In which of the following substances is the oxidation state of sulfur $-1$?

One mole of $N_2H_4$ loses $10 \ moles$ of electrons to form a new compound $Z$. Assuming that all the nitrogen atoms appear in the new compound,what is the oxidation state of nitrogen in $Z$? (There is no change in the oxidation state of hydrogen.)

The oxidation number of $Cr$ in $K_3CrO_8$ is $+5$. How many peroxy linkages are present in this molecule?

Explain the Stock notation theory with examples.

The oxidation states of $P$ in $PO_4^{3-}$,$S$ in $SO_4^{2-}$,and $Cr$ in $Cr_2O_7^{2-}$ are respectively:

What is the oxidation state of $Fe$ in $Fe_{0.94}O$?