Question

For $HN{O_2}$ acts as an oxidant with which one of the following reagent:
A) $KMn{O_4}$
B) ${H_2}S$
C) ${K_2}C{r_2}{O_7}$
D) $B{r_2}$

Answer 1

An oxidant is a chemical species that removes electrons or oxidizes the other chemical species. Oxidation means the removal of electrons which can also be described as the removal of hydrogen atoms. One can think about the given reagents in options and decide which can undergo oxidation by the $HN{O_2}$.

Complete step by step answer:

1. First of all we will discuss the chemical species $HN{O_2}$. $HN{O_2}$ is called nitrous acid which typically acts as both an oxidizing agent and the reducing agent.
2. Now let us discuss the term oxidant which is a chemical species that oxidizes other chemicals by removing the electrons from other chemicals.
3. Now let's analyze the reagents in the given option and decide which can get oxidized by the oxidant $HN{O_2}$. In option A the reagent $KMn{O_4}$ does not have hydrogen atoms which can be removed to get it oxidized. Hence, this gets reduced by the $HN{O_2}$.
4. In the case of ${H_2}S$, there are two hydrogen atoms which can be removed to get it oxidized by $HN{O_2}$. Hence, $HN{O_2}$ acts as an oxidant for reagent ${H_2}S$.
5. In the case of ${K_2}C{r_2}{O_7}$ and $B{r_2}$ they both get reduced due to no presence of hydrogen atoms in their structure. Hence, they both get reduced by the $HN{O_2}$.
   Therefore, $HN{O_2}$ acts as an oxidant with a reagent ${H_2}S$ which shows option B as the correct choice.

Note:
The oxidation state number of nitrogen in $HN{O_2}$ is ${\text{ + 3}}$ which means this oxidation number can be increased or decreased which can act as both oxidizing agent and reducing agent. When the oxidation number increases it means electrons are removed from it and the $HN{O_2}$ is reduced. In case of a decrease of oxidation number, it will get oxidized which means it acts as an oxidant.