JEE Advanced · 2019 · 27 May 2019 · Paper 2 · p-Block Elements

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

(A)Reaction of gold with aqua regia produces $NO_{2}$ in the absence of air
(B)Aqua regia is prepared by mixing conc. HCl and conc. $HNO_{3}$ in 3 : 1 (v/v) ratio✓ Correct
(C)Reaction of gold with aqua regia produces an anion having Au in +3 oxidation state✓ Correct
(D)The yellow colour of aqua regia is due to the presence of NOCl and $Cl_{2}$ ✓ Correct

Answer: (B), (C), (D)

Solution

Aqua regia is a mixture of conc. HCl and conc.

HNO_{3}

in 3:1 (v/v) ratio.

Au + HNO_{3} + 4 HCl \to AuCl_{4}^{-} + H_{3} O^{+} + NO + H_{2} O

✗

Option (D): The yellow colour is due to decomposition products NOCl (orange-yellow) and $Cl_{2}$ (greenish-yellow). ✓

Correct answers: (2), (3), (4).

JEE Advanced · 2019 · 27 May 2019 · Paper 2 · One or more correct options