Décrivez la pile formée en associant les deux couples redox Fe^2+ / Fe^2 Cd^2+ / Cd et son fonct

step 1 We have two half reactions, one with cadmium and one with iron. The reduction potentials for cad

Décrivez la pile formée en associant les deux couples redox...

Décrivez la pile formée en associant les deux couples redox $\mathrm{Fe}^{2+} / \mathrm{Fe}^2 \mathrm{Cd}^{2+}$ / $\mathrm{Cd}$ et son fonctionnement : Comment est-elle constituée ? Quelle réaction s'y produit-elle quand elle débite du courant? Quelle est sa force électromotrice? Quelle est la polarité des électrodes? Laquelle est l'anode et laquelle est la cathode? Dans le circuit électrique extérieur, quel est le sens de circulation des électrons? Quel est celui du courant électrique? Quelle est la représentation symbolique conventionnelle de la chaîne électrochimique réalisée dans cette pile? Si la concentration des ions $\mathrm{Fe}^{2+}$ est 1,0 mol. $\mathrm{L}^{-1}$, à quelle condition la concentration des ions $\mathrm{Cd}^{2+}$ devrait-elle satisfaire pour que la pile fonctionne en sens opposé $\mathrm{Fe}^{2+} / \mathrm{Fe}$ devenant le couple oxydant?

Décrivez la pile formée en associant les deux couples redox $\mathrm{Fe}^{2+} / \mathrm{Fe}^2 \mathrm{Cd}^{2+}$ /
$\mathrm{Cd}$ et son fonctionnement :
Comment est-elle constituée ?
Quelle réaction s'y produit-elle quand elle débite du courant?
Quelle est sa force électromotrice?

Quelle est la polarité des électrodes? Laquelle est l'anode et laquelle est la cathode?
Dans le circuit électrique extérieur, quel est le sens de circulation des électrons? Quel est celui du courant électrique?
Quelle est la représentation symbolique conventionnelle de la chaîne électrochimique réalisée dans cette pile?
Si la concentration des ions $\mathrm{Fe}^{2+}$ est 1,0 mol. $\mathrm{L}^{-1}$, à quelle condition la concentration des ions $\mathrm{Cd}^{2+}$ devrait-elle satisfaire pour que la pile fonctionne en sens opposé $\mathrm{Fe}^{2+} / \mathrm{Fe}$ devenant le couple oxydant?

Key Concepts

Electromotive Force (EMF)

The electromotive force, or cell potential, is the voltage difference between the two electrodes of a galvanic cell when no current is flowing. It is determined by the inherent properties of the redox couples involved and can be calculated using standard electrode potentials, often adjusted by the Nernst equation to account for concentration effects. The sign and magnitude of EMF indicate the spontaneous direction of the cell reaction.

Nernst Equation and Concentration Effects

The Nernst equation provides a quantitative relationship between the cell potential, the standard electrode potentials, and the concentrations (or activities) of the redox species. It allows for the prediction of cell behavior under non-standard conditions, and determines the concentration ratios necessary for a reversal in cell operation by altering the relative driving forces of the half-cell reactions.

Electrochemical Cell Notation

Electrochemical cells are typically represented using a standard line notation that separates the anode and cathode compartments with a double vertical line, representing the salt bridge. This concise notation indicates the reactants and products at each electrode, the phase boundaries, and the overall direction of electron flow, helping to standardize communication of cell configurations.

Electron Flow vs. Conventional Current

Electron flow in an electrochemical cell always occurs from the anode to the cathode through the external circuit, which is opposite to the direction of conventional current. Conventional current, historically defined as the flow of positive charge, moves from the cathode to the anode. This distinction is important when analyzing circuit diagrams and understanding the working principles of the cell.

Electrode Polarization

In a galvanic cell, electrode polarization refers to the roles of the electrodes – the anode is where oxidation occurs and is typically assigned a negative potential relative to the cathode, where reduction occurs. This difference in potential is what drives the electron flow through the external circuit. The correct identification of which electrode acts as the anode and which as the cathode is crucial for understanding cell operation.

Redox Reactions

Redox (reduction-oxidation) reactions involve the transfer of electrons between chemical species. In the context of electrochemical cells, each half-cell reaction is separated into an oxidation half-reaction (loss of electrons) occurring at the anode and a reduction half-reaction (gain of electrons) occurring at the cathode. These reactions are fundamental in determining the cell’s operation and its electromotive force.

Galvanic Cell

A galvanic cell is an electrochemical cell that converts chemical energy into electrical energy through spontaneous redox reactions. It consists of two half-cells connected by an external circuit for electron flow and a salt bridge or porous barrier to maintain charge neutrality. One half-cell undergoes oxidation while the other undergoes reduction, allowing the net flow of electrons and generation of a potential difference.

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