Question

Consider the following half-reactions:

$$\begin{gathered} \mathit{I}\mathit{r}\mathit{C}{{\mathbf{l}}_{\mathbf{6}}}^{\mathbf{3}\mathbf{-}}\mathbf{+}\mathbf{3}{\mathit{e}}^{\mathbf{-}}\mathbf{\to }\mathit{I}\mathit{r}\mathbf{+}\mathbf{6}\mathit{C}{\mathit{l}}^{\mathbf{-}}\mathbf{ }\mathbf{ }{\mathit{E}}^{\mathbf{p}}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{77}\mathbf{ }\mathit{V} \\ \mathit{P}\mathit{r}\mathit{C}{{\mathbf{l}}_{\mathbf{4}}}^{\mathbf{2}\mathbf{-}}\mathbf{+}\mathbf{2}{\mathit{e}}^{\mathbf{-}}\mathbf{\to }\mathit{P}\mathit{t}\mathbf{+}\mathbf{4}\mathit{C}{\mathit{l}}^{\mathbf{-}}\mathbf{ }\mathbf{ }{\mathit{E}}^{\mathbf{o}}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{73}\mathbf{ }\mathit{V} \\ \mathit{P}\mathit{d}\mathit{C}{{\mathbf{l}}_{\mathbf{4}}}^{\mathbf{2}\mathbf{-}}\mathbf{+}\mathbf{2}{\mathit{e}}^{\mathbf{-}}\mathbf{\to }\mathit{P}\mathit{d}\mathbf{+}\mathbf{4}\mathit{C}{\mathit{l}}^{\mathbf{-}}\mathbf{ }\mathbf{ }{\mathit{E}}^{\mathbf{o}}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{62}\mathbf{ }\mathit{V} \end{gathered}$$

A hydrochloric acid solution contains platinum, palladium, and iridium as chloro-complex ions. The solution is a constant 1.0 M in chloride ion and 0.020 M in each complex ion. Is it feasible to separate the three metalsfrom this solution by electrolysis? (Assume that 99% of metal must be plated out before another metal begins to plate out.)

Short answer

It is possible to separate these metals by electrolysis. The reduction potential in decreasing order is $Ir>Pt>Pd$.

Step-by-step solution

Possible reduction reaction for metals

The reduction reaction for iridium can be denoted as:

$IrC{l_6}^{3-}+3e^{-}\to Ir+6C{l}^{-}$

The reduction potential is 0.77 V.

The reduction reaction for platinum is expressed as:

$PtC{l_4}^{2-}+2e^{-}\to Pt+4C{l}^{-}$

The reduction potential is 0.73 V.

The reduction potential for palladium can be denoted as:

$PdC{l_4}^{2-}+2e^{-}\to Pd+4C{l}^{-}$

The reduction potential is 0.62 V.

Separating these metals from the solution

There is a possibility of separating these metals from the solution when the voltage increases due to the non-overlapping of potential value. The reduction potential in decreasing order is $Ir>Pt>Pd$.