At 200°C, PCl₅ dissociates as follows: PCl₅(g) ⇌ PCl₃(g) + Cl₂(g). It was found that the equilibrium — Chemical Equilibrium Chemistry Question
Question
At 200°C, PCl₅ dissociates as follows: PCl₅(g) ⇌ PCl₃(g) + Cl₂(g). It was found that the equilibrium vapours are 62 times as heavy as hydrogen. The percentage dissociation of PCl₅ at 200°C is
Answer: D
💡 Solution & Explanation
Molar mass of PCl₅ = 31 + 5(35.5) = 208.5. The average molar mass of the equilibrium mixture = 62 × 2 = 124. Degree of dissociation α = (M_theoretical - M_avg) / M_avg = (208.5 - 124) / 124 = 84.5 / 124 ≈ 0.6814. The percentage dissociation is 68.1%. Therefore, correct answer is D.
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