$H_2O_2$ on reaction with $PbS$ gives

Rohan heard that instructions were given to the laboratory attendant to store a particular chemical,i.e.,keep it in the dark room,add some urea in it,and keep it away from dust. This chemical acts as an oxidising as well as a reducing agent in both acidic and alkaline media. This chemical is important for use in the pollution control treatment of domestic and industrial effluents.
$(i)$ Write the name of this compound.
$(ii)$ Explain why such precautions are taken for storing this chemical.

Which of the following can reduce the decomposition of $H_2O_2$ on exposure to light?

What is the amount of $H_2O_2$ in $gm$ present in $1 \, L$ of $1.5 \, N \, H_2O_2$ solution?

How does $H_2O_2$ behave as a bleaching agent?

Which reaction among the following gives nascent oxygen?