Question

What is the physical significance of van der Waals constant a and b?

Answer 1

• van der Waals equation is the relationship between the pressure, volume, temperature, and amount of real gases.
• For a real gas containing ‘n’ moles, the equation is written as: $(\mathrm{P}+\frac{{\mathrm{an}}^2}{{\mathrm{V}}^2})(\mathrm{V}-\mathrm{nb})=\mathrm{nRT}$

where, $\mathrm{P}$ = Pressure of a gas

$\mathrm{R}$ = Gas constant

$\mathrm{V}$ = Volume of a gas

$\mathrm{n}$= Number of moles of a gas

$\mathrm{T}$= Temperature

$\mathrm{a},\mathrm{b}$ = constant

The physical significance of $\mathrm{a}$ and $\mathrm{b}$:

• The constant “$\mathrm{a}$” is the measure of the magnitude of intermolecular attractive forces between the particles. It provides a correction for the intermolecular forces.
• The constant “$\mathrm{b}$” measure the volume of a gas molecule. It provides the correction for infinite molecular size and its value is the volume of one mole of the atoms or molecules.