The composition of aqua-regia is

1. dil.HCl:conc. HNO₃ 3: 1
2. conc.HCl:dil. HNO₃ 3 : 1
3. conc.HCl:conc.HNO₃ 3 : 1
4. dil.HCl:dil.HNO₃ 3: 1

Correct answer: (c) conc.HCl:conc.HNO3 3 : 1 

Explanation: Aqua-regia is a freshly prepared mixture of one part of concentrated nitric acid and three parts of concentrated hydrochloric acid (ratio 1:3).

[Note: Gold and platinum are special metals that are insoluble in common reagents but soluble in aqua-regia.] 

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Updated on: 10-Oct-2022

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