Question

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

• A. Aqua regia is prepared by mixing conc. $\mathrm{HCl}$ and conc. ${\mathrm{HNO}}_3$ in $3:1$ molar ratio.
• B. Reaction of gold with aqua regia produces an anion having $\mathrm{Au}$ in $+3$ oxidation state.
• C. Reaction of gold with aqua regia produces ${\mathrm{NO}}_2$ in the absence of air
• D. The yellow color of aqua regia is due to the presence of $\mathrm{NOCl}$ & ${\mathrm{Cl}}_2$.

Answer 1

Answer: (A), (B), (D)

The yellow color of aqua regia is due to the presence of $\mathrm{NOCl}$ & ${\mathrm{Cl}}_2$.

Explanation for correct options:

Options A, B, and D:

The equation is as follows:

$\mathrm{Au}\left(\mathrm{s}\right)+{\mathrm{HNO}}_3\left(\mathrm{aq}\right)+4\mathrm{HCl}\left(\mathrm{aq}\right){\to \left[{\mathrm{AuCl}}_4\right]}^{-}\left(\mathrm{aq}\right)+\left[\mathrm{NO}\right]\left(\mathrm{aq}\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

1. Conc. $\mathrm{HCl}$ and conc. ${\mathrm{HNO}}_3$ in $3:1$ molar ratio is mixed to prepare aquaregia.
2. Reaction of gold with aqua regia produces an anion having $\mathrm{Au}$ in $+3$ oxidation state.
3. The yellow color of aqua regia is due to the presence of $\mathrm{NOCl}$ & ${\mathrm{Cl}}_2$ .

Explanation of the incorrect option:

Option C:

1. Reaction of gold with aqua regia produces $\mathrm{NOCl}/\mathrm{NO}$ in the absence of air.