Moist hydrogen cannot be dried over concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$ because:

The volume of oxygen liberated from $0.68 \mathrm{g}$ of ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$ is_____        

[MH CET 2014]

i. ${\mathrm{H}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{2}} + {\mathrm{O}}_{\mathrm{3}} \to {\mathrm{H}}_{\mathrm{2}}\mathrm{O} + 2{\mathrm{O}}_{\mathrm{2}}$

ii. ${\mathrm{H}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{2}} + {\mathrm{Ag}}_{\mathrm{2}}\mathrm{O} \to 2\mathrm{Ag} +{\mathrm{H}}_{\mathrm{2}}\mathrm{O} + {\mathrm{O}}_{\mathrm{2}}$

Role of hydrogen peroxide in the above reactions is respectively    
[AIPMT 2014]