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Chapter 21: Problem 25

What is the difference between an active and an inactive electrode? Why are inactive electrodes used? Name two substances commonly used for inactive electrodes.

Short Answer

Expert verified
Active electrodes participate in reactions; inactive electrodes do not. Inactive electrodes provide stability. Platinum and graphite are common inactive electrodes.

Step by step solution

01

- Understand the concept of electrodes

Electrodes are conductors through which electricity enters or leaves a medium, such as an electrolyte in a battery or electrochemical cell.
02

- Define active and inactive electrodes

Active electrodes participate in the chemical reactions occurring in the electrolyte, whereas inactive electrodes do not participate in the chemical reactions but merely conduct electrons.
03

- Reasons for using inactive electrodes

Inactive electrodes are used to provide a stable and inert conductive surface that does not interfere with the chemical reactions of the electrochemical process. They ensure accurate and consistent readings or outputs.
04

- Examples of substances used as inactive electrodes

Two substances commonly used for inactive electrodes are platinum and graphite, because they are chemically inert and good conductors of electricity.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Active Electrodes
Active electrodes play a crucial role in electrochemistry. These electrodes participate in the chemical reactions occurring in the electrolyte within an electrochemical cell.
For example, in a copper-zinc galvanic cell, the copper and zinc electrodes are considered active electrodes.
They are involved in oxidation and reduction reactions, which are essential to the operation of the cell. Active electrodes help in accomplishing the electrochemical processes.
Their materials can change in mass or composition during the operation because they are directly involved in the chemical reactions.
Inactive Electrodes
Inactive electrodes, unlike active electrodes, do not partake in the chemical reactions within the electrolyte.
Their main role is to provide a stable conducting medium for the transfer of electrons.
Inactive electrodes are also known as inert electrodes.
They remain unaltered during electrochemical reactions, making them ideal for processes where only the movement of electrons is required but not the electrodes' involvement in the reaction.
This characteristic ensures accurate and consistent readings or outputs without interference.
Common substances used for inactive electrodes include platinum and graphite.
Electrochemical Cell
An electrochemical cell is a device used to generate electrical energy from chemical reactions or to facilitate chemical reactions through the introduction of electrical energy.
There are two main types of electrochemical cells:
  • Galvanic (or Voltaic) Cells: These cells generate electrical energy spontaneously from chemical reactions.
  • Electrolytic Cells: These cells use electrical energy to drive non-spontaneous chemical reactions.
Both types of cells contain electrodes, where oxidation and reduction reactions occur. The movement of electrons between the electrodes is due to the redox reactions taking place within the cell.
Platinum Electrodes
Platinum electrodes are widely used as inactive electrodes due to their exceptional chemical stability and conductivity.
Platinum does not easily react with substances, making it an ideal inert electrode.
It can be found in various electrochemical cells, including those used in laboratories and industrial applications.
Though platinum is an excellent inert material, its high cost is a consideration.
Its unique properties, however, make it indispensable for precision electrochemical measurements and experiments.
Graphite Electrodes
Graphite electrodes, like platinum electrodes, are often used as inactive electrodes.
Graphite is a form of carbon that is conductive and chemically inert.
It is a cost-effective alternative to platinum while still providing excellent performance.
Graphite electrodes are commonly used in applications such as electrolysis and electroplating.
Their availability and affordability make them popular choices for both educational and industrial purposes.
The stable nature of graphite ensures reliable electron transfer without participating in the chemical reactions.

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Most popular questions from this chapter

Balance the following skeleton reactions, and identify the oxidizing and reducing agents: (a) \(\mathrm{As}_{4} \mathrm{O}_{6}(s)+\mathrm{MnO}_{4}^{-}(a q) \longrightarrow \mathrm{AsO}_{4}^{3-}(a q)+\mathrm{Mn}^{2+}(a q)\) [acidic] (b) \(\mathrm{P}_{4}(s) \longrightarrow \mathrm{HPO}_{3}^{2-}(a q)+\mathrm{PH}_{3}(g)\) [acidic] (c) \(\mathrm{MnO}_{4}^{-}(a q)+\mathrm{CN}^{-}(a q) \longrightarrow \mathrm{MnO}_{2}(s)+\mathrm{CNO}^{-}(a q)\) [basic]

Balance the following skeleton reactions, and identify the oxidizing and reducing agents: (a) \(\mathrm{NO}_{2}(g) \longrightarrow \mathrm{NO}_{3}^{-}(a q)+\mathrm{NO}_{2}^{-}(a q)\) [basic] (b) \(\mathrm{Zn}(s)+\mathrm{NO}_{3}^{-}(a q) \longrightarrow \mathrm{Zn}(\mathrm{OH})_{4}^{2-}(a q)+\mathrm{NH}_{3}(g)[\mathrm{basic}]\) (c) \(\mathrm{H}_{2} \mathrm{~S}(g)+\mathrm{NO}_{3}^{-}(a q) \longrightarrow \mathrm{S}_{8}(s)+\mathrm{NO}(g)\) [acidic]

Use the following half-reactions to write three spontaneous reactions, calculate \(E_{\text {cell }}^{\circ}\) for each reaction, and rank the strengths of the oxidizing and reducing agents: (1) \(\mathrm{Au}^{+}(a q)+\mathrm{e}^{-} \longrightarrow \mathrm{Au}(s)\) \(E^{\circ}=1.69 \mathrm{~V}\) (2) \(\mathrm{N}_{2} \mathrm{O}(g)+2 \mathrm{H}^{+}(a q)+2 \mathrm{e}^{-} \longrightarrow \mathrm{N}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) \quad E^{\circ}=1.77 \mathrm{~V}\) (3) \(\mathrm{Cr}^{3+}(a q)+3 \mathrm{e}^{-} \longrightarrow \mathrm{Cr}(s) \quad E^{\circ}=-0.74 \mathrm{~V}\)

Write a balanced equation from each cell notation: (a) \(\operatorname{Mn}(s)\left|\mathrm{Mn}^{2+}(a q) \| \mathrm{Cd}^{2+}(a q)\right| \mathrm{Cd}(s)\) (b) \(\mathrm{Fe}(s)\left|\mathrm{Fe}^{2+}(a q) \| \mathrm{NO}_{3}^{-}(a q)\right| \mathrm{NO}(g) \mid \operatorname{Pt}(s)\)

What are \(E_{\text {cell }}^{\circ}\) and \(\Delta G^{\circ}\) of a redox reaction at \(25^{\circ} \mathrm{C}\) for which \(n=1\) and \(K=5.0 \times 10^{-6} ?\)
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