The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called:

Options

A. cell potential
B. cell emf
C. potential difference
D. cell voltage

Explanation

To solve the question, we need to understand the definitions of the terms related to electrode potentials in electrochemistry.

### Step-by-Step Solution:

1. **Understanding Electrode Potentials**:
- Electrode potential refers to the ability of an electrode to gain or lose electrons when in contact with an electrolyte. Each electrode has its own potential based on its material and the reaction occurring at its surface.

2. **Defining the Context**:
- The question specifies that we are considering the difference in electrode potentials when no current is drawn through the cell. This is crucial because it indicates that we are looking at a state of equilibrium.

3. **Identifying the Terms**:
- The options given are:
- A) Cell potential
- B) Cell emf
- C) Potential difference
- D) Cell voltage
- We need to determine which of these terms specifically refers to the situation described in the question.

4. **Understanding Cell emf**:
- The term "emf" stands for electromotive force. It is defined as the maximum potential difference between two electrodes when no current is flowing. This is the intrinsic potential difference that drives the electrochemical reaction.

5. **Comparing with Other Terms**:
- **Cell Potential**: This term can refer to the potential difference when current is flowing, so it is not the correct answer.
- **Potential Difference**: This is a general term that can apply to any situation, not specifically when no current is drawn.
- **Cell Voltage**: Similar to cell potential, this term is often used when current is flowing through the cell.

6. **Conclusion**:
- Since the question specifically asks for the difference in electrode potentials when no current is drawn, the correct answer is **B) Cell emf**.

### Final Answer:
The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called **cell emf**.

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