In a concentration cell based on the same redox couple, how does increasing temperature affect Ecell?

• A. Ecell is independent of temperature
• B. Ecell increases with temperature because Ecell ≈ (RT/nF) ln(C2/C1)
• C. Ecell decreases with temperature because RT reduces at higher T
• D. Ecell becomes zero at high temperature

Answer: (B)

In a concentration cell, the emf comes from a difference in ion concentrations, and the Nernst equation shows how temperature affects it. For a cell based on the same redox pair, the emf can be written as Ecell = (RT/nF) ln(C2/C1). Here, R and F are constants, so the temperature dependence is through RT. As temperature increases, RT grows, so the magnitude of Ecell increases for a fixed concentration ratio. If C2 > C1, the emf is positive and grows larger in magnitude with temperature; if C2 < C1, it’s negative and becomes more negative in magnitude. The emf is zero only when the two concentrations are equal, not just at high temperature.