${\mathrm{XeF}}_6$ on partial hydrolysis with water produces a compound, ‘X’. The same compound ‘X’ is formed when ${\mathrm{XeF}}_6$ reacts with silica. The compound ‘X’ is:

Partial hydrolysis of XeF₆​ gives XeOF_4​ (compound X)
XeF_6​ + H₂​O → XeOF₄​ (X)+ 2HF 

XeF_6​ reacts with silica SiO₂​ to form XeOF₄​ (compound X)
2XeF₆​ + SiO₂​→2XeOF₄​ (X)_​ + SiF₄​