While an ideal gas expands at constant temperature there is no change in molecular kinetic energy KE is proportional to temperature, as well as there is no cange in potential energy due to intermolecular attractions these are zero for ideal gases. Therefore for isothermal constant temperature expansion of an ideal gas, deltaE=0. Presume we allow an ideal gas to expand isothermally from 2.50L to 5.50L in two steps:
a) Against a constant external pressure of 3.50atm until equilibrium is reached then (b) against a constant external pressure of 2.50atm until equilibrium is reached. Compute q and w for the two step expansion.