Which of the following liberates $O_2$ upon hydrolysis?

$Hydrogen$ $peroxide$ is reduced by:

Complete the following reactions:
$(i) \ O_2^{2-} + H_2O \to $
$(ii) \ O_2^- + H_2O \to $

When $CO_2$ is bubbled through a solution of barium peroxide in water:

The volume of oxygen liberated from $0.68 \ g$ of $H_2O_2$ is ............. $mL$ at $STP$.

$12 \ V \ H_2O_2$ solution contains $680 \ g \ H_2O_2$. Then $\% \ W/V$ and volume of the solution is respectively ........ and ...........