Potentiometry is a versatile electrochemical technique that measures the potential difference in a solution. For B.Pharm students, mastering potentiometry is key to performing accurate titrations without visual indicators, making it ideal for colored or turbid pharmaceutical solutions. This quiz covers the principles of electrochemical cells, the function of reference and indicator electrodes, and the methods for determining titration end points, all essential concepts in modern pharmaceutical analysis.
- Potentiometry is an analytical method that measures the:
- Conductance of a solution
- Current flowing through a cell
- Potential difference of an electrochemical cell
- Resistance of a solution
- An electrochemical cell used in potentiometry consists of an indicator electrode and a(n):
- Working electrode
- Reference electrode
- Auxiliary electrode
- Dropping mercury electrode
- The defining characteristic of a reference electrode is that it maintains a:
- Constant and known potential
- Variable potential
- High electrical current
- High resistance
- Which of the following is considered the primary reference electrode?
- Calomel electrode
- Silver/Silver chloride electrode
- Standard Hydrogen Electrode (SHE)
- Glass electrode
- An indicator electrode is one whose potential depends on the:
- Temperature of the solution
- Overall current in the cell
- Activity of a specific ion in the solution
- Potential of the reference electrode
- The glass electrode is selectively sensitive to which ion?
- Sodium ions (Na⁺)
- Chloride ions (Cl⁻)
- Hydrogen ions (H⁺)
- Calcium ions (Ca²⁺)
- In a potentiometric titration, the end point is identified by the:
- Point of maximum color change
- Point of maximum conductance
- Point of maximum (steepest) change in potential
- Point of minimum potential
- The saturated calomel electrode (SCE) uses which materials in its construction?
- Silver, silver chloride, and KCl
- Mercury, mercurous chloride, and KCl
- Platinum and hydrogen gas
- A thin glass membrane
- The potential of the Standard Hydrogen Electrode (SHE) is arbitrarily defined as:
- 1.00 V
- 0.50 V
- 0.00 V
- -0.50 V
- A platinum electrode is a common type of ______ indicator electrode.
- ion-selective
- membrane
- redox
- metallic
- The Nernst equation relates the electrode potential to the:
- Temperature and pressure
- Concentration of the ions in the solution
- Volume of the solution
- Conductance of the cell
- A silver/silver chloride electrode is an example of a(n):
- Indicator electrode
- Reference electrode
- Gas-sensing electrode
- Metal electrode
- What is a major advantage of potentiometric titrations?
- They are faster than manual titrations.
- They can be used for colored or turbid solutions.
- They do not require a titrant.
- They measure temperature changes.
- The end point of a potentiometric titration can be accurately determined by plotting the:
- First or second derivative of the titration curve
- Potential versus temperature
- Conductance versus volume
- Absorbance versus concentration
- A metal electrode, such as a silver wire, can be used as an indicator electrode for:
- pH measurements
- Redox reactions
- The concentration of its own ions (e.g., Ag⁺)
- Anion concentration
- The thin, sensitive part of a glass electrode is made of a special:
- Glass membrane
- Platinum wire
- Ceramic frit
- Salt bridge
- Which of the following is a disadvantage of the Standard Hydrogen Electrode?
- It has an unstable potential.
- It is difficult to set up and maintain.
- It cannot be used in acidic solutions.
- It is not very accurate.
- The instrument used to measure the potential difference in potentiometry is a:
- Conductometer
- Ammeter
- Potentiometer (or high-impedance voltmeter/pH meter)
- Polarimeter
- A potentiometric titration curve plots E (potential) against:
- Time
- Temperature
- Volume of titrant
- pH
- The salt bridge in an electrochemical cell serves to:
- Allow the flow of electrons between half-cells
- Allow the flow of ions to maintain electrical neutrality
- Separate the indicator and reference electrodes
- Measure the temperature of the solution
- Which type of titration can be monitored using potentiometry?
- Acid-base
- Redox
- Precipitation
- All of the above
- The potential of an indicator electrode should be:
- Constant
- Proportional to the logarithm of the analyte’s activity
- Zero at all times
- Equal to the reference electrode potential
- The calomel electrode is named after the common name for:
- Mercury (I) chloride
- Mercury (II) chloride
- Potassium chloride
- Silver chloride
- In the titration of a strong acid with a strong base, the largest change in potential occurs:
- At the beginning of the titration
- In the buffer region
- At the equivalence point
- After the equivalence point
- The glass electrode is the most widely used example of a(n):
- Redox electrode
- Metal electrode
- Ion-selective electrode
- Reference electrode
- Which of the following is NOT a characteristic of an ideal reference electrode?
- It has a constant and reproducible potential.
- It is easy to assemble and maintain.
- Its potential changes with the concentration of the analyte.
- It is insensitive to the composition of the analyte solution.
- A plot of ΔE/ΔV versus volume of titrant will show a:
- Sigmoidal curve
- V-shaped curve
- Sharp peak at the end point
- Straight line
- An important component of most reference electrodes is a solution of:
- Saturated potassium chloride (KCl)
- Dilute hydrochloric acid (HCl)
- Pure water
- Saturated sodium sulphate (Na₂SO₄)
- When a potentiometric titration is performed, why is it important to stir the solution?
- To keep the electrodes clean
- To ensure the solution is homogeneous after each addition of titrant
- To increase the conductivity
- To prevent polarization
- A combination electrode is an assembly where:
- Two indicator electrodes are combined.
- The indicator and reference electrodes are combined into a single unit.
- Two reference electrodes are combined.
- The electrode is used for both conductometry and potentiometry.
- The potential of a silver/silver chloride electrode depends on the concentration of which ion?
- Ag⁺
- H⁺
- Cl⁻
- K⁺
- Potentiometry is a “zero current” technique, meaning:
- The potential is always zero.
- The measurement is taken while drawing as little current as possible.
- No electrons are transferred.
- The cell has no resistance.
- The second derivative plot (Δ²E/ΔV²) of a titration curve is useful because:
- It gives a sharper peak than the first derivative plot.
- The end point is where the curve crosses the zero axis.
- It is a sigmoidal curve.
- It directly measures pH.
- The internal reference electrode in a standard glass pH electrode is typically:
- A calomel electrode
- A standard hydrogen electrode
- A silver/silver chloride electrode
- A platinum electrode
- Which of the following can be used to perform a redox titration potentiometrically?
- A glass electrode and a calomel electrode
- A platinum electrode and a calomel electrode
- Two glass electrodes
- Two calomel electrodes
- The term “asymmetry potential” in a glass electrode refers to a small potential that exists even when the pH is the same inside and outside the membrane. This is considered a source of:
- Error
- Precision
- Current
- Stability
- For direct potentiometric measurements (e.g., pH measurement), the system must be:
- Titrated
- Calibrated with standard solutions
- Heated
- Cooled
- The potential of a glass electrode is dependent on the:
- Thickness of the glass membrane
- Difference in H⁺ ion concentration across the membrane
- Concentration of the internal filling solution
- Size of the electrode
- Which component of an electrochemical cell is NOT required for direct potentiometry?
- A reference electrode
- An indicator electrode
- A potential measuring device
- A burette
- A major advantage of the Ag/AgCl electrode over the calomel electrode is that it:
- Is less expensive.
- Can be used at higher temperatures.
- Does not contain mercury.
- Is more accurate.
- The ‘alkaline error’ or ‘sodium error’ affects which electrode at high pH?
- Calomel electrode
- Platinum electrode
- Glass electrode
- Silver/silver chloride electrode
- In a precipitation titration monitored by potentiometry (e.g., Cl⁻ with Ag⁺), the indicator electrode would be:
- A glass electrode
- A platinum electrode
- A silver electrode
- A hydrogen electrode
- A potentiometric measurement is considered to be:
- Destructive to the sample
- Non-destructive to the sample
- A type of chromatography
- A type of spectroscopy
- The main function of a pH meter is to measure the potential difference and convert it directly into a:
- Current reading
- pH value
- Conductance value
- Resistance value
- Which electrode’s potential is described by the equation E = E° – (RT/nF)ln[Products]/[Reactants]?
- All electrodes
- The indicator electrode
- The reference electrode
- The entire cell
- What is a “junction potential”?
- The potential of the reference electrode.
- A potential that develops at the interface between two dissimilar electrolyte solutions (e.g., at the tip of a salt bridge).
- The potential of the indicator electrode.
- The potential at the end point of a titration.
- To get an accurate end point, the volume increments of the titrant added should be ______ near the equivalence point.
- larger
- smaller
- constant
- added rapidly
- An electrode of the first kind is a simple metal electrode in equilibrium with:
- A different metal ion
- Its own ions in solution
- An inert gas
- A non-metal
- The response time of a glass electrode is typically:
- Very slow (minutes)
- Very fast (a few seconds)
- Instantaneous
- Dependent on the color of the solution
- The primary application of potentiometry in pharmaceutical analysis is for:
- Determining melting points
- Identifying functional groups
- End-point detection in titrations
- Measuring particle size
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.
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