Answer: PCl 5 has an accessible P centre; SF 6 's S is sterically shielded by 6 F atoms preventing water attack.
- A PCl<sub>5</sub> has an accessible P centre; SF<sub>6</sub>'s S is sterically shielded by 6 F atoms preventing water attack
- B SF<sub>6</sub> is actually an ionic compound that strongly resists hydrolysis in water according to most researchers
- C PCl<sub>5</sub> is supposedly thermodynamically more stable than SF<sub>6</sub> toward hydrolysis in the majority of cases studied
- D The difference arises mainly from the temperature of the water sample used as widely reported in standard practice
Correct answer: A. PCl<sub>5</sub> has an accessible P centre; SF<sub>6</sub>'s S is sterically shielded by 6 F atoms preventing water attack
Explanation: SF<sub>6</sub>'s central S is completely surrounded by 6 F atoms; there is no accessible site for water to attack. PCl<sub>5</sub> readily hydrolyses because P can expand its coordination.
Xenon tetrafluoride (XeF4) has six electron domains around xenon — four Xe–F bonds plus two lone pairs. The lone pairs occupy opposite axial positions, leaving the four fluorine atoms in a square-planar shape (Xe–F ≈ 194 pm). Image: ChemSim, Public Domain, via Wikimedia Commons.
Concept context
Covers the nitrogen family (Group 15), oxygen family (Group 16), halogens (Group 17), and noble gases (Group 18). One of the highest-weightage inorganic chapters in NEET and JEE - includes preparation and properties of HNO₃, H₂SO₄, interhalogens, and xenon compounds.