Consider this reaction occurring at 298 K: N₂O(g) + NO₂(g) ⇌ 3 NO(g) b. If a reaction mixture contains only N₂O and NO₂ at partial pressures of 1.0 atm each, the reaction will be spontaneous until some NO forms in the mixture. What maximum partial pressure of NO builds up before the reaction ceases to be spontaneous?

Key Concepts

Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change. In the context of the given reaction, if the concentration of reactants (N2O and NO2) is altered, the system will adjust to either produce more products (NO) or revert to reactants to restore equilibrium.

Gibbs Free Energy

Gibbs Free Energy (G) is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure. A reaction is spontaneous when the change in Gibbs Free Energy (ΔG) is negative. The relationship between the partial pressures of the gases and ΔG can help determine the maximum pressure of NO before the reaction ceases to be spontaneous.

Equilibrium Constant (Kp)

The equilibrium constant (Kp) for a reaction at a given temperature is the ratio of the partial pressures of the products raised to their stoichiometric coefficients to the partial pressures of the reactants raised to their coefficients. For the reaction provided, Kp can be calculated using the partial pressures of N2O, NO2, and NO, allowing us to find the maximum partial pressure of NO that can exist before the reaction reaches equilibrium and becomes non-spontaneous.