Elements which generally exhibit multiple oxidation states and whose ions are coloured are known as :

A characteristic property of transition elements.

The correct Option is "Transition metals"

Which is strongest oxidising agent?

${{\rm{F}}_2}$ is strongest oxidant among all the species.

The correct Option is "${{\rm{F}}_2}$"

Sulphur has the highest oxidation state in :

S has $ + 6$ ox. no. in ${\rm{S}}{{\rm{O}}_3}$

The correct Option is "${\rm{S}}{{\rm{O}}_3}$"

${{\rm{H}}_2}{\rm{S}}{{\rm{O}}_3}$

Nitrogen has fractional oxidation number in :

$3 \times a + 1 \times 1 = 0$,$\therefore a = - 1/3$

The correct Option is "${\rm{H}}{{\rm{N}}_3}$"

Oxidation number of $S$ in ${{\rm{S}}_2}{\rm{C}}{{\rm{l}}_2}$ is :

$2 \times a + 2 \times \left( { - 1} \right) = 0$,$\therefore a = + 1$

In which of the following $N$ has lowest oxidation number?

The correct Option is "${{\rm{N}}_2}{\rm{O}}$"

The oxidation number of $Fe$ in ${{\rm{K}}_4}{\rm{Fe}}{\left( {{\rm{CN}}} \right)_6}$ is :

$4 \times 1 + a + 6 \times \left( { - 1} \right) = 0$, $\,\therefore a = + 2$

Oxidation state of carbon in graphite is:

Graphic is uncombined state of carbon.

Which compound has oxidation number of carbon equal to zero?

$6 \times a + 12 \times 1 + 6 \times \left( { - 2} \right) = 0$ ,$\therefore a = 0$

The correct Option is "${{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}$"

Oxidation state of chromium

It is chromium peroxide. Let the oxidation number of $Cr$ is $''{x^{''}}.$ ,${\rm{C}}{{\rm{r}}^{x + }} + {\rm{O}}_2^ - + {{\rm{O}}^{2 - }} + {\rm{O}}_2^ - - {\rm{Cr}}{{\rm{O}}_5}$, $x + \left( { - 1} \right)2 + \left( { - 1} \right)2 + \left( { - 2} \right)1 = 0$,$x - 6 = 0$,$x = + 6$ Hence, the oxidation state of $Cr$ is $ + 6$.