Question

Write a balanced equation for the dissolution of gold in aqua regia.

A) Au + 2HNO3 + 6HCl → 3H2O + AuCl3 + 2NO
B) 2Au + 3HNO3 + 4HCl → 6H2O + 2AuCl3 + NO
C) 3Au + 4HNO3 + 6HCl → 4H2O + 3AuCl4 + NO
D) Au + HNO3 + 4HCl → 2H2O + AuCl4 + NO2

Answer 1

The balanced equation for the dissolution of gold in aqua regia is Au(s) + 4HCl(aq) + 3HNO3(aq) → HAuCl4(aq) + 3NO2(g) + 3H2O(l). Aqua regia, a mixture of concentrated nitric acid and concentrated hydrochloric acid, is able to dissolve gold due to the oxidation of gold by nitric acid and the formation of the complex ion HAuCl4.

Step-by-step explanation:

The balanced equation for the dissolution of gold in aqua regia is:

Au(s) + 4HCl(aq) + 3HNO3(aq) → HAuCl4(aq) + 3NO2(g) + 3H2O(l)

Aqua regia is a mixture of concentrated nitric acid and concentrated hydrochloric acid. The nitric acid oxidizes the gold, while the hydrochloric acid provides the chloride ions necessary to form the complex ion HAuCl4. This reaction allows gold to dissolve, making it useful for various applications.