How does gold react with aqua regia?

Gold is known for its resistance to corrosion and chemical reactions, but it can be dissolved by a mixture called aqua regia. Aqua regia is a highly corrosive mixture of concentrated nitric acid (HNO3) and concentrated hydrochloric acid (HCl), usually in a ratio of 1:3.

When gold comes into contact with aqua regia, a vigorous reaction takes place. The nitric acid and hydrochloric acid in aqua regia work together to dissolve the gold. The reaction can be summarized as follows:

Au (s) + HNO3 (aq) + 3HCl (aq) → AuCl3 (aq) + NO (g) + 2H2O (l)

In this reaction, the gold (Au) reacts with nitric acid (HNO3) and hydrochloric acid (HCl) to form gold(III) chloride (AuCl3), nitrogen monoxide (NO) gas, and water (H2O). Gold(III) chloride is soluble in the solution, which gives the solution a characteristic yellowish color.

Aqua regia is one of the few substances that can dissolve gold, making it a useful tool in gold refining and analysis. However, due to its highly corrosive nature, aqua regia should be handled with extreme caution and in a well-ventilated area.