1. The problem statement, all variables and given/known data Calculate the variation of entropy in the following processes: a) Heating of 18 kg of water from 15 to 40ºC at ambient pressure. b) Compression of 9 kg of water from ambient pressure to 7atm at the temperature of 15ºC. 2. Relevant equations ΔS=Cp*ln(T_final/T_initial) 3. The attempt at a solution So for a) I checked the Cp of water getting 4.18KJ/kgºK and multiplied it by the 18 kg. Then I tried to apply the formula with the Cp and the Tfinal=313.15K and TInitial=288.15K and I think it is correct. For b) I think I have to use ΔS=R ln (P1 / P2) but I'm not sure. And if it is that expression, the Pressure must be in kPa?