What is formed by the reaction of water with sodium peroxide?

$H_2O_2$ is always stored in black bottles because

The volume strength of $8.9 \, M \, H_{2}O_{2}$ solution calculated at $273 \, K$ and $1 \, atm$ is.........
$(R = 0.0821 \, L \, atm \, K^{-1} \, mol^{-1})$ (rounded off to the nearest integer)

The oxide that gives $H_2O_2$ on treatment with a dilute acid is

Which of the following produces $H_2O_2$ on hydrolysis?

How many $mL$ of perhydrol is required to produce sufficient oxygen which can be used to completely convert $2 \ L$ of $SO_2$ gas to $SO_3$ gas (in $mL$)?