Consider the following half-reactions: Pt^2++2 e^- ⟶Pt ℰ^∘=1.188 V PtCl4^2-+2 e^-

step 1 The simple answer to this is that the cell potential for platinum dissolving in aqua regia is po

Consider the following half-reactions: Pt^2++2 e^- ⟶Pt ...

Consider the following half-reactions: $\begin{aligned} \mathrm{Pt}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Pt} & & & \mathscr{E}^{\circ}=1.188 \mathrm{V} \\ \mathrm{PtCl}_{4}^{2-}+2 \mathrm{e}^{-} \longrightarrow & \mathrm{Pt}+4 \mathrm{Cl}^{-} & & \mathscr{E}^{\circ}=0.755 \mathrm{V} \\ \mathrm{NO}_{3}^{-}+4 \mathrm{H}^{+}+3 \mathrm{e}^{-} & \longrightarrow \mathrm{NO}+2 \mathrm{H}_{2} \mathrm{O} & & \mathscr{E}^{\circ}=0.96 \mathrm{V} \end{aligned}$ Explain why platinum metal will dissolve in aqua regia (a mixture of hydrochloric and nitric acids) but not in either concentrated nitric or concentrated hydrochloric acid individually.

Consider the following half-reactions:
$\begin{aligned}
\mathrm{Pt}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Pt} & & & \mathscr{E}^{\circ}=1.188 \mathrm{V} \\
\mathrm{PtCl}_{4}^{2-}+2 \mathrm{e}^{-} \longrightarrow & \mathrm{Pt}+4 \mathrm{Cl}^{-} & & \mathscr{E}^{\circ}=0.755 \mathrm{V} \\
\mathrm{NO}_{3}^{-}+4 \mathrm{H}^{+}+3 \mathrm{e}^{-} & \longrightarrow \mathrm{NO}+2 \mathrm{H}_{2} \mathrm{O} & & \mathscr{E}^{\circ}=0.96 \mathrm{V}
\end{aligned}$
Explain why platinum metal will dissolve in aqua regia (a mixture of hydrochloric and nitric acids) but not in either concentrated nitric or concentrated hydrochloric acid individually.

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Key Concepts

Standard Reduction Potentials

This concept involves the measured tendency of a chemical species to be reduced, which is quantified by its standard reduction potential. These potentials help predict the direction of electron flow in redox reactions and determine which species will be oxidized or reduced under given conditions.

Redox Chemistry

Redox reactions involve the transfer of electrons between species, where oxidation (loss of electrons) and reduction (gain of electrons) occur simultaneously. Understanding redox processes is key to analyzing how different reagents interact, especially in systems that involve multiple simultaneous reactions.

Synergistic Effects of Mixed Reagents

When two or more reagents are combined, as in mixtures of acids, their combined chemical behavior can produce effects that are not observed when each is used separately. This synergy can alter reaction pathways and energetics, leading to the oxidation or dissolution of substances that might remain inert when exposed to the individual components.

Complex Ion Formation

The formation of complex ions can stabilize certain oxidation states of metals once they are oxidized. In redox systems, the presence of ligands that form stable complexes with the oxidized metal can shift equilibrium, thereby promoting dissolution and altering the overall reaction energetics.

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