The constant b in van der Waals equation of state is a correction for what?

The constant b in van der Waals equation of state is a correction for what?

• A. Intermolecular forces
• B. Temperature
• C. Pressure
• D. Volume occupied by the molecules of the gas

Answer: (D)

The term b represents the finite size of the gas molecules—the volume they occupy and thus exclude from the space available to other molecules. In the van der Waals equation, you see the volume term written as (V − nb); here nb is the total volume effectively unavailable because each mole of molecules takes up some space. This reduces the free volume that the molecules can move in, which is why real gases don’t behave like ideal gases at high pressures or low volumes. The other correction in the equation handles attractive forces between molecules (that one is represented by a), and temperature is a variable in the equation rather than a correction term for volume. So the constant b is all about the volume occupied by the molecules themselves.

The term b represents the finite size of the gas molecules—the volume they occupy and thus exclude from the space available to other molecules. In the van der Waals equation, you see the volume term written as (V − nb); here nb is the total volume effectively unavailable because each mole of molecules takes up some space. This reduces the free volume that the molecules can move in, which is why real gases don’t behave like ideal gases at high pressures or low volumes. The other correction in the equation handles attractive forces between molecules (that one is represented by a), and temperature is a variable in the equation rather than a correction term for volume. So the constant b is all about the volume occupied by the molecules themselves.