Work done by a van der waal gas/real gas in a expansion

In summary, the formula for work done by a van der Waals gas in an isothermal reversible expansion is attached in the JPG file. However, finding the work done in an isothermal irreversible expansion, where the real gas expands against a constant pressure (such as in a balloon), may not have an analytic expression. The process for this expansion involves dropping the pressure and then holding it at the new state until the system equilibrates.
  • #1
Zachary96
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Edited: To summarize the below attached jpg file is the formula for work done by a van der waals gas in a isothermal reversible expansion.

Is there a way to find the work done by a van der waal gas in a isothermal irreversible expansion? i.e the real gas expands against a constant pressure (in a balloon)
 

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  • #2
Sure. But you may not be able to get an analytic expression. You drop the pressure from pi to pf at time zero, and then you hold the pressure at pf until the system equilibrates at the new state. It this the process you are envisioning?
 

1. What is the definition of work done by a van der Waals gas in an expansion?

The work done by a van der Waals gas in an expansion is the amount of energy transferred to the surroundings as the gas expands against external pressure. This work is a result of the gas molecules interacting with each other and the container walls.

2. How is the work done by a real gas different from an ideal gas in an expansion?

The work done by a real gas is different from an ideal gas in an expansion because real gases have non-negligible molecular sizes and intermolecular forces, which affect their behavior. In contrast, ideal gases are assumed to have no molecular size and no intermolecular forces.

3. What factors influence the work done by a van der Waals gas in an expansion?

The work done by a van der Waals gas in an expansion is influenced by the initial and final volumes, the external pressure, and the van der Waals constants for the specific gas. These constants take into account the molecular size and intermolecular forces of the gas.

4. How is the work done by a van der Waals gas related to its internal energy?

The work done by a van der Waals gas is related to its internal energy through the first law of thermodynamics, which states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system. In the case of an expansion, the work done by the gas decreases its internal energy.

5. Can the work done by a van der Waals gas ever be negative in an expansion?

Yes, the work done by a van der Waals gas can be negative in an expansion. This occurs when the external pressure is lower than the internal pressure of the gas, causing the gas to do work on its surroundings and decrease its internal energy. This is known as an isothermal expansion.

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