Based on Reference Table Adv-10, Standard Electrode Potentials, which half-cell has a lower reduction potential than the standard hydrogen half-cell? 1.
Cu2+ + 2e + Cu(s)
2
Fe2+ + 2e Fe(s)
3
12(s) + 2e-21-
Cl2(g) + 2 + 2C1

The answer is a) carbon-12

And a) oxygen i believe

Answer:             1.0  × 10⁻⁵ msolution:                     as we know ph is given as,                                    ph  = -log [h⁺]and,                                    [h⁺]  =  10^-ph    (1)putting value of ph in eq. 1,                                    [h⁺]  =  10⁻⁵                                    [h⁺]  =  1.0  × 10⁻⁵ m