Question

The ideal gas, which is a model for gas used in constant volume gas thermometers, for which P = \(\rho\)RT. This equation illustrates that there are only ______________________ independent intensive thermodynamic properties for a simple fluid.

• A. one
• B. two
• C. three
• D. four

Hint:

Remember the State Postulate: "Two properties fix the state" for most simple systems you'll encounter in thermodynamics. This is why thermodynamic property diagrams (like P-V, T-S diagrams) are two-dimensional.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
This question relates to the State Postulate of thermodynamics. The State Postulate defines the number of independent properties required to completely fix the state of a simple thermodynamic system. A simple fluid (or a simple compressible system) is one that is not influenced by electrical, magnetic, gravitational, motion, and surface tension effects.
Step 2: Detailed Explanation:
The State Postulate states that the thermodynamic state of a simple fluid is completely specified by two independent, intensive properties.
The given equation of state for an ideal gas, \( P = \rho RT \), relates three intensive properties:


P (Pressure)
\(\rho\) (Density)
T (Temperature)
(R is the specific gas constant, which is a constant for a particular gas).
This equation shows that these three properties are not independent. If you specify the values of any two of them (for example, T and \(\rho\)), the value of the third property (P) is automatically determined by the equation. Therefore, only two of these properties can be varied independently to define the state of the gas.
Step 3: Final Answer:
For a simple fluid like an ideal gas, there are only two independent intensive thermodynamic properties.