One or more options correct
A Daniell-type cell has at . Take . Which of the following statements is/are correct?
- A. With and the cell emf is about .
- B. With and the cell emf is lower than .
- C. The equilibrium constant of the cell reaction at lies between and .
- D. Doubling the surface area of both electrodes at fixed concentrations doubles the emf of the cell.
Show answer and solution
Answer: A
The cell reaction is with , so . Option A: , so , correct. Option B: , so , which is higher than , so B is wrong. Option C: , so , which is outside the stated range, so C is wrong. Option D: emf is an intensive property fixed by and the concentrations, and electrode area changes only the current capacity, so D is wrong. Only A is correct. As a further check on the structure of the problem, remember that the Nernst correction depends only on the reaction quotient , so any change that lowers raises the emf, and the emf falls to zero only when equals , that is, at equilibrium.
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