Explanation:

The electrochemical cell stops working after some time because the electrode potential of both the electrodes becomes equal. This occurs due to various factors that affect the functioning of the cell.

1. Electrode potential:
Each electrode in the electrochemical cell has its own characteristic electrode potential. The electrode potential is the measure of the tendency of an electrode to gain or lose electrons. In an electrochemical cell, two different metals or materials are used as electrodes, and they have different electrode potentials.

2. Cell reaction:
The cell reaction is the chemical reaction that takes place in the electrochemical cell, generating an electric current. This reaction occurs due to the difference in electrode potentials between the two electrodes. The electrode with a higher electrode potential tends to lose electrons and undergo oxidation, while the electrode with a lower electrode potential tends to gain electrons and undergo reduction.

3. Equalization of electrode potentials:
Over time, as the cell operates and current flows, the electrode potentials of both the electrodes tend to equalize. This happens because the electrode with a higher electrode potential loses electrons and undergoes oxidation, which decreases its electrode potential. At the same time, the electrode with a lower electrode potential gains electrons and undergoes reduction, which increases its electrode potential. As a result, the difference in electrode potentials decreases, and eventually, they become equal.

4. Loss of potential difference:
When the electrode potentials of both the electrodes become equal, there is no longer a potential difference between them. This leads to the cessation of the cell reaction and the stoppage of the electric current. The cell is said to have reached equilibrium, where the electrode potentials are balanced, and no further reaction occurs.

5. Reversal of cell reaction:
In some cases, when the electrode potentials become equal, the cell reaction may even get reversed. This means that the electrode that was previously undergoing oxidation starts gaining electrons and undergoing reduction, while the electrode that was previously undergoing reduction starts losing electrons and undergoing oxidation. This reversal of the cell reaction further contributes to the stoppage of the cell's functioning.

In conclusion, the electrochemical cell stops working after some time because the electrode potential of both the electrodes becomes equal, leading to the loss of potential difference and the cessation of the cell reaction.