JEE Advanced 2019 · Paper 2 · Chemistry Q2

ChemistryMultiple correct+4 / -1Question 20 of 54

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

Aqua regia is prepared by mixing conc. HCl and conc.

\ce{HNO3}

in 3:1 (

v/v

) ratio

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

Reaction of gold with aqua regia produces

\ce{NO2}

in the absence of air

The yellow colour of aqua regia is due to the presence of NOCl and

\ce{Cl2}

Answer and worked solution

Official answer: A, B, D

(A) Aqua regia is conc. HCl and conc. $\ce{HNO3}$ in a 3:1 ratio by volume. True.
(B) Gold dissolves as $\ce{[AuCl4]-}$ , with Au in the +3 state. True.
(C) The nitrogen product is NO, $\ce{Au + 4H+ + NO3- + 4Cl- -> [AuCl4]- + NO + 2H2O}$ . It forms $\ce{NO2}$ only once air oxidises it. False.
(D) $\ce{3HCl + HNO3 -> NOCl + Cl2 + 2H2O}$ ; the NOCl and $\ce{Cl2}$ make it yellow. True.

(A), (B), (D)

Topics:Group 15 Oxidation number

JEE Advanced 2019 · Paper 2, Chemistry question 2