The plot of x/m versus temperature at constant pressure is called 

Options

A. adsorption isotherm
B. adsorption isobar
C. adsorption isochore
D. Freundlich isotherm

Answer

To solve the question regarding the plot of \( \frac{x}{m} \) versus temperature at constant pressure, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Variables**:
- In the expression \( \frac{x}{m} \), \( x \) typically represents the amount of adsorbate (the substance being adsorbed), and \( m \) represents the mass of the adsorbent (the material on which adsorption occurs).
- The plot involves temperature on one axis and \( \frac{x}{m} \) on the other.

2. **Identifying the Conditions**:
- The question specifies that the plot is made at constant pressure. This is a crucial detail because it indicates the type of thermodynamic process we are dealing with.

3. **Understanding the Terminology**:
- **Isotherm**: A plot where temperature is held constant.
- **Isobar**: A plot where pressure is held constant.
- **Isocore**: A plot where volume is held constant.
- **Front-leach isotherm**: This term is less common and typically relates to specific adsorption processes.

4. **Applying the Definitions**:
- Since the plot of \( \frac{x}{m} \) versus temperature is made at constant pressure, it aligns with the definition of an **adsorption isobar**. This is because we are observing how the adsorption changes with temperature while keeping the pressure constant.

5. **Conclusion**:
- Therefore, the correct answer to the question is that the plot of \( \frac{x}{m} \) versus temperature at constant pressure is called an **adsorption isobar**.

### Final Answer:
The plot of \( \frac{x}{m} \) versus temperature at constant pressure is called **adsorption isobar**.