The composition of aqua-regia is 

Options

A. `{:(,"Dil. HCl",:,"Conc. " HNO_(3)),(," "3,:,1):}`
B. `{:(,"Dil. HCl",:,"Conc. " HNO_(3)),(," "3,:,1):}`
C. `{:(,"Conc. HCl",:,"Conc. " HNO_(3)),(," "3,:,1):}`
D. `{:(,"Dil. HCl",:,"Dil. " HNO_(3)),(," "3,:,1):}`

Explanation

**Step-by-Step Solution:**

1. **Understanding Aqua Regia**: Aqua regia is a well-known chemical mixture used in laboratories, particularly for dissolving noble metals like gold and platinum.

2. **Components of Aqua Regia**: Aqua regia is composed of two concentrated acids:
- Concentrated Hydrochloric Acid (HCl)
- Concentrated Nitric Acid (HNO3)

3. **Ratio of Components**: The specific ratio of these acids in aqua regia is crucial. It is a mixture of:
- 3 parts of concentrated HCl
- 1 part of concentrated HNO3

4. **Conclusion**: Therefore, the composition of aqua regia can be summarized as:
- 3 parts HCl : 1 part HNO3

5. **Final Answer**: The correct option that represents the composition of aqua regia is option number C (3 parts concentrated HCl and 1 part concentrated nitric acid).

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