Which of the following is not a thermodynamic coordinate ?

Options

A. P
B. T
C. V
D. R

Answer

To solve the question "Which of the following is not a thermodynamic coordinate?" we need to analyze the given options: pressure, temperature, volume, and R (the gas constant).

### Step-by-Step Solution:

1. **Understand Thermodynamic Coordinates**:
- Thermodynamic coordinates are variables that describe the state of a thermodynamic system. Common thermodynamic coordinates include pressure (P), volume (V), and temperature (T).

2. **Identify the Options**:
- The options provided are:
- A) Pressure
- B) Temperature
- C) Volume
- D) R (Gas Constant)

3. **Analyze Each Option**:
- **Pressure (P)**: This is a thermodynamic coordinate as it describes the force exerted by gas particles in a given area.
- **Temperature (T)**: This is also a thermodynamic coordinate, representing the average kinetic energy of particles in the system.
- **Volume (V)**: This is another thermodynamic coordinate, indicating the space occupied by the system.
- **R (Gas Constant)**: The gas constant (R) is a constant value used in equations of state, such as the ideal gas law. It has a fixed value (approximately 8.314 J/(mol·K)) and does not vary with the state of the system.

4. **Conclusion**:
- Since pressure, temperature, and volume are all variables that can change and describe the state of a thermodynamic system, while R is a constant, we conclude that R is not a thermodynamic coordinate.

5. **Final Answer**:
- The correct option is D) R (Gas Constant).