Calculate the oxidation number of oxygen in potassium ozonide $(KO_3)$.

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

Assign oxidation number to the underlined elements in each of the following species:
$(a)$ $NaH_2\underline{P}O_4$
$(b)$ $NaH\underline{S}O_4$
$(c)$ $H_4\underline{P_2}O_7$
$(d)$ $K_2\underline{Mn}O_4$
$(e)$ $Ca\underline{O_2}$
$(f)$ $Na\underline{B}H_4$
$(g)$ $H_2\underline{S_2}O_7$
$(h)$ $KAl(\underline{S}O_4)_2 \cdot 12H_2O$

What is the order of the oxidation number of $S$ in $SO_3^{2-}$,$S_2O_4^{2-}$,and $S_2O_6^{2-}$?

$2$ mole of $N_2H_4$ loses $16$ mole of electrons and is converted to a new compound $X$. Assuming that all of the $N$ atoms appear in the new compound,what is the oxidation state of $N$ in $X$?

Which one of the following does not have an underlined atom with a fractional oxidation state?