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

With reference to aqua regia, choose the correct option(s).
  1. Reaction of gold with aqua regia produces NO2 in the absence of air
  2. Aqua regia is prepared by mixing conc. HCl and conc. HNO3 in 3 :1v/v ratio
  3. Reaction of gold with aqua regia produces an anion having Au in +3 oxidation state
  4. The yellow colour of aqua regia is due to the presence of NOCl and Cl2

Solution

Aqua regia is 3 parts \(\mathrm{HCl}\) and 1 part \(\mathrm{HNO}_3\) \(\begin{aligned} & 3 \mathrm{HCl}+\mathrm{HNO}_2 \rightarrow \underset{\text { (Yellow colour is due to } \mathrm{NOCl} \text { and } \mathrm{Cl}_2 \text {) }}{\mathrm{NOCl}+\mathrm{Cl}_2+2 \mathrm{H}_2 \mathrm{O}} \\ & \mathrm{Au}+\text { Aqua Regia } \rightarrow \underset{(+30 . S \text { of Au})}{[\mathrm{AuCl}_4]^-} \end{aligned}\) \(\mathrm{Au}+4 \mathrm{H}^{+}+\mathrm{NO}_3^{-} 4 \mathrm{Cl}^{-} \rightarrow\left[\mathrm{AuCl}_4\right]^{-}+\mathrm{NO}+2 \mathrm{H}_2\)

Asked in: JEE Advanced 2019 (Paper 2)

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