Hydrolysis of peroxo-disulphuric acid $(H_2S_2O_8)$ gives

The $H-O-O$ bond angle in $H_2O_2$ is ............. $^o$

Electrolysis of $X$ gives $Y$ at anode. Vacuum distillation of $Y$ gives $H_2O_2$. The number of peroxy $(O-O)$ bonds present in $X$ and $Y$ respectively are :

$H_2O_2$ restores the color of old lead paintings,blackened by the action of $H_2S$ gas by:

The reaction $H_2S + H_2O_2 \to S + 2H_2O$ manifests

Which of the following reactions is incorrect?