This section focuses on the roles of electrodes, the reactions occurring in an electrochemical cell, and the concept of cell capacity.

The document defines the key components of an electrochemical cell:

Vocabulary:

• Anode: The electrode where oxidation occurs
• Cathode: The electrode where reduction occurs

When the electrodes of a cell are connected:

1. An oxidation-reduction reaction occurs in the circuit
2. Electrons move between the terminals of the cell
3. Reactants are separated

Highlight: At the negative pole, electrons arrive (reduction occurs), while at the positive pole, electrons depart (oxidation occurs).

The role of the salt bridge is explained:

Definition: The salt bridge allows ions to move, ensuring current flow and maintaining electrical neutrality of the electrolytes.

The concept of cell depletion is introduced:

Vocabulary: A cell is a system out of equilibrium and functions as long as ΔrG < K (spontaneous reaction). A depleted cell reaches equilibrium when ΔrG = K.

The document then discusses the electrical capacity of a cell:

Definition: The capacity of a cell is the electric charge that circulates during its complete functioning period, measured in Coulombs.

Example: |Q| = N × e = ne × NA × e

For constant intensity: Q = I × Δt

This final section provides an overview of common oxidizing and reducing agents, with a focus on their practical applications.

The document lists several common oxidants:

Example: Common oxidants include:

• Oxygen O₂ (O₂/H₂O couple)
• Bleach with hypochlorite ions (ClO⁻/Cl⁻ couple)
• Chlorine Cl₂ (Cl₂/Cl⁻ couple)

It also presents common reductants:

Example: Common reductants include:

• Hydrogen H₂ (H⁺/H₂ couple)
• Ascorbic acid (Vitamin C) (C₆H₆O₆/C₆H₈O₆ couple)

The document emphasizes the importance of metals as reductants:

Highlight: Metals, particularly those in Block 3 of the periodic table, are generally good reductants because they easily give up electrons.

This section provides valuable information for understanding the behavior of various substances in electrochemical reactions and their potential applications in electrochemical cells.

This section delves into the fundamental concepts of electron transfer and oxidation-reduction (redox) reactions, which form the basis of electrochemical cells.

Definition: An oxidation-reduction reaction involves the transfer of electrons between reactants.

The document introduces key terms and concepts:

Vocabulary:

• Reductant: An entity capable of donating electrons
• Oxidant: An entity capable of accepting electrons
• Oxidant/Reductant Couple: Represented by the equation Ox + ne⁻ = RED

The process of electron transfer is explained through half-equations:

Example:

• Oxidation: A half-equation modeling the loss of electrons
• Reduction: A half-equation modeling the gain of electrons

The concept of spontaneous electron transfer through an external circuit is introduced, leading to the discussion of electrochemical cells.

Highlight: Electrochemical cells facilitate spontaneous electron transfer through an external circuit.

The document then explains the constitution and functioning of electrochemical cells:

1. A cell consists of two half-cells
2. Each half-cell contains an electrolyte solution and an electrode
3. The half-cells are connected by a salt bridge

Definition: An electrolyte is a solution in which an electrode is immersed, containing the entities of an oxidation-reduction couple.

The flow of electric current in an electrochemical cell is described:

• In metal wires: Charges carried by electrons
• In solutions: Charges carried by ions
• Outside the generator: Current flows from the positive to the negative terminal

Highlight: Negative charge carriers move in the opposite direction of the electric current, while positive charge carriers move in the same direction.