If using the H+/H2 couple to estimate pH at a fixed state, which relation is typically used at 25 C?

• A. pH ≈ E / 0.05916
• B. pH ≈ -E / 0.05916 at 25 C (for the H+/H2 couple where E° = 0 V)
• C. pH ≈ -E / 0.05916 at 25 C (for the H+/H2 couple where E° = 0 V)
• D. pH cannot be estimated from redox potentials.

Answer: (C)