What is the composition of aqua regia?

1:3 of HNO₃ and HCl

The answer is 1. 1:3 of HNO₃ and HCl.

Aqua regia is a mixture of concentrated nitric acid (HNO₃) and hydrochloric acid (HCl) in a volume ratio of 1:3. It is a highly corrosive liquid that can dissolve many metals, including gold and platinum.

The nitric acid in aqua regia oxidizes the metal, while the hydrochloric acid dissolves the resulting metal ions. The reaction is exothermic, meaning that it releases heat.

Aqua regia was first described by the alchemists in the 13th century. It was used to dissolve gold, which was then called "royal metal". The name aqua regia comes from the Latin words aqua, meaning "water", and regia, meaning "royal".

So the composition of aqua regia is 1 part concentrated nitric acid to 3 parts concentrated hydrochloric acid.