Q. For the gas phase reaction, PCl₅(g) ⇌ PCl₃(g) + Cl₂(g), which of the following conditions is correct?
A) ∆H > 0 and ∆S < 0
B) ∆H = 0 and ∆S < 0
C) ∆H > 0 and ∆S > 0
D) ∆H < 0 and ∆S < 0
Explanation
[Solution from source] Dissociation of PCl₅ breaks P–Cl bonds, so it absorbs heat (∆H > 0). One mole of gas gives two moles of gas, so disorder increases (∆S > 0). A negative ∆S would require fewer gas molecules on the product side. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.