Question

A graph is plotted for a real gas which follows Van der Waals equation with $P{V}_m$ taken on y-axis and P on x-axis. Find the intercept of the line where $V_m$ is the molar volume.

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

For a real gas, the plot of pVm vs. p can be of two types A or B, but at the point of intercept, that is, p = 0 or when p is low, Van der Waals equation reduces to ideal gas equation PV = nRT. For 1 molar, comparing $P{V}_m$ = RT with y = mx + C, we get the intercept on y-axis as RT

For both A and B, at very low pressure P the real gas equation gives RT as the intercept (n = 1 mol)