Question
What is aqua regia? How does it help in dissolving gold or platinum? Support your answer with chemical equations.
✓
Answer
A mixture of 1 part (by weight) of conc. nitric acid and 3 parts (by weight) of conc. hydrochloric acid is called aqua regia.
Conc. HCl and conc. HNO3 react to form nascent chlorine which reacts with gold or platinum to form their respective soluble chlorides.
HNO3 + 3HCl (conc.) → 2H2O + NOCI + 2(CI)
Au + 3(CI) → AuCl3 ; Pt + 4(CI) → PtCl4
Conc. HCl and conc. HNO3 react to form nascent chlorine which reacts with gold or platinum to form their respective soluble chlorides.
HNO3 + 3HCl (conc.) → 2H2O + NOCI + 2(CI)
Au + 3(CI) → AuCl3 ; Pt + 4(CI) → PtCl4
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