Phosphorus pentachloride

The last element of the $$p$$-block in 6 th period is represented by the outer most electronic configuration.

A Lewis acid '$$X$$' reacts with $$\mathrm{LiAlH}_4$$ in ether medium to give a highly toxic gas. This gas when heated with $$\mathrm{NH}_3$$ gives a compound commonly known as inorganic benzene. The gas is

0.1 mole of $$\mathrm{XeF}_6$$ is treated with $$1.8 \mathrm{~g}$$ of water. The product obtained is