# Van der Waals Equation, Virial Expansion

## Homework Statement

Taken from Concepts in thermal Physics:

## The Attempt at a Solution

Shouldn't the van der waal's equation be:

$$p = \frac{RT}{V_m -b} - \frac{a}{V_m^2}$$
$$pV_m = \frac{VRT}{V_m -b} - \frac{a}{V_m}$$

TSny
Homework Helper
Gold Member
Shouldn't the van der waal's equation be:

$$p = \frac{RT}{V_m -b} - \frac{a}{V_m^2}$$

Yes. So (26.41) has a wrong sign. But it looks like they got it right in (26.42) and (26.43).

1 person
Chestermiller
Mentor

## Homework Statement

Taken from Concepts in thermal Physics:

## The Attempt at a Solution

Shouldn't the van der waal's equation be:

$$p = \frac{RT}{V_m -b} - \frac{a}{V_m^2}$$
$$pV_m = \frac{VRT}{V_m -b} - \frac{a}{V_m}$$

You're right. It sure looks like they made a slew of algebra mistakes. The first term on the right hand side of 26.41 isn't even dimensionally correct.

Chet

1 person
TSny
Homework Helper
Gold Member
You're right. It sure looks like they made a slew of algebra mistakes. The first term on the right hand side of 26.41 isn't even dimensionally correct.

Chet

Right. I didn't notice that they should not have had the factor of V on the left side of equation 26.41.

#### Attachments

• van.png
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