Aqua regia , which is used for dissolving noble metals like gold and plantium etc. is

Options

A. `1 : 3` mixture of conc. HCl and conc. `HNO_(3)`
B. `3:1` mixture of conc. HCl and conc. `HNO_(3)`
C. `1 :1` mixture of conc. HCl and conc. `HNO_(3)`
D. `3 :1` mixture of dil. `HCl` and conc. `HNO_(3)`

Answer

To solve the question about aqua regia, we need to identify the correct composition of this solution used for dissolving noble metals like gold and platinum.

### Step-by-Step Solution:

1. **Understanding Aqua Regia**: Aqua regia is a highly corrosive mixture of acids that can dissolve noble metals such as gold and platinum. It is important to note that it is not a single acid but a combination of two acids.

2. **Identifying the Components**: The two acids that make up aqua regia are concentrated hydrochloric acid (HCl) and concentrated nitric acid (HNO3).

3. **Determining the Ratio**: The key to answering the question is knowing the correct ratio of these two acids in aqua regia. Aqua regia is typically prepared in a specific ratio of HCl to HNO3.

4. **Correct Ratio**: The commonly accepted ratio for aqua regia is 3 parts of concentrated HCl to 1 part of concentrated HNO3. This means for every 3 volumes of HCl, there is 1 volume of HNO3.

5. **Conclusion**: Based on the above information, the correct answer to the question is that aqua regia is a 3:1 mixture of concentrated hydrochloric acid (HCl) and concentrated nitric acid (HNO3).

### Final Answer:
Aqua regia, which is used for dissolving noble metals like gold and platinum, is a **3:1 mixture of concentrated HCl and concentrated HNO3**.

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