# Cubic EoS - only VAPOR root is converging o_o

• maistral
In summary, the conversation discusses the speaker's attempt to generate a VLE graph for ethylene oxide-water using SRK. They mention that the vapor root is converging, but the liquid root is not. Upon further inspection, they notice that the two roots converge in the complex domain, and question if this has any physical meaning. They are also inquiring if there are any new findings or additional information to share.
maistral
Hello. I would like to inquire as to how to deal with the said topic title.

I'm trying to generate a VLE graph for ethylene oxide-water. While I know that EO will quickly vaporize since the boiling point of EO is quite low, I'm still trying to generate a VLE using SRK.

So while the vapor root is converging, the liquid root won't.

Upon inspection (and using taylor expansion of the third degree to simplify the equation), I noticed that the two roots (the liquid root and the useless middle root) converge in the complex domain. Does this have a physical meaning?

I'm sorry you are not generating any responses at the moment. Is there any additional information you can share with us? Any new findings?

## 1. What is Cubic EoS?

Cubic EoS (Equation of State) is a thermodynamic equation used to calculate the properties of gases, such as pressure, volume, and temperature, based on the gas' molecular interactions.

## 2. How does Cubic EoS differ from other EoS?

Cubic EoS uses a cubic polynomial to model the behavior of gases, while other EoS may use different equations or models. Cubic EoS is particularly useful for studying the behavior of gases at high pressures and low temperatures.

## 3. Why is the vapor root the only one converging in Cubic EoS?

In Cubic EoS, there are three possible roots or solutions to the equation. However, at certain conditions, only the vapor root will converge or provide a meaningful solution. This is due to the specific characteristics of the cubic equation and the properties of gases at different conditions.

## 4. What factors can affect the convergence of the vapor root in Cubic EoS?

The convergence of the vapor root in Cubic EoS can be affected by various factors, such as the nature of the gas (polar or non-polar), the pressure and temperature of the system, and the accuracy of the input parameters used in the equation.

## 5. How is Cubic EoS useful in scientific research?

Cubic EoS is a valuable tool in scientific research, particularly in the fields of thermodynamics, fluid mechanics, and chemical engineering. It allows scientists to accurately predict the behavior of gases under different conditions, which is crucial in designing and optimizing processes and systems in various industries.

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