What is the standard cell potential for a voltaic cell using the Pb2 /Pb and Mg2 /Mg half-reactions and which metal is the cathode

The  standard cell potential, E˚cell =2.234 V, Pb metal is the cathode.

Explanation:

The Half cell reactions are

Pb2+(aq) + 2e– > Pb(s) E˚ = –0.136 V

Mg2+(aq) + 2e–>Mg(s) E˚ = –2.37 V

In a voltaic cell, reduction occurs at the cathode and oxidation occurs at the anode

 Mg(s)>Mg2+(aq) + 2e–  ( anodic oxidation)

   Pb2+(aq) + 2e>  Pb(s)  ( Cathodic reduction)

We can see that Mg  has a more negative reduction potential value leading to having a low reduction potential and therefore will occur at the anode since it will be oxidized. On the other hand Pb2+ has a less negative reduction potential and therefore will have a high reduction making it to occur at the cathode and be reduced

Using  The  standard cell potential, E˚cell = E˚cathode – E˚anode

E˚cell = –0.136 - (–2.37)

E˚cell=2.234 V

particle   p is an electron and particle q is a neutron