Question

In the reaction: \[ \text{Pt} + 3:1 \,\text{mixture of} \,(\text{conc. HCl} + \text{conc. HNO}_3) \rightarrow [\text{X}]^{2-}, \] What is the oxidation state of Pt in the complex ion \([X]^{2-}\)?

• A. \(+2\)
• B. \(+3\)
• C. \(+4\)
• D. \(+6\)

Hint:

Platinum commonly forms complexes in \(+2\), \(+4\), and \(+6\) oxidation states, but in aqua regia, it typically forms a \(+4\) state in complex ions.

Answer 1

The Correct Option is C

Step 1: Reaction of Platinum with Aqua Regia - The platinum metal reacts with a mixture of concentrated hydrochloric acid (HCl) and concentrated nitric acid (HNO\(_3\)), known as aqua regia. - Aqua regia is a strong oxidizing agent and helps dissolve platinum, forming a platinum complex. 

Step 2: Determining the Oxidation State of Pt - In the complex ion \([X]^{2-}\), platinum typically assumes an oxidation state of \(+4\) when it reacts with aqua regia. Hence, the oxidation state of Pt in \([X]^{2-}\) is \(+4\).