What is aqua regia ? Why are gold and platinum soluble in it ?

Explanation

### Step-by-Step Solution:

**Step 1: Define Aqua Regia**
Aqua regia is a highly corrosive mixture of two strong acids: hydrochloric acid (HCl) and nitric acid (HNO3). It is commonly referred to as "royal water" due to its ability to dissolve noble metals like gold and platinum.

**Step 2: Composition of Aqua Regia**
Aqua regia is prepared by mixing hydrochloric acid and nitric acid in a specific ratio. The typical ratio used is 3 parts hydrochloric acid to 1 part nitric acid by volume.

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