Question

Two moles of an ideal gas are cooled isochorically and then expanded isobarically to lower the gas temperature back to the initial value. Find the entropy increment of the gas if in this process the gas pressure changed n = 3.3 times.

Answer 1

The entropy change depends on the final & initial state only, so we can calculate it directly along the isotherm, it is ΔS = 2R In  n = 20 J/°K 
 (assuming that the final volume is n times the inital volume)