Which equation is used to calculate Ecell from E°cell and Q at 25°C?

• A. ΔG° = -n F E°cell
• B. Ecell = E°cell - (0.05916/n) log Q
• C. Q = [products]/[reactants]
• D. n is the number of electrons transferred

Answer: (B)

The Nernst equation is what ties cell potential to the standard potential, the reaction quotient, and the number of electrons transferred under a given temperature. At 25°C, Ecell = E°cell − (0.05916/n) log Q. This form directly gives the actual cell potential from the standard potential, the amount of charge transferred, and how far the reaction has progressed through Q. The factor 0.05916 comes from RT/F at 298 K and makes the base-10 logarithm convenient for this temperature.

So this equation is the one that uses E°cell and Q to calculate Ecell. Other options relate to Gibbs free energy, the definition of Q, or the meaning of n, but they do not provide the direct Ecell expression at 25°C.