Use the data in Appendix B to calculate ∆G for the decom-position of nitrosyl chloride at 25 °C when the partial pressures are 2.00 atm of NOCl, 1.00 * 10^-3 atm of NO, and 1.00 * 10^-3 atm of Cl2: Is the reaction spontaneous in the forward or the reverse direction under these conditions?

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 used to predict the spontaneity of a reaction: if ∆G is negative, the reaction is spontaneous in the forward direction; if positive, it is spontaneous in the reverse direction.

Equilibrium Constant (K)

The equilibrium constant (K) is a dimensionless value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. It is related to Gibbs Free Energy by the equation ∆G = ∆G° + RT ln(Q), where Q is the reaction quotient. Understanding K helps determine the direction of spontaneity based on the current conditions.

Reaction Quotient (Q)

The reaction quotient (Q) is a measure of the relative amounts of products and reactants present in a reaction at any point in time, calculated using the same expression as K but with current concentrations or partial pressures. Comparing Q to K allows us to predict the direction in which a reaction will proceed to reach equilibrium, indicating whether the forward or reverse reaction is favored.