Equilibrium Constant Kp for Homogeneous Systems

The equilibrium constant Kp is a fundamental concept in chemistry, particularly for gas-phase reactions. This page provides a comprehensive overview of Kp, its calculation, and its applications.

Definition: Kp is the equilibrium constant expressed in terms of partial pressures for a reversible reaction occurring in the gas phase.

The calculation of Kp involves the partial pressures of reactants and products at equilibrium. The formula for Kp is given as:

Kp = (PC)^y × (PD)^z / (PA)^v × (PB)^w

Where P represents the partial pressure, and the exponents correspond to the stoichiometric coefficients in the balanced equation.

Vocabulary: Partial pressure is the pressure exerted by an individual gas in a mixture. It's calculated as P = mole fraction × total pressure.

An important aspect of Kp is its relationship with temperature and other factors:

Highlight: Only temperature affects the value of Kp. Pressure changes and catalysts do not influence Kp.

The page also discusses the application of Le Chatelier's Principle to the Haber Process, a significant industrial reaction for ammonia production:

N2$g$ + 3H2$g$ ⇌ 2NH3$g$ ΔH = -92kJ

Example: For the Haber Process, Kp = (PNH3)^2 / (PN2 × (PH2)^3)

Key points about this reaction:

• The Kp value is 6.0 × 10^5 at 25°C
• The forward reaction is exothermic
• Kp decreases as temperature rises (at 227°C, Kp = 0.10)
• The activation energy for the forward reaction exceeds 150kJ

Understanding these concepts is crucial for predicting and controlling chemical equilibria in various industrial and laboratory processes.