Most Important Selected Qs for JEE AdvancedChemistryp Block Elements (Group 15, 16, 17 & 18)
With reference to aqua regia, choose the correct option(s).
Options
- AThe yellow colour of aqua regia is due to the presence of NOCl and Cl ₂
- BAqua regia is prepared by mixing conc. HCl and conc. HNO ₃ in 3: 1 (v/v) ratio
- CReaction of gold with aqua regia produces an anion having Au in +3 oxidation state
- DReaction of gold with aqua regia produces NO ₂ in the absence of air
Correct answer
C. Reaction of gold with aqua regia produces an anion having Au in +3 oxidation state
Step-by-step solution
Answer (A, B, C) (A) HNO ₃+3 HCl NOCl + Cl ₂+2 H ₂ O The nitrosyl chloride and chlorine impart yellow color to aqua regia. (B) Aqua regia is a 3: 1 mixture of conc. HCl and conc. HNO ₃ . (C) Gold dissolves in aqua regia to form [ AuCl ₄ ]⁻ . Au +4 H ⁺+ NO ₃⁻+4 Cl ⁻ [ AuCl ₄ ]⁻+ NO +2 H ₂ O (D) Air oxidises NO to NO ₂ . Hence in absence of air, possibility of formation of NO ₂ is less.