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JEE Advanced 2019 · Paper 1, Chemistry question 14

At 143 K, the reaction of XeFX4\ce{XeF4} with OX2FX2\ce{O2F2} produces a xenon compound Y. The total number of lone pair(s) of electrons present on the whole molecule of Y is ______

Answer and worked solution

Official answer: 19

OX2FX2\ce{O2F2} is a powerful fluorinating agent:
XeFX4+OX2FX2→XeFX6+OX2.\ce{XeF4 + O2F2 -> XeF6 + O2}.

Lone pairs in Y = XeFX6\ce{XeF6}.

  • Xe has one lone pair (6 bond pairs + 1 lone pair, distorted octahedral).
  • Each F has 3 lone pairs: 6×3=186\times3=18.

Total: 18+1=1918+1=19.

Answer: 19