The average oxidation state of sulphur in $Na_2S_2O_3$ is:

In which of the following, the oxidation state of nitrogen is lowest?

The ionic charges of manganite and permanganate ion are respectively

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 oxidation state of oxygen in $OF_2$?

Arrange the following substances in the increasing order of the oxidation number of $Mn$: $MnCl_2, MnO_2, Mn(OH)_3, KMnO_4$.