In the Nernst equation, Ecell is related to which quantity?

• A. Temperature only
• B. E°cell
• C. The reaction quotient Q
• D. Activation energy

Answer: (C)

The main idea is that the cell potential at any moment is set by how far the reaction has progressed, encoded in the reaction quotient Q. The Nernst equation shows Ecell = E°cell − (RT/nF) ln Q, so Ecell directly depends on Q: increasing Q (more products) lowers Ecell, while decreasing Q (more reactants) raises Ecell. Temperature also influences how strongly Q affects Ecell through the RT/nF factor, and E°cell provides the baseline when Q = 1. Activation energy isn’t part of this relationship.