The following cell reactions occur spontaneously: (a) Arrange the following reduction half-reactions in order of decreasing tendency to occur:

Key Concepts

Reduction Half-Reactions

Reduction half-reactions represent the gain of electrons by a species in a redox reaction. In these reactions, the species being reduced decreases its oxidation state. Understanding the specific half-reactions involved is crucial for determining their relative tendencies to occur spontaneously.

Standard Electrode Potentials

Standard electrode potentials (E°) are measured values that indicate the tendency of a half-reaction to occur as a reduction at standard conditions. A higher E° value signifies a greater tendency for the reaction to occur spontaneously. Comparing these values allows for the arrangement of half-reactions in order of their likelihood to proceed.

Spontaneity of Reactions

The spontaneity of a reaction is determined by the Gibbs free energy change (ΔG). A negative ΔG indicates that a reaction can occur spontaneously. In the context of half-reactions, the overall cell potential (E°cell) must be positive for the reaction to be spontaneous, which is derived from the difference in standard electrode potentials of the half-reactions.