ETS Major Field Test Chemistry Practice Test 2026 – Complete Preparation Guide

In the van der Waals equation, the parameters 'a' and 'b' are specifically designed to account for the real behavior of gases, which deviates from the ideal gas laws. The parameter 'a' corresponds to the attractive forces between gas molecules. It adjusts for the interactions that occur when molecules are close together, which affect the pressure exerted by a gas in a container. A larger value of 'a' indicates stronger intermolecular attractions, leading to greater corrections in pressure.

The parameter 'b', on the other hand, represents the volume occupied by the gas molecules themselves. It is the volume exclusion factor that accounts for the finite size of the molecules, meaning that 'b' corrects the total volume available for the gas to occupy by subtracting the volume occupied by the actual molecules.

Together, these parameters provide a more accurate representation of a real gas's behavior under various conditions, improving upon the ideal gas law by incorporating factors that influence gas pressure and volume at the molecular level.