Ratio of concentrated hydrochloric acid and concentrated nitric acid in aqua regia:

Explanation:
Aqua regia is a highly corrosive mixture of concentrated hydrochloric acid (HCl) and concentrated nitric acid (HNO3). It is commonly used to dissolve gold and platinum, as well as other noble metals.

The ratio of concentrated hydrochloric acid to concentrated nitric acid in aqua regia is 3:1. This means that for every 3 parts of concentrated hydrochloric acid, there is 1 part of concentrated nitric acid.

Reasoning:
The reason for this specific ratio is due to the chemical reactions that occur when hydrochloric acid and nitric acid are combined. Aqua regia is a powerful oxidizing agent, and the concentrated nitric acid plays a crucial role in this process.

When hydrochloric acid and nitric acid are mixed, the nitric acid provides oxygen to the reaction. It reacts with the chloride ions from the hydrochloric acid to form chlorine gas (Cl2), which is a strong oxidizing agent. This chlorine gas then reacts with the noble metals, such as gold and platinum, to form soluble metal chlorides.

The excess hydrochloric acid in the mixture serves multiple purposes. It helps to dissolve the metal chlorides formed during the reaction, and it also prevents the formation of unwanted precipitates. Additionally, the hydrochloric acid helps to regenerate the chlorine gas by reacting with any excess nitric acid present.

Conclusion:
In conclusion, the ratio of concentrated hydrochloric acid to concentrated nitric acid in aqua regia is 3:1. This specific ratio is necessary for the chemical reactions to occur properly and for aqua regia to effectively dissolve noble metals.