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Relationship Between Kp And Kc

Easychemistry

For the gaseous equilibrium PCl₅(g) ⇌ PCl₃(g) + Cl₂(g), the values of Kp and Kc are related as:

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About This Question

Subject
chemistry
Chapter
equilibrium
Topic
relationship between kp and kc
Difficulty
Easy
Year
2025
Tags
Kp and KcGaseous EquilibriumPCl₅ Decomposition

Solution

Correct Answer:

The relationship between Kp and Kc is given by Kp = Kc(RT)^Δn, where Δn is the change in the number of moles of gaseous species (moles of gaseous products − moles of gaseous reactants) and R is the gas constant (0.0821 L atm K⁻¹ mol⁻¹). For the decomposition of PCl₅: Δn = (1 + 1) − 1 = 1. Therefore, Kp = Kc(RT)¹ = Kc(RT). Since Δn > 0, Kp is greater than Kc at all temperatures above 0 K. This equation follows from the ideal gas law relating partial pressures to molar concentrations through PV = nRT, giving P = (n/V)RT = cRT.

This easy difficulty chemistry question is from the chapter equilibrium, covering the topic of relationship between kp and kc. It appeared in the 2025 exam.

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