Question

Select correct statement(s) regarding behavior of \[{\text{HF}}\] as non-aqueous solvent:
A.\[{\text{HCl}}\] behaves as an acid and \[{\text{HF}}\] behaves as a base.
B.\[{\text{HCl}}{{\text{O}}_4}\] behaves as a base and \[{\text{HF}}\] behaves as an acid.
C.\[{\text{HN}}{{\text{O}}_3}\] and \[{{\text{H}}_2}{\text{S}}{{\text{O}}_4}\] behaves as an base and \[{\text{HF}}\] behaves as an acid.
D.All of the above are correct statements.

Answer 1

Hint: For this question we need to know the reaction of the respective acid with \[{\text{HF}}\]. In general mineral acids dissolve in \[{\text{HF}}\] and act as base, while \[{\text{HCl}}{{\text{O}}_4}\] is amphoteric in nature with \[{\text{HF}}\].

Complete step by step answer:
Non aqueous solvents are the solvents other than water, \[{\text{HF}}\] is one such solvent. \[{\text{HF}}\] Undergo self-ionization as follows:
\[{\text{2HF}} \rightleftharpoons {\left[ {{{\text{H}}_{\text{2}}}{\text{F}}} \right]^{\text{ + }}}{\text{ + }}\,{{\text{F}}^{\text{ - }}}\]
If the given species reacts with the cationic part then that species will be termed as acid and \[{\text{HF}}\] will act as base. If the given species react with \[{{\text{F}}^ - }\] then it will act as acid and \[{\text{HF}}\] as a base. This is because \[{\text{HF}}\] is an acid while self ionization forms its conjugate base, cationic part, and conjugate acid, anionic part. The species that will react with the conjugate base will be acid obviously and the species which react with the conjugate acid will act as a base. Let us look at the reactions:
\[{\text{HN}}{{\text{O}}_3}{\text{ + HF}} \rightleftharpoons [{{\text{H}}_2}{\text{N}}{{\text{O}}_3}{\text{ }}]{{\text{ }}^ + }{\text{ + }}{{\text{F}}^ - }{\text{ }}\]
\[{\text{base acid conj base acid}}\]
Similarly sulphuric acid will react as
\[{{\text{H}}_2}{\text{S}}{{\text{O}}_4}{\text{ + HF}} \rightleftharpoons [{{\text{H}}_3}{\text{S}}{{\text{O}}_4}{\text{ }}]{{\text{ }}^ + }{\text{ + }}{{\text{F}}^ - }{\text{ }}\]
\[{\text{base acid conj base acid}}\]
But \[{\text{HCl}}{{\text{O}}_4}\] being amphoteric in nature can act as both acid and base in \[{\text{HF}}\].
\[{\text{HCl}}\] will also act as a base in \[{\text{HF}}\] with the similar reaction as shown above.

Hence from the above equation it is clear that option C is correct.

Note:
\[{\text{HF}}\] is known as hydrofluoric acid. It is mainly used in pharmaceutical industries and to prepare many organic fluorine compounds. These include polymers, fluorocarbons and refrigerants such as Freon. Mineral acids are basically the inorganic acids and the majority of them are very corrosive.