Royal water
Aqua regia dissolves gold.
A hard-to-dissolve metal
Gold does not dissolve in hydrochloric acid, and it does not dissolve in nitric acid.
Can any liquid dissolve gold?
What this lesson covers
The idea
Aqua regia is a freshly prepared 3:1 mixture of concentrated hydrochloric acid and concentrated nitric acid; it can dissolve gold and platinum, though neither acid alone can dissolve gold.
A hard-to-dissolve metal
Gold does not dissolve in hydrochloric acid, and it does not dissolve in nitric acid.
Can any liquid dissolve gold?
- Yes, a special mixture of two acids
- No, nothing can dissolve gold
- Yes, plain water
Make the mixture
Press Next step.
A royal mixture
Aqua regia means 'royal water' in Latin. It is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1. It can dissolve gold and platinum, even though neither acid can dissolve gold alone. It is a highly corrosive, fuming liquid.
Aqua regia is a freshly prepared 3:1 mixture of concentrated hydrochloric acid and concentrated nitric acid; it can dissolve gold and platinum, though neither acid alone can dissolve gold.
Notes
Aqua regia: freshly prepared 3:1 concentrated HCl and HNO₃; dissolves gold and platinum, which neither acid does alone.
Check yourself
Aqua regia is a mixture of ...
In what ratio are the two acids mixed?
Suppose 12 equal parts of aqua regia are made in the ratio 3:1 (an example). How many parts are concentrated hydrochloric acid?
Answer: 9
3 + 1 = 4 shares of 3 parts each in 12 parts. Hydrochloric acid has 3 shares: 3 × 3 = 9 parts (nitric acid has 3 parts).
Which metals can aqua regia dissolve?
- concentrated hydrochloric acid and concentrated nitric acid — correct. Yes!
- dilute sulphuric acid and water. Dilute sulphuric acid is used in anodising; aqua regia is made from hydrochloric and nitric acids.
- sodium hydroxide and water. Aqua regia is made from two acids, not from a base.
- 1:3, hydrochloric acid to nitric acid. The ratio is 3 parts hydrochloric acid to 1 part nitric acid.
- 3:1, hydrochloric acid to nitric acid — correct. Yes!
- 1:1. The ratio in the book is 3:1, not equal parts.
- Only copper. The book says aqua regia is one of the few reagents able to dissolve gold and platinum.
- None of the metals. Aqua regia can dissolve gold and platinum.
- Gold and platinum — correct. Yes!