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.
