Although it is omitted, the reaction equation for the decomposition of phosphorus pentachloride is:
PCl₅ → PCl₃ + Cl₂
The equilibrium constant's equation then becomes:
Kc = [PCl₃]*[Cl₂] / [PCl₅]
Kc = (0.02 * 0.02) / 0.0095
Kc = 0.042
The equilibrium constant is 0.042.
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