When three parts of concentrated HCl and one part of concentrated HNO 3 are mixed, aqua regia is formed which is used for dissolving noble metals, e.g. gold, platinum. During dissolving metals param

Question

When three parts of concentrated HCl and one part of concentrated $HNO_{3}$ are mixed, aqua regia is formed which is used for dissolving noble metals, e.g. gold, platinum. During dissolving metals paramagnetic gas produced. Calculate mass (in gm) of paramagnetic gas produces by dissolution of 19.7 gm Au and 29.25 gm Pt metal in excess of aqua regia.

[Assume no NOCl formed in the reaction]

[Given atomic mass (in u) of N = 14, O = 16, Au = 197 , Pt = 195]

TestHub · Accepted Answer

Au + 4 H + + NO 3 − ​ + 4 Cl − → AuCl 4 − ​ + NO + 2 H 2 ​ O n NO ​ 3 Pt + 16 H + + 4 NO 3 − ​ + 18 Cl − n NO ​ wt. NO ​ ​ = 197 19.7 ​ × 1 = 0.1 → 3 PtCl 6 2 − ​ + 4 NO + 8 H 2 ​ O = 195 29.25 ​ × 3 4 ​ = 0.2 = 0.3 × 30 = 9 gm ​

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