Write the balanced chemical equations for the following process:
(i) ${\mathrm{XeF}}_2$ undergoes hydrolysis.
(ii) ${\mathrm{MnO}}_2$ is heated with concentrated $\mathrm{HCl}$.
OR
Arrange the following in order of property indicated for each set:
(i) ${\mathrm{H}}_2\mathrm{O},{\mathrm{H}}_2\mathrm{S},{\mathrm{H}}_2\mathrm{Se},{\mathrm{H}}_2\mathrm{Te}$ - increasing acidic character.
(ii) $\mathrm{HF},\mathrm{HCl},\mathrm{HBr},\mathrm{HI}$ - decreasing bond enthalpy