Question

With reference to aqua regia, choose the correct option(s).

(A) The yellow colour of aqua regia is due to the presence of NOCl and Cl₂ 

(B) Aqua regia is prepared by mixing conc. HCl and conc. HNO₃ in 3 : 1 (v/v) ratio

(C)  Reaction of gold with aqua regia produces an anion having Au in +3 oxidation state

(D)  Reaction of gold with aqua regia produces NO₂ in the absence of air

Answer 1

Correct option (A, B, C) 

Explanation:

(A) HNO₃ + 3HCl → NOCl + Cl₂ + 2H₂O

The nitrosyl chloride and chlorine impart yellow color to aqua regia.

(B) Aqua regia is a 3 : 1 mixture of conc. HCl and conc. HNO₃. 

(C) Gold dissolves in aqua regia to form [AuCl₄]^–.

Au + 4H⁺ +  NO₃^- 4Cl^- → [AuCl₄]^-   + NO + 2H₂ 

(D) Air oxidises NO to NO₂.

Hence in absence of air, possibility of formation of NO₂ is less