Which pair of metals produces the highest voltage and why

The maximum voltage can be produced in the cell which have higher difference in the electrocemical potential , in this case it would be most reactive magnesium and less reactive platinum...magnesum spontaneously gives its two electron and Pt takes its two electron.... as result generates the highest voltage

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).