Question:

What is Aqua Regia? What happens when aqua regia reacts with (i) Gold, and (ii) Platinum.

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The name “Aqua Regia” means “Royal Water” because of its ability to dissolve noble metals like gold and platinum.
Updated On: Oct 7, 2025
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Solution and Explanation

Step 1: Definition of Aqua Regia.
Aqua regia is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. It is a powerful oxidizing and dissolving medium, capable of dissolving noble metals like gold and platinum. Step 2: Reaction with Gold.
Gold dissolves in aqua regia forming chloroauric acid. \[ Au + HNO_3 + 4HCl \longrightarrow H[AuCl_4] + NO + 2H_2O \] Step 3: Reaction with Platinum.
Platinum dissolves in aqua regia forming chloroplatinic acid. \[ Pt + 4HNO_3 + 6HCl \longrightarrow H_2[PtCl_6] + 4NO_2 + 4H_2O \] Conclusion:
Aqua regia is a unique mixture that dissolves even noble metals like gold and platinum, which do not react with single acids.
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