Question 1

Which of the following is a key advantage of electroanalytical methods compared to spectroscopic and chromatographic techniques?

Accepted Answer

They provide information about activities rather than just concentrations.

Question 2

Michael Faraday’s law of electrolysis states that the amount of substance deposited at an electrode is proportional to which of the following?

Accepted Answer

The chemical equivalent weight of the substance.

Question 3

Which equation, developed by Walter Nernst, relates the cell potential to ion activity?

Accepted Answer

$$E = E^0$ - \frac{0.0592}{n} \log Q$$

Question 4

Which of the following is NOT a main branch of electroanalytical chemistry?

Accepted Answer

Spectrophotometry

Question 5

In a potentiometric cell, what is the primary function of the reference electrode?

Accepted Answer

To provide a constant, known potential independent of the analyte solution.

Question 6

Which of the following is a disadvantage of the calomel reference electrode?

Accepted Answer

Its potential changes slowly with temperature due to solubility equilibrium.

Question 7

A silver/silver chloride electrode is preferred over a calomel electrode in which scenario?

Accepted Answer

When measurements are performed at temperatures above 60°C.

Question 8

Which type of metallic indicator electrode is used to determine the activity of the cation derived from the electrode metal itself?

Accepted Answer

Electrode of the first kind

Question 9

What is the main difference between a metallic indicator electrode and a membrane indicator electrode?

Accepted Answer

Metallic electrodes develop potential from redox reactions at the surface, while membrane electrodes develop a junction potential across a selective membrane.

Question 10

A glass pH electrode must be soaked in water before use. What is the primary reason for this?

Accepted Answer

To hydrate the glass membrane, enabling ion exchange.

Question 11

A pH electrode shows a slope of 0.05916 V per pH unit at 25°C. What does this indicate about the electrode?

Accepted Answer

It is functioning ideally according to the Nernst equation.

Question 12

Which error occurs in glass pH electrodes at very high pH values due to interference from sodium ions?

Accepted Answer

Alkaline error

Question 13

Given the cell potential equation for a combination pH electrode: $$E_{cell} = L - 0.0592 	imes 	ext{pH}$$, if $$E_{cell} = -0.352 V $$and $$L = 0.122 V$$, what is the pH?

Accepted Answer

$$7.84$$

Question 14

Which of the following best describes the operational definition of pH using potentiometry?

Accepted Answer

pH is defined as $$-\frac{E_{cell} - k}{0.0592}$$ where $$E_{cell} is $$the measured cell potential and $$k is a $$constant determined by calibration.

Question 15

A sodium-selective electrode has a selectivity coefficient $$K_{Na,K} = 0.24$$ for potassium. If the solution contains $$1.50 	imes 10$$^{-3}$$ M Na+ and 1.20$$ 	imes $$10^{-3} M K$$+, what is the effective activity sensed by the electrode?

Accepted Answer

$$1.50 	imes 10$$^{-3}$$ + 0.24 	imes 1.20 	imes 10$$^{-3}$$

Question 16

During a potentiometric titration of Fe$$^{2+}$$ with Ce$$^{4+}$$, what is the cell potential at the equivalence point if $$E^0$$_{$$Fe^{3+}/Fe$$^{2+}$$} = 0.771 V $$and $$E^0$$_{$$Ce^{4+}/Ce$$^{3+}$$} = 1.61 V$$?

Accepted Answer

$$1.19 V$$

Question 17

Which of the following is a correct expression for the cell potential in direct potentiometry for a cation $$X^{n+}$$?

Accepted Answer

$$E_{cell} = K - \frac{0.0592}{n} pX$$

Question 18

A potentiometric titration curve is plotted as electrode potential versus titrant volume. What does the first derivative of this curve ($$\Delta E/\Delta V) $$indicate?

Accepted Answer

The rate of change of potential with respect to titrant volume, highlighting the equivalence point.

Question 19

Which property is NOT required for an ion-selective membrane?

Accepted Answer

High solubility in analyte solutions

Electrochemical Techniques and Potentiometry in Analytical Chemistry

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