Question

What is observed when nitric acid is kept in a reagent bottle for a long time?
A.Brown vapours are seen in the bottle.
B.The nitric acid turns yellowish in colour
C.The nitric acid turns black in colour
D.Both A & B

Answer 1

Hint:Nitrogen forms three oxoacids. These are
Hyponitrous acid = ${{\text{H}}_{2}}{{\text{N}}_{2}}{{\text{O}}_{2}}$
Nitrous acid = $\text{HN}{{\text{O}}_{2}}$
Nitric acid = $\text{HN}{{\text{O}}_{3}}$
Oxoacids means acid contains oxygen
In the oxoacids of nitrogen, hyponitrous acid is a weak acid and explosive in dry but stable solution. Nitrous acid is also a weak acid. It is quite unstable and exists in only dilute solution. Nitric acid is the most important acid of nitrogen. It is a stable and strong acid. It was named as aqua fortis.

Complete answer:
When nitric acid is kept in a reagent bottle for a long time it turns into the yellowish colour and brown. Colour vapour also seen in the reagent bottle.
As we know that reagent bottle trans-parts. Due to presence of sunlight nitric acid acquire yellow colour and decomposes to \[\text{N}{{\text{O}}_{2}},\text{ }{{\text{H}}_{2}}{{\text{O}}_{2}}\]
$4\text{HN}{{\text{O}}_{3}}\text{ }\xrightarrow{\text{Sunlight}}\text{HN}{{\text{O}}_{2}}+\text{2 }{{\text{H}}_{2}}\text{O}+{{\text{O}}_{2}}$
The yellow colour of acid can be removed by warming acid at $333-353\text{ K}$ and bubbling dry air through it.
As nitric acid is the strongest one it is extremely corrosive on skin and causes painful sores.
Option (D) is correct i.e. brown vapours seen in bottles as well as nitric acid turns to yellow colour.

Note:
Rather than $\text{HN}{{\text{O}}_{3}}$ acid other strong acid are ${{\text{H}}_{2}}\text{S}{{\text{O}}_{4}},\text{ HCl, HCl}{{\text{O}}_{4}}$ i.e. all per acid etc.
Nitric acid is prepared by the Ostwald process. In the Ostwald process the mixture of ammonia and air passed over the platinum gauze catalyst at 1100 K the ammonia is oxidised to nitric oxide.
\[4\text{ N}{{\text{H}}_{3}}+{{5O}_{2}}\xrightarrow[1100\text{ K}]{{{\text{P}}^{+}}}\text{ 4 NO}+6\text{ }{{\text{H}}_{2}}\text{O}\]
Further the nitric oxide is then oxidised to nitrogen dioxide by air which is cooled to 325 K and absorbed in water.
$\begin{align}
  & 2\text{ NO}+{{\text{O}}_{2}}\to 2\text{ N}{{\text{O}}_{2}} \\
 & \text{3 N}{{\text{O}}_{2}}+{{\text{H}}_{2}}\text{O}\to \text{2 H N}{{\text{O}}_{3}}+\text{NO} \\
\end{align}$
And the repulsive forces felt by valence shell electrons from the electron present in the inner shell is called shielding effect or screening effect.