Answer:
K = 0.5
Explanation:
Based on the reaction:
PCl₃ + Cl₂ ⇄ PCl₅
The equilibrium constant, K, is defined as:
K = P PCl₅ / P PCl₃ * P Cl₂
Where P represent the pressure at the equilibrium for each one of the gases involved in the equilibrium.
As:
P PCl₅ = 1.0atm
P PCl₃ = 1.0atm
P Cl₂ = 2.0atm
K = 1.0atm / 1.0atm * 2.0atm