# Formula Van der Waals Equation Pressure    Temperature    Covolume    Cohesion parameter    Gas constant

## Pressure

Unit
Pressure of the (real) gas. With the real gas - in contrast to the ideal gas - the gas pressure may be very high.

## Temperature

Unit
Temperature of the (real) gas. With the real gas - in contrast to the ideal gas - the temperature of the gas may be low.

## Volume

Unit
Volume of the (real) gas. Molar volume: $$V_{\text m} ~=~ \frac{V}{n}$$.

## Amount of substance

Unit
Amount of substance indirectly indicates the number of particles of the gas.

## Covolume

Covolume is the material-dependent intrinsic volume of the particles of the real gas. It reduces the volume $$V$$ available for the motion of the particles to $$(V ~-~ n\,V_{\text b})$$. For the ideal gas, the following holds: $$V_{\text b} ~=~ 0$$. The unit of covolume is $$\mathrm{m}^3 / \mathrm{mol}$$.

## Cohesion parameter

Cohesion parameter is a material-dependent quantity that indicates the force between the particles of the gas. In the case of an ideal gas, the following holds true: $$a ~=~ 0$$. The term $$\frac{n^2 \, a}{V^2}$$ is called internal pressure. The unit of the cohesion parameter is $$\mathrm{Pa}\,\mathrm{m}^6 / \mathrm{mol}^2$$.

## Gas constant

Unit
Gas constant is a physical constant with the value: $$R = 8.314 \, \frac{\text J}{\text{mol} \, \text{K}}$$.