Question

Some word/words are missing in the following statement. You are required to rewrite the statement in the correct form using the appropriate word/words: Aqua regia contains one part by volume of nitric acid and three parts by volume of hydrochloric acid.

Answer 1

• Aqua regia is used to dissolve highly inert metals like gold ($\mathbf{Au}$) and Platinum ($\mathbf{Pt}$) which does not show solubility in other acids.
• Aqua regia is mixture of Nitric acid and Hydrochloric acid.
• It contains 1 part of concentrated Nitric acid and 3 part of concentrated Hydrochloric acid.
• The reaction involving aqua regia is shown below.
  $$\begin{gathered} {\mathrm{HNO}}_3(\mathrm{conc}.)+3\mathrm{HCl}(\mathrm{conc}.)\to \mathrm{NOCl}\left(\mathrm{l}\right)+2{\mathrm{H}}_2\mathrm{O}+2\mathrm{Cl} \\ \mathrm{Nitric}\mathrm{Hydrochloric}\mathrm{Nitrosyl}\mathrm{Nascent} \\ \mathrm{acid}\mathrm{acid}\mathrm{chloride}\mathrm{chlorine} \end{gathered}$$
• Therefore, the correct form is Aqua regia contains one part by volume of concentrated Nitric acid and three parts by volume of concentrated Hydrochloric acid.