Question

Aquaregia contains 3 parts of concentrated HCl and ____.

• A. 1 part of Conc. \(\text{HNO}_3\)
• B. 1 part of dil. \(\text{HNO}_3\)
• C. 2 parts of Conc. \(\text{HNO}_3\)
• D. 3 parts of Conc. \(\text{HNO}_3\)

Hint:

Aqua Regia ("Royal Water") is a potent mixture used to dissolve noble metals like gold. Its composition is a specific ratio of two concentrated acids:
{3 parts concentrated Hydrochloric Acid (HCl)}
{1 part concentrated Nitric Acid (\(\text{HNO}_3\))} So the ratio HCl : \(\text{HNO}_3\) is 3 : 1 by volume. The question gives 3 parts HCl, so you need 1 part conc. \(\text{HNO}_3\).

Answer 1

The Correct Option is A

Concept: Aqua regia (Latin for "royal water" or "king's water") is a highly corrosive mixture of concentrated acids, notable for its ability to dissolve noble metals like gold and platinum. Step 1: Composition of Aqua Regia Aqua regia is freshly prepared by mixing:
Concentrated nitric acid (\(\text{HNO}_3\))
Concentrated hydrochloric acid (\(\text{HCl}\)) The typical molar ratio or volume ratio is important. Step 2: The Ratio of Acids Aqua regia is conventionally prepared by mixing concentrated hydrochloric acid and concentrated nitric acid, optimally in a molar ratio of 3:1, which corresponds to a volume ratio of approximately:
3 parts of concentrated hydrochloric acid (\(\text{HCl}\))
1 part of concentrated nitric acid (\(\text{HNO}_3\)) So, for every 3 volumes of concentrated HCl, 1 volume of concentrated \(\text{HNO}_3\) is used. Step 3: Analyzing the options based on the question The question states: "Aquaregia contains 3 parts of concentrated HCl and ___ ." We need to fill in the blank regarding concentrated nitric acid. Based on the standard composition, it's 1 part of concentrated \(\text{HNO}_3\).
(1) 1 part of Conc. \(\text{HNO}_3\): Correct. This matches the 3:1 ratio of HCl to \(\text{HNO}_3\).
(2) 1 part of dil. \(\text{HNO}_3\): Incorrect. Concentrated nitric acid is used.
(3) 2 parts of Conc. \(\text{HNO}_3\): Incorrect. This would be a 3:2 ratio.
(4) 3 parts of Conc. \(\text{HNO}_3\): Incorrect. This would be a 3:3 or 1:1 ratio. Therefore, aqua regia contains 3 parts of concentrated HCl and 1 part of concentrated \(\text{HNO}_3\).