Aqua regia is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of ______ by volume.

3 : 1

The correct answer is option (1) 3: 1.

Aqua regia is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3: 1.

Traditionally, aqua regia is prepared by mixing three volumes of concentrated hydrochloric acid with one volume of concentrated nitric acid. This mixture is highly corrosive and is commonly used to dissolve noble metals such as gold and platinum.