Question

The composition of aqua-regia is

• A. $\mathrm{Dil}.\mathrm{HCl}:\mathrm{Conc}.{\mathrm{HNO}}_{3}3:1$
• B. $\mathrm{Conc}.\mathrm{HCl}:\mathrm{Dil}.{\mathrm{HNO}}_{3}3:1$
• C. $\mathrm{Conc}.\mathrm{HCl}:\mathrm{Conc}.{\mathrm{HNO}}_{3}3:1$
• D. $\mathrm{Dil}.\mathrm{HCl}:\mathrm{Dil}.{\mathrm{HNO}}_{3}3:1$

Answer 1

The correct option is C

$\mathrm{Conc}.\mathrm{HCl}:\mathrm{Conc}.{\mathrm{HNO}}_{3}3:1$

The explanation for the correct answer:-

Option (C) $\mathrm{Conc}.\mathrm{HCl}:\mathrm{Conc}.{\mathrm{HNO}}_{3}3:1$

• Aqua regia is a yellow-orange or sometimes red colour fuming liquid. Aqua regia is a mixture of nitric acid and hydrochloric acid, at a molar ratio of 1:3 optimally.
• Aqua regia is mainly used for the manufacture of chloroauric acid(${\mathrm{HAuCl}}_4$).
• It can dissolve noble metals such as gold and platinum but not all metals.

The explanation for the incorrect answer:-

Option (A) $\mathrm{Dil}.\mathrm{HCl}:\mathrm{Conc}.{\mathrm{HNO}}_{3}3:1$

• Since both components in aqua regia are in concentrated form thus, this option is incorrect.

Option (B) $\mathrm{Conc}.\mathrm{HCl}:\mathrm{Dil}.{\mathrm{HNO}}_{3}3:1$

• Here in the option, Nitric acid is required in concentrated form thus, this option is incorrect.

Option (D) $\mathrm{Dil}.\mathrm{HCl}:\mathrm{Dil}.{\mathrm{HNO}}_{3}3:1$

• $\mathrm{HCl}\mathrm{and}{\mathrm{HNO}}_3$ should be concentrated in aqua regia, thus this option is incorrect.

Hence option (c) is correct.