Plotting H2O Pressure vs Volume w/ Van Der Waals Gas Equation

In summary, it is important to keep in mind that the van der Waals equation is an approximation and to double check your calculations and plot with a wider range of values.
  • #1
ja87
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Homework Statement


i must use van der waals gas equation to plot a pressure against volume graph for H2O. i must do 3 plots on one graph, one of the critical temperature given a point of inflection, one where temperature is less than the critical temperature giving a large dip in the graph, and one where T>critical temperature and hence gives a a curve where dp/dv is never =0.


Homework Equations


i have the van der waals equation :(p+a(1/v)^2)*(v-b) = n*R*T
and have rearranged to make p=-(-a(1/v)^2*v+a(1/v)^2*b+n*R*T)/(-v+b)
i also have a=0.5507, b=3.04*10^-5, R=8.314, n=1

The Attempt at a Solution



i have tried to plot a p(v) graph with these values in this equation (using Maple) using small, large and negative values for T and all i get is a graph that looks like a 1/x graph, i cannot get the desired dip for when T<critical temperature. am i using the wrong equation or are my numbers wrong.
 
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  • #2


Thank you for your post. It seems like you are on the right track with using the van der Waals equation to plot a pressure vs. volume graph for H2O. However, there are a few things that may be causing your graph to not match your expectations.

Firstly, it is important to note that the van der Waals equation is an approximation for real gases and may not accurately represent the behavior of all gases, including H2O. Therefore, your graph may not perfectly match your expectations.

Secondly, it is important to double check your calculations and make sure you are using the correct values for a, b, R, and n. It may be helpful to double check your calculations with a different source or to ask a colleague to review them.

Finally, it may be helpful to plot your graph using a wider range of values for volume, as well as a wider range of temperatures. This may help to better visualize the behavior of the gas at different temperatures and volumes.

I hope this helps and good luck with your plotting!
 

1. What is the Van Der Waals Gas Equation?

The Van Der Waals Gas Equation is an equation that describes the behavior of real gases, taking into account intermolecular forces and the finite size of gas molecules.

2. Why is it important to plot H2O pressure vs volume with the Van Der Waals Gas Equation?

Plotting H2O pressure vs volume with the Van Der Waals Gas Equation allows us to better understand the behavior of water as a real gas, taking into account factors such as intermolecular forces and molecular size. This can provide more accurate and realistic data compared to ideal gas equations.

3. How is the Van Der Waals Gas Equation different from the Ideal Gas Law?

The Ideal Gas Law assumes that gas molecules have no volume and do not interact with each other, while the Van Der Waals Gas Equation takes into account the actual volume and attractive forces between gas molecules.

4. What factors affect the pressure vs volume relationship of H2O using the Van Der Waals Gas Equation?

The pressure vs volume relationship of H2O using the Van Der Waals Gas Equation is affected by the temperature, pressure, and volume of the gas, as well as the attractive forces between water molecules and the size of the water molecules themselves.

5. How do I use the Van Der Waals Gas Equation to plot H2O pressure vs volume?

To plot H2O pressure vs volume using the Van Der Waals Gas Equation, you will need to know the values for temperature, pressure, and volume of the gas. Then, you can plug these values into the equation and plot the resulting data points on a graph. Alternatively, you can use software or online tools to automatically plot the data for you.

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