Q1. which reaction represents the half-reaction of lead (pb) and the srp value that could be found on an electric potential table?
q2.which value represents the standard cell potential of the spontaneous overall reaction?

The reaction that represents the half-reaction of lead Pb is    
    Pb2+(aq) + 2e- → Pb(s)   
and the SRP value on electric potential table is -0.13V.

To find the overall potential of a reaction, two half reactions can be added
together:
Oxidation:           Fe(s) → Fe2+(aq) + 2e-                               +0.44V
Reduction:          Pb2+(aq) + 2e- → Pb(s)                               - 0.13 V      
Overall reaction: Fe(s) + Pb2+(aq) → Pb(s) + Fe2+(aq)         +0.31V

This positive voltage for the overall reaction is spontaneous.

Both models are effective because they show the valence electrons, and these valence electrons indicate the reactivity of an element.

257 grams h2o i think