PV Diagram of a monoatomic gas and diatomic gas

In summary: IKARAN: In summary, the conversation discusses a question on a previous test about drawing a PV diagram for a monoatomic ideal gas undergoing an isothermal compression and adiabatic expansion. The question also asks about the implications of a diatomic gas and its internal energy on the diagram. The main difference between the two gases is their heat capacities, leading to different changes in internal energy. The adiabatic condition PV^gamma = K is used to determine the expansion path for the diatomic gas.
  • #1
Zenderson3
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I'm reviewing a question on a previous test but am having trouble finding the solution for it.

We were told to draw a PV diagram of a monoatomic ideal gas that undergoes an isothermal compression from Va to Vb and then is allowed to expand adiabatically and quasistatically back to Va again.

I was able to comprehend this portion of the question fine but then got stuck on the next part that asked how this sketch would look if the molecule was diatomic. Aside from the difference in internal energy due to the degrees of freedom of a diatomic molecule I can't seem to find any other major implications of a monoatomic gas vs. a diatomic gas. Furthermore I can't seem to figure out how the internal energy of the system would tie into this diagram.
 
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  • #2
Zenderson3 said:
I'm reviewing a question on a previous test but am having trouble finding the solution for it.

We were told to draw a PV diagram of a monoatomic ideal gas that undergoes an isothermal compression from Va to Vb and then is allowed to expand adiabatically and quasistatically back to Va again.

I was able to comprehend this portion of the question fine but then got stuck on the next part that asked how this sketch would look if the molecule was diatomic. Aside from the difference in internal energy due to the degrees of freedom of a diatomic molecule I can't seem to find any other major implications of a monoatomic gas vs. a diatomic gas. Furthermore I can't seem to figure out how the internal energy of the system would tie into this diagram.
The same work is done on or by the gases during the compression and expansion parts. But their heat capacities are different. So their changes in internal energies in the isothermal compression part will be different which means that their final internal energies will differ.

The adiabatic condition: [itex]PV^\gamma = K[/itex] applies during the adiabatic expansion. Use this to determine how the adiabatic expansion path for the diatomic gas will compare to that of the monatomic gas.

AM
 

1. What is a PV diagram and how is it used?

A PV diagram is a graphical representation of the relationship between pressure (P) and volume (V) of a gas. It is used to analyze the thermodynamic processes undergone by a gas and to calculate its work, heat, and change in internal energy.

2. How does the PV diagram of a monoatomic gas differ from that of a diatomic gas?

A monoatomic gas contains single atoms, while a diatomic gas contains two atoms bonded together. This difference in molecular structure affects the shape of the PV diagram. The PV diagram of a monoatomic gas is a straight line, while that of a diatomic gas is a curve with a flat region at high pressures.

3. What does the area under the PV curve represent?

The area under the PV curve represents the work done by the gas. It is calculated by multiplying the pressure and volume changes during a process.

4. How does the PV diagram of a gas change during different thermodynamic processes?

The PV diagram of a gas can change depending on the type of process it undergoes. For example, during an isothermal process, the PV curve is a hyperbola. During an adiabatic process, the PV curve is steeper. And during an isobaric process, the PV curve is a straight horizontal line.

5. What are the applications of PV diagrams in real-life scenarios?

PV diagrams are used in various fields such as engineering, meteorology, and environmental science to analyze and predict the behavior of gases. They are also used in the design and operation of engines, refrigerators, and other devices that involve the expansion or compression of gases.

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