Question

What is aqua regia? State which component is the oxidising agent in aqua regia.

Answer 1

• Aqua regia is a mixture consisting of 1 part of Nitric acid (concentrated) and 3 parts of Hydrochloric acid (concentrated).
• The chemical reaction is,
  $$\begin{gathered} {\mathrm{HNO}}_3\left(l\right)+3\mathrm{HCl}\left(l\right)\to \mathrm{NOCl}\left(l\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+2\mathrm{Cl}\left(g\right) \\ \mathrm{Nitric}\mathrm{Hydrochloric}\mathrm{Nitrosyl}\mathrm{Water}\mathrm{Chlorine} \\ \mathrm{Acid}\mathrm{Acid}\mathrm{chloride} \end{gathered}$$
• An oxidizing agent in a redox chemical equation is the one that oxidises other compounds to form a product and itself get reduced.
• Here, Nitric acid is the oxidising agent which oxidises Hydrochloric acid to form Chlorine.
• Therefore, Nitric acid is the oxidizing agent in aqua regia.