A galvanic cell is based on the following half-reactions: Fe²⁺ + 2e-→ Fe(s) Eº = -0.440 V 2H⁺ + 2e-→ H₂(g) Eº = 0.000 V where the iron compartment contains an iron electrode and [Fe²⁺] = 1.00 × 10⁻³ M and the hydrogen compartment contains a platinum electrode, PH₂ = 1.00 atm , and a weak acid, HA, at an initial concentration of 1.00 M. If the observed cell potential is 0.340 V at 25ºC, calculate the Ka value for the weak acid HA.
a. 2.43 × 10⁻⁷
b. 3.55 × 10⁻⁸
c. 8.91 × 10⁻⁷
d. 3.21 × 10⁻⁶
