Van der Waals Gas Isotherms: Plotting with Maple

[ja87]

i have to plot isotherms using the van der waals gas theory. i am using Maple to do this but no matter how many different equations i use i cannot get the graphs to look right. it should look like a 1/x curve but with a sharpe trough in it, but all can get is a graph that looks like a normal 1/x curve. does anyone know the equation i should use to give me the curve of pressure against volume for different values of temperature.

 

[Gokul43201]

1. Henceforth, post such questions in the Homework & Coursework subforums.
2. Write down the equation you are using to plot the isotherms
3. What values have you assigned to the coefficients, b and a?
4. You may simply be looking at the isotherms above the critical temperature. Have you chosen values of T that are very small?

 

[sir-pinski]

The equation you should use to plot isotherms for a van der Waals gas is the van der Waals equation, which takes into account the attractive and repulsive forces between gas molecules. It is given by:

(P + a/V^2)(V - b) = RT

Where:
P = pressure
V = volume
T = temperature
a and b are constants specific to each gas

To plot the isotherms, you can use the "plot" function in Maple and specify the range of values for pressure and volume. For example, to plot the isotherms at different temperatures, you can use a loop and vary the temperature in the equation above.

It is important to note that the shape of the isotherms will depend on the values of a and b, which are specific to each gas. In general, for a van der Waals gas, the isotherms will have a sharper trough compared to the ideal gas isotherms due to the attractive forces between molecules. However, for some gases, the shape of the isotherms may not be very different from the ideal gas isotherms.

If you are still having trouble getting the desired curve, you can try adjusting the values of a and b to see how they affect the shape of the isotherms. You can also refer to the literature or consult with a professor or a tutor for assistance.