Question

Fully explain why the following reaction will not occur.
Sn2+(aq)+Pb4+(aq)--> Sn(s)+Pb2+(aq)

Answer 1

You cannot get Sn2+ + Pb4+ → Sn(s) + Pb2+ because the equation violates basic redox (electron) bookkeeping: both reactants would have to be reduced (gain electrons), and there is no species available to be oxidized (to supply those electrons).

Show oxidation states and half‑reactions:
- Sn2+ → Sn(s) is a reduction: Sn2+ + 2 e− → Sn(0).
- Pb4+ → Pb2+ is also a reduction: Pb4+ + 2 e− → Pb2+.

Both half‑reactions consume electrons, so they cannot occur together without a corresponding oxidation half that produces electrons. Electrons must be conserved in any redox process.

The actual chemically reasonable redox outcome is that Pb(IV) (a strong oxidizer) oxidizes Sn(II) to Sn(IV), while Pb(IV) is reduced to Pb(II). Those half‑reactions are:
- oxidation: Sn2+ → Sn4+ + 2 e−
- reduction: Pb4+ + 2 e− → Pb2+

Net (balanced) reaction:
Sn2+ + Pb4+ → Sn4+ + Pb2+

So Sn(s) will not form from Sn2+ in the presence of Pb4+; instead Pb4+ oxidizes Sn2+ to Sn4+.