When $KMnO_4$ is reduced with oxalic acid in acidic solution,the oxidation number of $Mn$ changes from

What is the oxidation state of sulphur in oil of vitriol?

$A$ compound contains $x$,$y$,and $z$ atoms. The oxidation number of $x$ is $+3$,$y$ is $-5$,and $z$ is $+1$. The possible formula of the compound is:

In which of the following molecules or ions does sulphur have the minimum oxidation number?

In which of the following oxoacids of phosphorus is the oxidation state of phosphorus the minimum?

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