What is the standard cell potential for a voltaic cell using the Pb²⁺/Pb and Mg²⁺/Mg half-reactions? Which metal is the cathode? Standard Reduction Potentials (volts) in Aqueous
Solution
$\begin{array} { l l } \mathrm { Pb } ^ { 4 + } + 2 \mathrm { e } ^ { - } \rightarrow \mathrm { Pb } ^ { 2 + } & + 1.80 \\ \mathrm { Au } ^ { 3 + } + 3 \mathrm { e } ^ { - } \rightarrow \mathrm { Au } & + 1.50 \\ \mathrm { Fe } ^ { 3 + } + 3 \mathrm { e } ^ { - } \rightarrow \mathrm { Fe } & + 0.771 \\ \mathrm { I } _ { 2 } + 2 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { I } ^ { - } & + 0.535 \\ \mathrm {~Pb} ^ { 2 + } + 2 \mathrm { e } ^ { - } \rightarrow \mathrm { Pb } & - 0.124 \\ \mathrm { Al } ^ { 3 + } + 3 \mathrm { e } ^ { - } \rightarrow \mathrm { Al } & - 1.66 \\ \mathrm { Mg } ^ { 2 + } + 2 \mathrm { e } ^ { - } \rightarrow \mathrm { Mg } & - 2.37 \\ \mathrm {~K} ^ { + } + \mathrm { e } ^ { - } \rightarrow \mathrm { K } & - 2.93 \end{array}$

Question

What is the standard cell potential for a voltaic cell using the Pb²⁺/Pb and Mg²⁺/Mg half-reactions? Which metal is the cathode? Standard Reduction Potentials (volts) in Aqueous
Solution

\begin{array} { l l } \mathrm { Pb } ^ { 4 + } + 2 \mathrm { e } ^ { - } \rightarrow \mathrm { Pb } ^ { 2 + } & + 1.80 \\ \mathrm { Au } ^ { 3 + } + 3 \mathrm { e } ^ { - } \rightarrow \mathrm { Au } & + 1.50 \\ \mathrm { Fe } ^ { 3 + } + 3 \mathrm { e } ^ { - } \rightarrow \mathrm { Fe } & + 0.771 \\ \mathrm { I } _ { 2 } + 2 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { I } ^ { - } & + 0.535 \\ \mathrm {~Pb} ^ { 2 + } + 2 \mathrm { e } ^ { - } \rightarrow \mathrm { Pb } & - 0.124 \\ \mathrm { Al } ^ { 3 + } + 3 \mathrm { e } ^ { - } \rightarrow \mathrm { Al } & - 1.66 \\ \mathrm { Mg } ^ { 2 + } + 2 \mathrm { e } ^ { - } \rightarrow \mathrm { Mg } & - 2.37 \\ \mathrm {~K} ^ { + } + \mathrm { e } ^ { - } \rightarrow \mathrm { K } & - 2.93 \end{array}

Quizplus · Accepted Answer

The standard cell potential is calculated by subtracting the reduction potential of the anode (Mg) from the cathode (Pb). E°cell = E°cathode - E°anode = (-0.124 V) - (-2.37 V) = +2.25 V. Pb is the cathode because it has a higher reduction potential than Mg.

What Is the Standard Cell Potential for a Voltaic Cell