Question

Nitrating mixture is:
$(a)$ Fuming nitric acid
$(b)$Mixture of conc ${H_2}S{O_4}$ and conc $HN{O_3}$
$(c)$ Mixture of nitric acid and anhydrous zinc chloride
$(d)$ None of the above

Answer 1

Hint – In this question use the concept that nitrating mixture is composed of nitric acid and inorganic compounds like $\left( {{H_2}S{O_4},B{F_3},{\text{ and AlC}}{{\text{l}}_3}} \right)$ as well as organic compounds. Search out for nitric acid along with the possible inorganic compounds in options that leads to formation of nitrating mixture.

Complete answer:

Nitrating mixture is a mixture of concentrated nitric acid (HNO3) or nitrogen oxides with inorganic compounds $\left( {{H_2}S{O_4},B{F_3},{\text{ and AlC}}{{\text{l}}_3}} \right)$ or organic compounds for example acetic anhydride.
And it generates the active nitrating species $N{O_2}^ + $(nitronium cation)
So nitrating mixture is conc. HNO3 + H2SO4, produces $N{O_2}^ + $ electrophile which carries out electrophilic substitution reactions.
So this is the required answer.
Hence option (B) is the correct answer.

Note – Fuming nitric acid present in option (a) is concentrated nitric acid containing dissolved nitrogen oxides prepared as either a colorless to pale yellow or a red to brown corrosive poisonous liquid and is used as an nitrating agent.