Chemistry - Thermodynamics - II Question with Solution | TestHub

Option B is correct: A cycle with only one isothermal process would absorb heat from a single reservoir and convert it entirely into work, which directly violates the Second Law of Thermodynamics (Kelvin-Planck statement).

Option C is correct: The efficiency of a Carnot engine ($\eta =1-T_C/T_H$) depends strictly on the temperatures of the hot and cold reservoirs, making it completely independent of the working fluid (ideal or real gas).

Option D is correct: The First Law for an open system accounts for control volume energy changes, which inherently depend on mass exchange and the flow energy (enthalpy) carried by that mass.