What value of P2 would make ∆S=0 for this process?

Question

Suppose that H2O (liquid) goes from 29°C and 1 atm to 31.0°C and P_2. What value of P_2 would make ∆S=0 for this process? State any approximations made.

Answer 1

By raising the water temperature do you really have an isentropic process (reversible adiabatic) ? Can you add or remove heat or PV energy during an adiabatic process ?
I do not believe there would be a process at all other than adding heat to warm the water. Any increase of pressure is moot. In an adiabatic throttling process to a lower pressure the temperature would drop. This temperature did not.
There is no answer.