Final answer:
The entropy of the steam at the exit of an adiabatic nozzle likely increases because the expansion process is typically irreversible, even though no heat is transferred. so, option c is the correct answer.
Step-by-step explanation:
When steam is accelerated through an adiabatic nozzle, no heat is added or removed from the system, indicating that it is an adiabatic process. According to the second law of thermodynamics, for an adiabatic process, the entropy of a system can either remain constant, in the case of a reversible process, or increase, in the case of an irreversible process. Because steam expansion through a nozzle is typically an irreversible process due to friction and other non-ideal factors, the entropy of the steam at the nozzle exit is likely to increase. Therefore, the correct answer is c. Increases; No heat transfer.
In an adiabatic process where no heat is transferred, the entropy of the steam will increase at the nozzle exit. This is because there is an irreversible process happening, resulting in an overall increase in entropy for the system. With respect to entropy, there are only two possibilities: entropy is constant for a reversible process, and it increases for an irreversible process.