Aqua regia is a highly corrosive mixture of concentrated nitric acid and hydrochloric acid. It is a powerful oxidizing agent, which means it is capable of oxidizing other substances. The power of this oxidizing agent is due to the presence of free chlorine and nitrosyl chloride in the mixture. Let's break down the answer into headings and HTML bullet points for better understanding:

Components of Aqua Regia:
- Aqua regia is a mixture of concentrated nitric acid (HNO3) and hydrochloric acid (HCl).
- The concentration of both acids varies, but typically it is a 3:1 mixture of HCl and HNO3.

Oxidizing Properties:
- Aqua regia is a powerful oxidizing agent because it contains free chlorine (Cl) and nitrosyl chloride (NOCl) in the mixture.
- Nitric acid is a strong oxidizing agent, while hydrochloric acid is a strong reducing agent.
- When mixed together, they react to form chlorine and nitrosyl chloride, which are even stronger oxidizing agents than the individual acids.

Reaction Mechanism:
- When aqua regia is added to a substance, it reacts with the substance to form chlorine gas (Cl2) and nitrosyl chloride gas (NOCl).
- The chlorine gas oxidizes the substance by removing electrons, while the nitrosyl chloride oxidizes the substance by adding oxygen atoms.

Applications:
- Aqua regia is commonly used in the extraction and purification of gold and platinum.
- It is also used in the analysis of metals and minerals.
- However, due to its highly corrosive nature, it must be handled with extreme caution and only by trained professionals.

In conclusion, aqua regia is a powerful oxidizing agent due to the presence of free chlorine and nitrosyl chloride in the mixture. Its oxidizing properties make it useful in a variety of applications, but it must be handled with care due to its corrosive nature.