Question

Aqua regia reacts with platinum to yield
A) \[Pt{\left( {N{O_3}} \right)_4}\]
B) \[{H_2}PtC{l_6}\]
C) \[PtC{l_4}\]
D) \[PtC{l_2}\]

Answer 1

Hint: Before starting this question we need to understand aqua regia. Aqua regia is the concentrated solution of two acids which is hydrochloric acid and nitric acid. Both acids should be in concentrated form. The nature of aqua regia is highly corrosive thus it reacts with heavy noble metals.

Complete answer:
We have to know that the aqua regia is formed by taking two acids which are concentrated hydrochloric acid and concentrated nitric acid in the molecular ratio of 3:1 that means when 3 parts of concentrated hydrochloric acid is added to one part of concentrated nitric acid then aqua regia is formed.
The reaction of aqua regia reacting with platinum metal can be represented as:
Platinum is considered to be a noble metal that can react with aqua regia solution. The product so formed on reacting aqua regia with platinum metal is nitroso platinic chloride which is formed in solid state. Further this solid compound reacts with 2 molars of hydrochloric acid to produce chloroplatinic acid and nitrosyl chloride. Further on heating chloroplatinic acid with chlorine gas we get chloroplatinic acid that is an end product for this chemical reaction.
\[Pt + {\text{ }}2HN{O_3} + 4HCl \to \left( {N{O_2}} \right)PtC{l_4} + {H_2}O + \dfrac{1}{2}{O_2}\]
\[\left( {N{O_2}} \right)PtCl4 + 2HCl \to {H_2}PtC{l_4} + NOCl\]
\[{H_2}PtC{l_4} + C{l_2} \to {H_2}PtC{l_6}\]
The reaction is taking place in three steps which are shown above and it is clearly seen from the solution that the end product is \[{H_2}PtC{l_6}\]

Thus option B) is a correct answer for this question.

Note:
We have to know that Aqua regia reacts with noble metals such as gold or platinum, even if aqua regia is highly corrosive in nature but it reacts with these metals. One must look at the complete chemical reaction taking place and then only answer the question.