# Which of the following is a true peroxide?A. ${\rm{S}}{{\rm{O}}_{\rm{2}}}$ B. ${\rm{Ba}}{{\rm{O}}_{\rm{2}}}$ C. ${\rm{Mn}}{{\rm{O}}_{\rm{2}}}$ D. ${\rm{N}}{{\rm{O}}_{\rm{2}}}$

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Hint: Peroxides are a category of compounds possessing the structure ${\rm{R - O - O - R}}$, where R represents an element. The group having a single bond linkage between two oxygen atoms in peroxide is known as the peroxide group or peroxo group.

Complete Step by Step Solution:
The peroxide ion, ${\rm{O}}_{\rm{2}}^{{\rm{2 - }}}$ possesses an oxygen-oxygen covalent bond and an oxidation state of −1 for each of the oxygen atoms. The peroxide ion is a strong hydrogen ion acceptor, so the peroxides of the alkali metals and alkaline earth metals are strong bases.

We have to find the true peroxide out of the following compounds.
A. ${\rm{S}}{{\rm{O}}_{\rm{2}}}$
This is sulphur dioxide.
The oxidation state of oxygen in this compound is -2.
The oxidation state of sulphur is +4.
So, this is not peroxide.

B. ${\rm{Ba}}{{\rm{O}}_{\rm{2}}}$
This is barium peroxide.
The oxidation state of each oxide ion is -1 on each oxygen atom.
So, barium peroxide is a true peroxide.
Therefore, B is correct.

C. ${\rm{Mn}}{{\rm{O}}_{\rm{2}}}$
It is manganese dioxide.
The oxidation state of each oxide ion is -2.
So, this is not peroxide.
Thus, C is incorrect.

D. ${\rm{N}}{{\rm{O}}_{\rm{2}}}$
It is nitrogen dioxide. The oxidation state of oxygen is -2.
So, this is not peroxide.
Therefore, this option is incorrect.
So option B is correct.

Additional Information: The largely widespread peroxide is hydrogen peroxide (${{\rm{H}}_{\rm{2}}}{{\rm{O}}_{\rm{2}}}$) also called peroxide.
The other types of peroxide include the following:-
1) Peroxy acids are the peroxy derivatives of several common acids.
Examples are peroxymonosulfuric acid and peracetic acid, etc.
2) Compounds of the main group peroxide with the linkage ${\rm{M - O - O - M}}$ where M is the main group element.
3) Metal peroxides like barium peroxide, sodium peroxide and zinc peroxide.
4) Organic peroxides are compounds with the linkage ${\rm{C - O - O - C}}$ or ${\rm{C - O - O - H}}$. For example, tert-butyl hydroperoxide.

Note: In the peroxide compounds, single oxygen atoms have a -1 oxidation state. So, out of the given options only barium peroxide has this oxidation state for oxygen. Therefore, barium peroxide is a true peroxide.