1.6 moles of an ideal gas with Cv,m = 3R/2, initially confined to a container of volume 2 litre and at a temperature 47 °C, expand (or are compressed) against a constant external pressure of 0.7 atm until the final pressure of the gas is equal to the external pressure and the final temperature of the gas is equal to the temperature of the surroundings. During this process the system does 1,556 J of work on the surroundings. Calculate the change in entropy, ΔS, of the gas (in J / K).