The species that does not contain peroxide ion is

The concentration of commercial $H_2O_2$ is $3.125 \ M$,then its grade is $..........$ volume.

$10 \, mL$ of $H_2O_2$ solution $(d = 1 \, g/mL)$ when reacted with $KI$ solution produced $0.5 \, g$ of iodine. Calculate the percentage purity of $H_2O_2$ .............. $\%$

The normality of $10$ $V$ (volume) hydrogen peroxide is:

Assertion $(A)$: The colour of old lead paintings can be restored by washing them with a dilute solution of $H_2O_2$.
Reason $(R)$: Hydrogen peroxide reduces $PbS$ to $Pb$.

In $H_2O_2$ molecule,the dihedral angle between the two $O-H$ planes is ............. $^o$.