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

In which of the following compounds does nitrogen exhibit the highest oxidation state?

The correct order of the oxidation states of nitrogen in $NO$,$N_2O$,$NO_2$,and $N_2O_3$ is:

The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct?
$1$. The oxidation number of hydrogen is always $+1$.
$2$. The algebraic sum of all the oxidation numbers of all elements in a compound is zero.
$3$. An element in the free or the uncombined state bears oxidation number zero.
$4$. In all its compounds,the oxidation number of fluorine is $-1$.

The oxidation numbers of the two $Cl$ atoms in bleaching powder,$CaOCl_2$,are

Oxidation number of Nitrogen in $NH_4NO_3$ is