Question

Hydrolysis of XeF₆

Answer 1

Both XeF4 and XeF6 hydrolyze in water to produce aqueous solutions of nonvolatile XeO3 molecules. These solutions are stable, but they are strongly oxidizing, rapidly liberating chlorine from strong HCl. The Xe-Xe(VI) potential is estimated to be 1.8 v. in acid and 0.9 v. in base. The XeO3 molecule is a weak acid, forming HXeO4- above pH 10.5. In strongly basic solution Xe(VI) disproportionates to give xenon gas and octavalent xenon, while in such solutions ozone oxidizes Xe(VI) nearly quantitatively to Xe(VIII). Sodium and barium salts of Xe(VIII), perxenates, have been characterized, with typical compositions Na4XeO6·2.2H2O and Ba2XeO6·1.5H2O. A salt of mixed oxidation state, K4XeO6·2XeO3, has also been observed. Aqueous solutions of sodium perxenate evolve oxygen slowly to give Xe(VI). The reaction becomes almost instantaneous below pH 7. Octavalent xenon is an extremely powerful oxidizing agent, rapidly oxidizing iodate to periodate and Mn+2 to permanganate. The Xe(VI)-Xe(VIII) potential is estimated at 3.0 v. in acid and 0.9 v. in base. In basic solution Xe(VIII) is present as the ion HXeO5-3. Below pH 10 the principal species becomes H2XeO6-2. Both Xe(VI) and Xe(VIII) have characteristic, pH-dependent, ultraviolet absorption spectra which can be attributed to the several species present.