A mercury battery uses the following electrode half-reactions: (b) Calculate ∆G° (in kilojoules) and K at 25 °C for the cell reaction.

Key Concepts

Gibbs Free Energy (∆G°)

Gibbs Free Energy (∆G°) is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure. It is crucial for determining the spontaneity of a reaction; a negative ∆G° indicates a spontaneous process, while a positive value suggests non-spontaneity. The relationship between Gibbs Free Energy and the equilibrium constant (K) is given by the equation ∆G° = -RT ln(K), where R is the universal gas constant and T is the temperature in Kelvin.

Equilibrium Constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. It provides insight into the extent of a reaction; a large K value indicates that products are favored, while a small K suggests reactants are favored. The relationship between K and Gibbs Free Energy allows for the calculation of K from ∆G° and vice versa, making it essential for analyzing electrochemical cells.

Electrode Half-Reactions

Electrode half-reactions represent the individual oxidation or reduction processes occurring at the electrodes of an electrochemical cell. Each half-reaction can be expressed in terms of the transfer of electrons, which is fundamental for calculating the overall cell reaction and its thermodynamic properties. Understanding these half-reactions is essential for determining the cell potential and subsequently calculating Gibbs Free Energy and the equilibrium constant for the entire cell reaction.