Question

In each of A-C, below, indicate whether: a) the statement is possible under the laws of thermodynamics; b) the statement violates the First Law; c) the statement violates the Second Law. In the case of a Second Law violation, circle the name of the scientist whose version of the second law is most simply and obviously broken. In each case there is a best name, but feel free to explain your choice. (Adapted from Bill Reinhardt.)

A. A novel and reversible heat engine absorbs 10 kJ of energy from a high temperature bath, performs 8 kJ of work on the surroundings, and exhausts 5 kJ of heat into a low temperature heat bath.

a. possible

b. violates First Law

c. violates Second Law: Kelvin Clausius Boltzmann

B. One night you wake up to discover that all the air in your room has gone under your bed. Note that this happens with no change in energy or temperature.

a. possible

b. violates First Law

c. violates Second Law: Kelvin Clausius Boltzmann

C. A novel & reversible heat engine absorbs 10 kJ of energy from a low temperature reservoir, performs 8 kJ of work on the surroundings, and exhausts 2 kJ of energy into a high temperature bath.

a. possible

b. violates First Law

c. violates Second Law: Kelvin Clausius Boltzmann

Answer 1

A. Violates first law.

The system recieves only 10kJ while it does 8kJ work and exhausts 5kJ. That is a total of 13kJ. So, the sytem recieves less energy than it gives off. Which is not possible because according to the first law, energy can neither be created nor be destroyed.

B. Violates the second law

The system (room) is isolated because there is no transfer of energy or mass. As all the air has gathered to a small volume. So, the entropy of system has decreased. But the second law states that the entropy of an isolated system van only increase spontaneously.

C. Possible.

Because

Energy given to the system = 10kJ

Energy lost by the system = 8+2 = 10kJ

So, it is possible.

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