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Chapter 21: Problem 23

Why does a voltaic cell not operate unless the two compartments are connected through an external circuit?

Short Answer

Expert verified
The voltaic cell needs an external circuit to allow the flow of electrons from the anode to the cathode to generate electricity.

Step by step solution

01

- Understand the Role of Electrons

In a voltaic cell, chemical energy is converted into electrical energy through redox reactions. Electrons must flow from the anode to the cathode to produce electricity.
02

- Identify the Purpose of the External Circuit

The external circuit provides a pathway for the electrons to travel from the anode to the cathode. Without this path, the electrons cannot move, and the redox reaction cannot take place properly.
03

- Define the Electrodes' Roles

The anode is where oxidation occurs, resulting in the release of electrons. The cathode is where reduction takes place, requiring the acceptance of electrons. The movement of electrons from the anode to the cathode through the external circuit is essential for the redox reactions.
04

- Explain the Need for a Complete Circuit

For the voltaic cell to function, there must be a complete circuit, including both the external circuit for electron flow and the internal salt bridge or porous barrier for ion flow. Without the external circuit, the flow of electrons is interrupted, and thus, the cell does not generate electricity.

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Key Concepts

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

External Circuit
A voltaic cell needs an external circuit to work. The external circuit is a pathway that allows electrons to flow from the anode to the cathode. Without this pathway, there is no place for electrons to move, and the cell can't produce electricity.
Imagine it like a road: cars (electrons) need roads (external circuits) to get from one city (anode) to another city (cathode).
Without roads connecting the two cities, cars wouldn't be able to travel. So, if a voltaic cell doesn’t have an external circuit, it’s like having a car in a city with no roads leading out!
Redox Reactions
Voltaic cells work due to redox reactions. These reactions happen through the transfer of electrons. In a redox reaction, one substance loses electrons while another gains them.
This loss and gain of electrons happen in different parts of the cell. At the anode, oxidation takes place, and at the cathode, reduction occurs.
Understanding redox is crucial because it explains why a complete circuit is needed: electrons must flow for the reactions to happen continuously.
Without the flow of electrons ensured by an external circuit, these reactions would stop, and the cell would cease to function.
Anode and Cathode Roles
In a voltaic cell, there are two electrodes: the anode and the cathode. Each has a specific role:
  • Anode: This is where oxidation happens. During oxidation, the anode material loses electrons. These electrons need to go somewhere, which is where the external circuit comes in.
  • Cathode: This is where reduction occurs. Reduction is the gain of electrons. The cathode needs to receive electrons coming through the external circuit.

Without the anode losing electrons and the cathode gaining them, the cell would not produce electricity. The movement of electrons from the anode to the cathode via the external circuit is what makes the voltaic cell work.
Complete Circuit Necessity
A voltaic cell must have a complete circuit to generate electricity. This complete circuit consists of two main parts: the external circuit and an internal component (salt bridge or a porous barrier).
  • External Circuit: Allows electron flow from anode to cathode.
  • Internal Component: Balances charges by allowing ions to flow, ensuring the redox reaction keeps going.

Imagine if there was a broken section of wire in the external circuit. Electrons wouldn't be able to move from the anode to the cathode. Likewise, without ions moving through the salt bridge, the circuit would be incomplete. A complete circuit is essential for continuous electron and ion flow, ensuring the voltaic cell functions properly and generates electricity consistently.

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Most popular questions from this chapter

A voltaic cell using \(\mathrm{Cu} / \mathrm{Cu}^{2+}\) and \(\mathrm{Sn} / \mathrm{Sn}^{2+}\) half-cells is set up at standard conditions, and each compartment has a volume of \(345 \mathrm{~mL}\). The cell delivers 0.17 A for \(48.0 \mathrm{~h}\). (a) How many grams of \(\mathrm{Cu}(s)\) are deposited? (b) What is the \(\left[\mathrm{Cu}^{2+}\right]\) remaining?

A voltaic cell is constructed with an \(\mathrm{Sn} / \mathrm{Sn}^{2+}\) half- cell and a \(\mathrm{Zn} / \mathrm{Zn}^{2+}\) half-cell. The zinc electrode is negative. (a) Write balanced half-reactions and the overall cell reaction. (b) Diagram the cell, labeling electrodes with their charges and showing the directions of electron flow in the circuit and of cation and anion flow in the salt bridge.

Can one half-reaction in a redox process take place independently of the other? Explain.

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

What are \(E_{\text {cell }}^{\circ}\) and \(\Delta G^{\circ}\) of a redox reaction at \(25^{\circ} \mathrm{C}\) for which \(n=2\) and \(K=65 ?\)
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