Deck 12: Electrochemistry: Principles and Measurement

Question 1

Potentiometry:
1)is the measurement of the electrical potential difference between two electrodes
2)is measured in voltage
3)measurements require the use of reference electrodes
4)measurements are mode only when there is no flow of current

A)1, 2, 3, 4
B)1, 2, 3
C)1, 2, 4
D)2, 3, 4

Answer 1

1, 2, 3, 4

Question 2

The use of ion-selective phases in potentiometric measurements is based on the potential that develops:

A)across the ion-selective phase once the ion has been captured in the ion-selective phase
B)after the ion passes through the ion-selective phase into the internal filling solution
C)across the liquid junction located between the tip of the reference electrode and the solution being measured
D)at the Ag/AgCl interface of the reference electrode

Answer 2

across the ion-selective phase once the ion has been captured in the ion-selective phase

Question 3

Carbon dioxide and ammonia electrodes are identical in that they utilize the same ______ and are different in that they utilize different ______.

A)pH electrode for measurement, gas-selective membranes
B)pH electrode for measurement, ionophores
C)gas-selective membranes, reference electrodes for quantification
D)gas-selective membranes, filling solutions around the electrode

Answer 3

pH electrode for measurement, gas-selective membranes

Question 4

Which of the following may result in errant sodium results being reported by the laboratory when using a glass ion-selective electrode?

A)standards used for calibration and sample for analysis are not analyzed at the same temperature
B)electrode fouling by serum, plasma, or whole blood
C)analysis of highly acidic urine samples
D)all of the above

Question 5

One of the characteristics of a reference electrode is that it must produce a constant and reproducible half-cell reaction.For the saturated calomel reference electrode, which component ensures the development of this constant potential?

A)elemental mercury
B)calomel (Hg₂Cl₂)
C)saturated potassium chloride
D)silver chloride

Question 6

In the analysis of carbon dioxide by ion-selective electrode methodology, it is noticed that the instrument response time is longer for carbon dioxide than it is for pH, sodium, or potassium.Which of the following provides the correct explanation for this longer response?

A)The increased response time is needed for the chemical reaction between carbon dioxide and the buffer surrounding the pH electrode.
B)Electrode performance is being lost and requires replacement.
C)The increased response time is needed to allow equilibration of carbon dioxide across the membrane.
D)both a and c

Question 7

Liquid and polymer membranes for ion-selective electrodes utilize a hydrophobic organic ion exchanger or neutral carrier molecule which is known as a/an ______, an example of which is ______ that is selective for potassium ions.

A)potentiostat, tridodecylamine
B)potentiostat, valinomycin
C)ionophore, tridodecylamine
D)ionophore, valinomycin

Question 8

In potentiometric measurements, the voltage difference between the indicator and reference electrodes is proportional to:

A)ion activity
B)ion concentration
C)the logarithm of ion activity
D)the logarithm of ion concentration

Question 9

Which of the following describes the measurement of glucose by selective electrode methodology?

A)The glucose-selective phase will bind the glucose present in the patient sample, allowing the development of a potential across the membrane for measurement.
B)Glucose will selectively diffuse across its selective phase and establish an equilibrium with the internal filling solution prior to direct measurement.
C)Glucose will interact with an immobilized enzyme, producing a product that will be oxidized at the platinum electrode, resulting in measurement.
D)Glucose will selectively pass through a membrane and be titrated, with the time required for titration equated to glucose concentration.

Question 10

The primary application for coulometric analysis of chloride is:

A)the measurement of chloride in urine
B)the measurement of chloride in sweat
C)the measurement of chloride in serum
D)the measurement of chloride in whole blood

Question 11

In the coulometric titration of chloride, the titration end-point is measured in terms of the:

A)time required to complete the titration
B)amount of product (silver chloride) formed
C)amount of silver ion produced at the anode
D)number of electrons detected at the cathode

Question 12

Suppose a new pH electrode was attached to a pH meter.During calibration, the pH meter had a slow response time and continued to drift after adjustments.What should be the technologist's next step?

A)contact the supplier and request a replacement electrode
B)replace the pH meter
C)calibrate with a new set of standards
D)allow the pH electrode to soak for a few hours in buffer

Question 13

The oxygen electrode is designed as a complete electrochemical cell which includes a platinum cathode at which oxygen is ______ by the reaction ______, utilizing electrons produced at the anode.

A)oxidized, O₂ + ₂H+ + ₂e- →H₂O₂
B)reduced, O₂ + ₂H+ + ₂e-→ H₂O₂
C)oxidized, Ago ↔ Ag+ + e-
D)reduced, Ago ↔ Ag+ + e-

Question 14

The typical pH ion-selective phase utilized in a clinical laboratory is subject to which of the following problems?

A)acid error
B)alkaline error
C)interference from calcium and other divalent ions
D)lack of reproducibility

Question 15

What is the most important variable to control during the measurement of ionized calcium by ion-selective electrode methodology?

A)the degree of oxygen exposure
B)the pH of the sample
C)the response time of the instrument
D)all of the above

Question 16

Sodium measurements made by nondilutional ion-selective electrode methods may yield different results from those obtained by dilutional methods.Results determined by _____ methods are altered by specimens that have high lipid or protein levels.An advantage of the ______ method is that this method brings all samples to a constant ionic strength.Changes in the electrode surface are possible with ______ methods.

A)dilutional, dilutional, nondilutional
B)dilutional, nondilutional, dilutional
C)nondilutional, dilutional, nondilutional
D)nondilutional, nondilutional, dilutional

Question 17

Which of the following techniques would be the method of choice for measuring Pb⁺² in urine?

A)potentiometric electrochemical analysis
B)amperometric electrochemical analysis
C)anodic stripping voltammetric electrochemical analysis
D)coulometric electrochemical analysis