what is Aqua Regia? How does it dissolve gold?
Answers
Aqua regia is a mixture of concentrated nitric acid and concentrated hydrochloric acid. It is formed by mixing concentrated hydrochloric acid and concentrated nitric acid in 3:1 ratio. This mixture is also known as Royal water. This is a corrosive, fuming yellow or red liquid, used by jewelers to dissolves gold, platinum, etc,.
Nitric acid and hydrochloric acid cannot alone dissolve gold.
Aqua regia=Aqua regia is a very strong acid formed by the combination of concentrated nitric acid and concentrated hydrochloric acid, both of which are strong acids. It is generally used to remove metals like gold and platinum from substances, especially in microelectronics and micro-fabrications labs.
The reason aqua regia can dissolve gold (and metals like platinum and palladium) is that each of its two component acids (i.e., hydrochloric acid and nitric acid) carries out a different function. While nitric acid is an excellent oxidizing agent, the chloride ions from the HCl form coordination complexes with gold ions, thereby removing them from the solution