For the cell shown, the measured cell potential, E_cell, is −0.3587 V at 25 °C.

Pt(s) | H2(g,0.849 atm) | H+(aq,? M) || Cd2+(aq,1.00 M) | Cd(s)

The balanced reduction half-reactions for the cell, and their respective standard reduction potential values, E⁰, are

2H+(aq)+2e⁻⟶H2(g)  E⁰=0.00 V

Cd2+(aq)+2e⁻⟶Cd(s)  E⁰=−0.403 V

Calculate the H⁺ concentration.