# Tag Info

Accepted

### How are the Van der Waals constants a and b related to each other?

Yes, they are certainly correlated as shown in the following plot based on data from the Wikipedia Van der Waals constants data page The correlation should not be entirely surprising: the covolume ...
• 22.7k
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### Confusion in Van der Waals Equation

The van der Waals equation is represented as such: $$\left(P + \frac{an^2}{V^2}\right)(V-nb) = nRT$$ Here, $P$ is the pressure of the container and $V$ is indeed the volume of the container. All the ...
• 1,247
Accepted

### Why London Dispersion force is attractive not repulsive

A simple demonstration in electrostatics can convince that London dispersion forces are attractive. Has your physics teacher shown "charging by induction"? Charging by induction video Now ...
• 41.9k
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### If a = 0 for a Van der Waals gas, what does that signify?

The simple answer is no. An "$a$" of zero simply means the attractive forces are so low that they don't affect the pressure of the gas in a measurable way. As Ivan Neretin mentioned in the ...
• 12.2k
Accepted

### Van der Waals real gas equation

Let me begin my discussion by first introducing the notion, using some intuitive model building, and will try to derive, or perhaps guess the van der Waals equation of state. The perfect gas ...
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### Are van der Waals coefficients independent of temperature?

The van der waals constant can be directly obtained from the critical temperature and pressure. We have, ${a = \frac{27 R^2 T_c^2} {64 P_c}}$ ${b = \frac{R T_c }{ 8 P_c}}$ Since, $T_c$ and $P_c$ ...
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### How are the Van der Waals constants a and b related to each other?

As Ivan writes $a$ and $b$ are independent, but it does not mean that they are not correlated; however, so are a child's shoe size and reading ability which clearly does not mean that buying a child ...
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### How are the Van der Waals constants a and b related to each other?

Just for curiosity, I also plotted a vs b using the same date set used by Buck Thorn. What I want to know is what is the correlation shown in Buck Thorn's plot and what are the two outliers clearly in ...
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Accepted

### Why is the van der Waals constant b of NH3 less than that of N2?

From a purely geometrical standpoint and using some simple assumptions the similarity and order of b parameters should not be all that surprising. For ammonia the longest distance in the molecule can ...
• 22.7k

### Why London Dispersion force is attractive not repulsive

I would add two points to MFarooqs' answer. First, I would emphasize that the basis for attractive van der Waals interactions is the polarizability of molecules. Polarizability is the property of ...
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1 vote

### Finding (∂U/∂V )T = n^2a/V^2 for a van der Waals gas

The more general equation you are looking for is called the thermodynamic equation of state. You can start from the differential form of U according to the 1st + 2nd laws of thermodynamics for pV work ...
• 22.7k

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