The oxidation number of $N$ in $NH_4Cl$ is

Oxidation numbers of $P$ in $PO_4^{3-}$,$S$ in $SO_4^{2-}$ and that of $Cr$ in $Cr_2O_7^{2-}$ are respectively

$2.5 \ mol$ of hydrazine $(N_2H_4)$ loses $25 \ mol$ of electrons to form a new compound $X$. Assuming all lost electrons are contained in the new compound,what is the oxidation state of nitrogen in compound $X$?

What is the oxidation number of $S$ in $H_2S_2O_8$?

The oxidation number of fluorine in $F_2O$ is

Compounds having the highest oxidation state of the central atom act as acids,the lowest ones act as bases,and intermediate oxidation states act as amphoteric. Which one of the following is amphoteric?