Answer: 3R.
- A R
- B 2R
- C 3R
- D 4R
Correct answer: C. 3R
Explanation: Dulong-Petit law: Cv = 3R per mole for most solid elements at room temperature (6 degrees of freedom, each contributing R/2).
The Carnot cycle alternates two isothermal steps (heat absorbed at TH, released at TC) with two adiabatic steps (no heat exchange); the enclosed loop area equals the net work output, and η = 1−TC/TH is the maximum possible efficiency between those two temperatures.
Concept context
Laws of thermodynamics, heat engines, entropy, and gas processes.