Question

Secondary nitro compounds when react with ${\text{HN}}{{\text{O}}_{\text{2}}}$ forms crystalline solids which one on treatment with ${\text{NaOH}}$ gives
A) Red solution
B) Blue solution
C) White precipitate
D) Yellow colouration

Answer 1

We must have known that Arrhenius is one of the concepts for acid and bases. Swedish chemist Arrhenius is the world's first chemist to talk about acid and bases. Depending on his concept and limitations later so many concepts are developed. Even Arrhenius is the birthplace of the concept of acids and bases. Followed by Arrhenius chemist the concept of acids and bases discuss Bronsted and Lowry in the world.

Complete answer:
According to the Arrhenius concept one substance said to acid means, acid is nothing but a substance that dissociates to give hydrogen ion when decomposed in the water. Examples of Arrhenius acids are hydrochloric acid (${\text{HCl}}$), sulphuric acid (${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$), nitrous acid (${\text{HN}}{{\text{O}}_{\text{2}}}$) etc,.
According to Arrhenius concept one substance said to base means, bases is nothing but a substance that dissociates to give hydroxyl ion when decomposed in water. Examples of Arrhenius bases are sodium hydroxide (${\text{NaOH}}$), calcium hydroxide (${\text{Ca(OH}}{{\text{)}}_{\text{2}}}$) etc,.
Hence, ${\text{HN}}{{\text{O}}_{\text{2}}}$ is acid and ${\text{NaOH}}$ is base.
The molecular formula of Secondary nitro compound is ${{\text{(R)}}_{\text{2}}}{\text{CH - N}}{{\text{O}}_{\text{2}}}$.
Secondary nitro compounds when react with ${\text{HN}}{{\text{O}}_{\text{2}}}$ and ${\text{NaOH}}$ reaction is given below,
${{\text{(R)}}_{\text{2}}}{\text{CH - N}}{{\text{O}}_{\text{2}}}\underrightarrow {{\text{HN}}{{\text{O}}_{\text{2}}}}{{\text{(R)}}_{\text{2}}}{\text{C(NO}}){\text{ - N}}{{\text{O}}_{\text{2}}}\xrightarrow{{NaOH}}{\text{Bluesolution}}$
According to the above reaction, we conclude is secondary nitro compounds when react with${\text{HN}}{{\text{O}}_{\text{2}}}$ forms crystalline solids which one on treatment with${\text{NaOH}}$ gives blue solution.

Hence, option B is the correct answer.

Note:
In generally, pH values of all acids are in between ${\text{0}}{\text{.9}}$-$6.9$ and all the bases are in between$7.1 - 14.0$. But, Arrhenius theory has some limitations. One of the main limitations is not being able to explain the behaviour of acids and bases in non-aqueous solvents such as acetone etc,. It is not able to explain the acid which doesn't contain hydrogen and bases don’t contain hydroxyl ion in the formula. Ammonia is a well known base and is not accepted as base in Arrhenius base. These limitations are recovered by further coming theories like the Bronsted and Lowry concept of acids and bases.