Assertion : Current stops flowing when `E_(cell)=0`.
Reason : Equilibrium of the cell reaction is attained.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion .
B. If both assertion and reason are true but reason is not the correct explanation of assertion .
C. If assertion is true but reason is false .
D. If both assertion and reason are false .

Answer

To solve the question, we need to analyze the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "Current stops flowing when \( E_{cell} = 0 \)." This means that when the electromotive force (EMF) of the electrochemical cell is zero, there is no net movement of charge, hence no current.

**Hint**: Think about what happens to the flow of electrons in a circuit when there is no potential difference.

2. **Understanding the Reason**: The reason given is that "Equilibrium of the cell reaction is attained." At equilibrium, the forward and reverse reactions occur at the same rate, and there is no net change in the concentrations of reactants and products.

**Hint**: Consider the concept of equilibrium in chemical reactions and how it relates to the potential difference in electrochemical cells.

3. **Relationship Between Gibbs Free Energy and EMF**: The relationship between the Gibbs free energy change (\( \Delta G \)) and the cell potential (\( E_{cell} \)) is given by the equation:
\[ \Delta G = -nFE_{cell} \]
At equilibrium, the change in Gibbs free energy (\( \Delta G \)) is zero. Therefore, when \( \Delta G = 0 \):
\[ 0 = -nFE_{cell} \implies E_{cell} = 0 \]

**Hint**: Recall how Gibbs free energy relates to spontaneity and how it connects to the EMF of a cell.

4. **Conclusion**: Since both the assertion and the reason are true, and the reason correctly explains why the assertion is true, we conclude that both statements are valid.

**Hint**: Reflect on how assertions and reasons are evaluated in logical statements.

5. **Final Answer**: Therefore, the correct option is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

### Summary:
- **Assertion**: Current stops flowing when \( E_{cell} = 0 \) (True).
- **Reason**: Equilibrium of the cell reaction is attained (True).
- **Conclusion**: Both statements are true, and the reason explains the assertion.