Question

The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called:
A. cell potential
B. cell emf
C. potential difference
D. cell voltage

Answer 1

Hint: We will at first look at the definition of electrode potential. When no current is drawn through the cell then the electrode potential is basically emf of the cell. Cell emf is the maximum potential difference between the two electrodes of a cell.

Complete step by step answer: Electrochemistry deals with the electrochemical cells and the electrode potential refers to the electromotive force of a cell. It appears at an interface between an electrode and electrolyte due to the transfer of charged species that are ions.
Basically, the electrode potential is the tendency of an electrode to lose or gain electrons when it is in contact with the solution of its own ions.
Electrode potential depends on the nature of the electrode, concentration of the ions, temperature.
There are different types of electrode potential depending upon the nature of the metal to lose or gain electrons.
- Oxidation potential: when electrodes possess negative charge with respect to the solution and oxidation takes place.
- Reduction potential: when electrode is positively charged and reduction occurs.
In the electrochemical cell, the cathode and anode have some electrode potential independently and the difference between them is what we call as cell potential.
- Cell potential that is $E_{cell}$ = $E_{cathode}$ - $E_{anode}$
- Cell emf is the energy provided by a cell or battery per coulomb of charge passing through it. It is a potential difference across the terminals of the cell when no current is flowing through the circuit.
- Potential difference is the amount of work to be done to move a unit positive charge from one point to another point. It does not remain constant.
So, the difference between the electrode potentials of two electrodes when no current is drawn through the cell is called cell emf.

So, the correct answer is “Option B”.

Note: The difference between the emf and the potential difference should be kept in mind. These two things are not the same, a slight difference is present. While emf is the maximum potential difference between the electrodes, the potential difference is the difference between any two points of a closed circuit.