13. The glass electrode is sensitive to:
    a) Na⁺ ions
    b) H⁺ ions
    c) Cl⁻ ions
    d) K⁺ ions
    Answer: b
14. A first-kind electrode consists of:
    a) Metal rod immersed in its ion solution
    b) Inert metal in redox solution
    c) Metal coated with salt precipitate
    d) Glass membrane
    Answer: a
15. Example of a second-kind electrode:
    a) Pt in Fe²⁺/Fe³⁺ solution
    b) Ag/AgCl/KCl
    c) Glass electrode
    d) Sb/SbO electrode
    Answer: b
16. Ion-Selective Electrodes (ISEs) measure:
    a) Only cations
    b) Only anions
    c) Specific ions
    d) All dissolved ions
    Answer: c
17. The lanthanum fluoride electrode is used for:
    a) pH measurement
    b) Fluoride ion measurement
    c) Chloride ion measurement
    d) Sodium ion measurement
    Answer: b
18. Advantage of ISEs:
    a) Slow response time
    b) Affected by sample color
    c) Short response time
    d) Measures only cations
    Answer: c
19. Disadvantage of glass electrodes:
    a) Robust and durable
    b) Easily damaged
    c) Insensitive to H⁺ ions
    d) Requires high current
    Answer: b
20. Potentiometric titrations can be used for:
    a) Acid-base reactions only
    b) Redox, precipitation, and acid-base reactions
    c) Organic synthesis only
    d) Gas chromatography
    Answer: b
21. The antimony-antimony oxide electrode is used for:
    a) pH measurement
    b) Fluoride measurement
    c) Redox reactions
    d) Conductivity measurement
    Answer: a
22. Which electrode is NOT an ISE?
    a) Glass electrode
    b) Fluoride electrode
    c) SHE
    d) Sodium electrode
    Answer: c
23. The junction potential ((E_{junction})) arises due to:
    a) Difference in ion mobility at liquid junctions
    b) Temperature gradients
    c) Electrode material
    d) Salt bridge composition
    Answer: a
24. Primary standard reference electrode:
    a) SCE
    b) Ag/AgCl
    c) SHE
    d) Glass electrode
    Answer: c
25. Secondary standard reference electrode:
    a) SHE
    b) SCE
    c) Pt electrode
    d) Fluoride electrode
    Answer: b
26. The Nernst equation for a single ion is:
    a) (E = E^0 + \frac{RT}{nF} \ln c)
    b) (E = E^0 – \frac{RT}{nF} \ln c)
    c) (E = E^0 + \frac{nF}{RT} \ln c)
    d) (E = E^0 – \frac{nF}{RT} \ln c)
    Answer: a
27. At 25°C, the Nernst slope for a monovalent ion is:
    a) 0.0592 V
    b) 0.0296 V
    c) 0.592 V
    d) 0.0256 V
    Answer: a
28. Which electrode is used in complexometric titrations?
    a) Glass electrode
    b) Ion-selective electrode
    c) Mercury electrode
    d) Platinum electrode
    Answer: b
29. The purpose of a salt bridge is to prevent:
    a) Mixing of analyte solutions
    b) Current flow
    c) Liquid junction potential
    d) Polarization of electrodes
    Answer: a
30. Potentiometry is a type of:
    a) Gravimetric analysis
    b) Electroanalytical chemistry
    c) Spectroscopic analysis
    d) Chromatographic analysis
    Answer: b
31. Which electrode is suitable for non-aqueous titrations?
    a) SHE
    b) Glass electrode
    c) SCE
    d) Antimony electrode
    Answer: b
32. The potential of an indicator electrode depends on:
    a) Temperature only
    b) Concentration of analyte only
    c) Both temperature and analyte concentration
    d) Pressure of the system
    Answer: c
33. Which factor does NOT affect the Nernst equation?
    a) Temperature
    b) Ion valency
    c) Electrode material thickness
    d) Analyte concentration
    Answer: c
34. In the cell notation: Ag|AgCl|KCl || H⁺|H₂|Pt, the double line represents:
    a) Electrode surface
    b) Salt bridge
    c) Reference electrode
    d) Indicator electrode
    Answer: b
35. The glass electrode’s inner solution is typically:
    a) 0.1 M HCl
    b) 1 M NaCl
    c) Saturated KCl
    d) Distilled water
    Answer: a
36. Which ion interferes with the fluoride ISE?
    a) Na⁺
    b) OH⁻
    c) Cl⁻
    d) K⁺
    Answer: b
37. The response time of an ISE is typically:
    a) Seconds to minutes
    b) Hours
    c) Days
    d) Microseconds
    Answer: a
38. Which electrode is used in the determination of pKₐ?
    a) SCE
    b) Glass electrode
    c) Fluoride electrode
    d) Platinum electrode
    Answer: b
39. The antimony electrode is NOT suitable for:
    a) pH 3–8
    b) Strongly acidic solutions
    c) Neutral solutions
    d) Weakly alkaline solutions
    Answer: b
40. Which of the following is a redox electrode?
    a) Ag/AgCl
    b) Pt in Fe²⁺/Fe³⁺ solution
    c) Glass electrode
    d) SCE
    Answer: b
41. The potential of a cell is given by:
    a) (E_{cell} = E_{indicator} – E_{reference})
    b) (E_{cell} = E_{reference} – E_{indicator})
    c) (E_{cell} = E_{reference} + E_{indicator} + E_{junction})
    d) (E_{cell} = E_{indicator} + E_{junction})
    Answer: c
42. Which electrode is used in clinical Na⁺ analysis?
    a) Glass electrode
    b) Sodium ISE
    c) SCE
    d) Antimony electrode
    Answer: b
43. The liquid junction potential is minimized by using:
    a) High concentration of KCl
    b) Distilled water
    c) Non-conductive solutions
    d) Glass membranes
    Answer: a
44. Which of the following is NOT a limitation of ISEs?
    a) Interference from other ions
    b) Fragility
    c) Short response time
    d) Inability to measure turbid samples
    Answer: c
45. The standard potential ((E^0)) is measured under:
    a) 1 M analyte concentration, 1 atm pressure, 25°C
    b) 0.1 M analyte concentration, 1 atm pressure, 25°C
    c) 1 M analyte concentration, 2 atm pressure, 25°C
    d) 0.1 M analyte concentration, 2 atm pressure, 25°C
    Answer: a
46. Which electrode is used in the determination of Cl⁻?
    a) Glass electrode
    b) Ag/AgCl electrode
    c) Fluoride electrode
    d) Sb electrode
    Answer: b
47. The Henderson equation is used to calculate:
    a) (E_{cell})
    b) (pK_a)
    c) Ion concentration
    d) Junction potential
    Answer: b
48. Which of the following is a third-kind electrode?
    a) Ag/AgCl
    b) Pt in Fe²⁺/Fe³⁺
    c) Zn in Zn²⁺
    d) Glass electrode
    Answer: b
49. The electromotive force (EMF) of a cell is zero when:
    a) Concentrations are equal
    b) The cell is at equilibrium
    c) No salt bridge is present
    d) Temperature is 0°C
    Answer: b
50. Which application is NOT for potentiometry?
    a) Soil analysis
    b) Blood electrolyte measurement
    c) UV-Vis spectroscopy
    d) Water quality monitoring
    Answer: c

71. The Nernst equation for a divalent ion at 25°C is:
    a) (E = E^0 + \frac{0.0592}{2} \log c)
    b) (E = E^0 + \frac{0.0296}{2} \log c)
    c) (E = E^0 + 0.0592 \log c)
    d) (E = E^0 – \frac{0.0592}{2} \log c)
    Answer: a
72. The selectivity coefficient ((K_{ij})) for an ISE indicates:
    a) Response to interfering ions
    b) Electrode lifespan
    c) Temperature sensitivity
    d) pH range
    Answer: a
73. The Debye-Hückel equation is used to calculate:
    a) Electrode potential
    b) Activity coefficients
    c) Junction potential
    d) Nernst slope
    Answer: b
74. Which ISE is used for CO₂ measurement?
    a) Glass electrode
    b) Severinghaus electrode
    c) Fluoride electrode
    d) Sodium electrode
    Answer: b
75. The potential of an Ag/AgCl electrode depends on:
    a) [Cl⁻]
    b) [Ag⁺]
    c) Temperature only
    d) Pressure
    Answer: a
76. In a galvanic cell, the anode is:
    a) Where reduction occurs
    b) Where oxidation occurs
    c) Always the reference electrode
    d) Always the indicator electrode
    Answer: b
77. The standard potential of the cell is zero when:
    a) Both electrodes are SHE
    b) No current flows
    c) Concentrations are equal
    d) Temperature is 0°C
    Answer: a
78. Which of the following is NOT a requirement for a salt bridge?
    a) Inertness
    b) High solubility
    c) Precipitate formation
    d) Electrical neutrality maintenance
    Answer: c
79. The pH of a solution is 5. The [H⁺] is:
    a) (10^{-5}) M
    b) (10^{5}) M
    c) 5 M
    d) 0.5 M
    Answer: a
80. The slope of the Nernst equation changes with:
    a) Ion charge
    b) Electrode material
    c) Salt bridge type
    d) Reference electrode
    Answer: a